The AM Forum

Over in this thread - http://amfone.net/Amforum/index.php?topic=37139.new#new (http://amfone.net/Amforum/index.php?topic=37139.new#new) it was learned that I acquired a Hammer-land BC-799/SP-200 receiver. One I absolutely do NOT NEED. Or to be more precise, yet another radio needing work that I ought to know better than to bring anywhere near my shack.

Given that I have not yet finished all sorts of other radios and gear, test equipment, why should this one be any different?

It sort of is, because I had already made a running start at another one of these, acquired a few years back, in genuine rust-o-bucket condition. It was cheap. Yes. Cheap. The weak point of almost all hams.

So I had taken the front panel off, since it is engraved (stamped probably) stripped it of paint using "green" stripper (which worked surprisingly well). Was surprised to see that the steel front panel was actually nickel plated! Thanks to years of hard living the panel had quite a few scratches and dings. This meant bondo, sand, bondo, sand, primer, sand, spot primer, sand, and well it still had some tiny little pinholes. BAH!

This I set aside in a place of high honor, in the front area of the shack. Where it sat for the past several years. Mocking me.

After all those hours trying to get the surface flat and smooth. It sat there mocking me, all the same.

Oddly enough, as anyone who has visited this QTH will attest, it's generally a chaotic situation. Too much stuff, not enough space. The factor is now like 4:1 in favor of stuff. The oddly part is that when it comes to building things or repairing things I become nearly an obsessive perfectionist. So this panel was just NG. Not even close to perfect.

And, you know what? IF it was perfect? Throwing the paint, would have resulted in a wonderfully smooth glassy gloss finish, until the wet paint runs... sand, paint again...

Well the image attached is/was the inspiration. Now, I forget who did this. Whomever it was/is, please chime in and take credit! Of course that one is/was an SP-600 which has style. Maybe not the best receiver ever, but eye candy!

So I was going to do up the panel in a neat metallic color. Was going to pick another color, but did not have the inspiration on that. Besides, it was sitting there mocking me. Pinholes.

Anyhow, when Steve W2TRH got this BC-799 and it ended up here, I thought <hey I've got a PANEL for this already!>. I grabbed the paint and shot it, a nice metallic cranberry red auto paint. Yes I did. Pinholes and all!

----------

Then too I realized that this is still not going to be all honey and roses. The unit is stone cold deaf on all but one range, and is going to need to be gone through. Somebody had tried to recondition it and obviously got up to a point and no further. It's possible that the previous owner is going to see this post too.

My thinking is that I ought to take pix and do a blog as it goes along. We see a few before and after here, and of course people asking questions and getting answers. But not too much of the doing and the process shows up.

I'm going to try, for better or worse to document with pix and text whatever I do on this radio. Hopefully it will inspire and maybe even start a trend. Otoh, I might get waylaid and stalled, and this might end up being not much of anything. But, I'm going to try to do what I can, and we'll see how it goes...

Here's the receiver's front panel, as found.

The second shot - somewhat out of order as far as introducing the unit, shows the "tuning coils" from the bottom, with the cover plate removed.

The way this radio's front end works is that it has what amounts to two cascaded sections of tuned filters that track as you tune the radio. I'd expect that these are fairly wide. The one to the left in the photo is the same sort of coil that tunes, but this one is the "HF OSC", and amounts to a VFO.

Going to get back into this shortly.

Since the radio is stone deaf on all but the 10-20mc range, all of these stages will need to be checked out.

My plan is to grab an RF sig generator and input signal "in band" and see if it can be followed with a scope from stage to stage, down to the mixer. If one band works, then the mixer works.

The other half of this is to check the function of the "HF OSC" section. If the HF OSC is not functioning, the receiver won't tune or hear anything. That will be watching the output starting with the working band, and switching bands. If it doesn't work, then check the coils for continuity, then check the caps. Each stage has a series cap...

That's the idea.

 

   The information provided on this site may prove helpful..

http://www.radioblvd.com/hammarlund_super_pro.htm

  For the LO, I usually just use another RX. You can hear
em' loud and clear across the bench..

GL

/Dan

Dan,

Thanks. Think I will give it a shot and fire up another receiver! :D
Heh.
Appreciate all the help.

Yes, I think I have found all the sites by now.

While cruising I came across this site with a recondition on a National.
Although he doesn't show more than the before and after, it's got to be one of the most
impressive clean ups I've seen online.  http://www.ohio.edu/people/postr/bapix/nc120rao.htm (http://www.ohio.edu/people/postr/bapix/nc120rao.htm)

This is my first time into a Hammarlund. Except for the eye-candy aspects of the SP-600 and the TMC GPRs I've not been very interested in them at all. Not sure what the sudden desire is all about.

Probably has more to do with the paint on the front panel than the radio itself!

Of course a whole ton of folks have been into these receivers. I'm late to the party for certain. Expected on my side are stupid mistakes and misunderstandings as I go along, assuming I can keep this going... but that's part of it.  the idea is more to document the process and steps along the way than to provide any sort of "definitive guide."

The previous owner, as I mentioned got just so far, and maybe got frustrated or stuck, sold the rig. I'm hoping this comes out as more of "how to get it done" rather than exactly what to do, the general plan of action, and an overview including talking about it and the thought process along the way. Like now. :D

Today I'll be checking the rusto-o-bucket rig to see what it really is, and what it covers. If I'm lucky I can "borrow" some coils.

Also picking up:
- "Magic Eraser"
- Goop (waterless hand cleaner)
- 409 + Ammonia
- Extra toothbrush

This is in preparation for cleaning the chassis, etc... the chassis has been cleaned a bit by the previous owner.

I'll be very curious to see how this magic eraser thing works. Found out that it is melamine foam!! Micro sized pores and fibers. Might be the ultimate thing for this sort of thing.

The other items are highly recommended and oft cited by folks who have posted restorations online, and by some here as well. The Magic eraser is new.

I'll also be trying out some other chemical preparations and applicators - on a "mule" chassis first.

Later that same day, our hero and Spotty the RF dog...

... I picked up some brand X "magic eraser" thingies. That and a can of NEVRDULL. The GOOP, actual GOOP brand, and some extra toothbrushes at the dollar store.

Checked the rust-o-bucket rig, and it is the same one, with the useless VLF bands. Drat!

But got a lead on a 1004, which has the "good" bands. Might come through eventually. Also have access to a few NOS coils for the aforementioned "useless VLF bands" that might just get rewound if it comes to that.

So, it might not ever work, but it ought to look shiny!  ::)

Also grabbed an RF sig gen off the shelf...

                    _-_-

Well, you have to look carefully. Never know what you will find, or who has been where.

Looking down at the top of the tuning assembly, on the bandspread side, using some bright lights, noticed something was not looking quite right. two wires not touching? More inspection showed that three of these wires were clipped, one per section. Huh?

Without tracing the circuit to see what these were, was this the cause of the dead bands? Re-solded them - ok it's a "temporary" fix. I do not like a butt soldered connection. But no, this is not the cause.

Why were they clipped? Dunno, they are associated with the bandspread variable cap.

  Maybe someone bent the rotor plates and shorted it out.
Visual inspection or an ohmmeter while turning it across it's
full range may tell the tale.

/Dan

  I found this little "Blurb" in the TM...

/Dan

Dan,

Yes, possible.

I did run the radio after I reconnected them, and of course they may only be used on one or more bands... but the 10-20mc band worked as before.

I'll use the Arrf generator to determine the calibration of that band - as in, is it anywhere near where it should be. And then to see if there is any life on the other bands.

I'll also be trying to see if I can hear the HF osc on the bench receiver too.
Maybe even later tonight.
That was a really good tip.

After these preliminary diagnostics what to do next will be considered. It looks likely, based on what I saw on one of the websites, that I'll end up pulling the entire tuner assembly out anyhow. I've got to repair the band indicator on the main dial side - probably replace it with one from the rust-o-matic unit, the one in this one has a bend in it (how the heck did that happen??). Makes the band switching not so great.

Also cleaning the chassis surface will be far easier.

We'll see...

So, I got the stuff to clean. Mostly things recommended by others on their websites where they did restorations.

Attached is the test.
I did it on the bottom plate.

The right hand upper set is Amonia + 409 with and without scrubbers, including the magic eraser (not terribly impressed, btw).

The upper two left are NEVR-DULL applied top with the magic eraser, and below that with the wadding.

Lowest right is the winner.
I did a better job with it on the lowest right, but that was after I took the pic, and you can't see the up close surface detail in the photo.

If ur going to rub on that old zinc plated chassis, use a thing that is totally soft, otherwise you will get scratch marks. That's the bottom line. I tried some of these microfiber dish towels, worked great, no scratches (unless you pick something up from the surface).

So, clean the surface carefully first. Alcohol or 409, Mean Green, Fantastic will likely get all the surface stuff off. The Alcohol + Ammonia seemed to work ok, could not say it was better than 409 alone. Might be. Good if you want just a cleaned, dirt free result.

I found that the NEVRDULL really polished well, but has some abrasive action in the wadding. Took the zinc "black" and bamm, gone in short order. Shiny result. Shiny is NOT always a good thing. Probably on things like aluminum IF cans, it could be, or things like that.

The Magic Eraser? Dunno, jury is out. Could not find the proper application for it. It's interesting, slightly abrasive, very slightly. Probably more than any rubbing compound, although maybe on par, but without the cutting action. So, could be a good tool. Might be best on painted surfaces.

But the basic Turtlewax Color Back, which is a basic auto polish with some polishing compound thrown in did the ultimate job IF you want to make the zinc SHINE. The microfiber towel left it shiny without any streak/rub marks.

Paper towel left rub marks. Ick.
The zinc is dead soft after rubbing. Beware.

Fingerprints (inevitably present) from the past do not come away fully with the polishing. And not at all with just the cleaner.

Still may experiment with some chemically active methods...

Turns out the chassis itself is painted! So that it will only require a regular cleaning, maybe a light wax. The IF cans are painted too. No sign the unit was re-done before, so this looks original. Actually this is a relief, less work.

What else?

The black oxide on the zinc sucks...  >:(

Thinking out loud now, it seems to me that the polish on a chassis would be excessive. Really good for mechanical parts though... if they are plated. I found that it may be possible to control the polish when I was experimenting with Color Back. You can find different grades and hardnesses of polishing compounds. The right grade and just the right duration of polishing would give less than a full shine and a clean look. Tricky. The Color Back goes from that to shiny rather quickly. So the thing that would work would in essence be a really really poor polish!  ::)

Ok, a wide shot of the topside from the rear of the radio too...

Next the bit with the Arrf generator and listening on the receiver for the HF Osc.

How much an hour do I pay myself??

   Very Nice...

"Lowest right is the winner.
I did a better job with it on the lowest right, but that was after I took the pic, and you can't see the up close surface detail in the photo. "

I could not quite figure out what worked the best from your post.  Could you clarify what worked best?  I have an SP-200(F270/FRR) & RA74-D PS to restore, eventually.

Thank you.

Jim
Anchorage Alaska

When I get the quad of rotating towers with 1/4 wavelength 75m beams, I intend to work you direct from here to KL7 land!! (yeah right)

I remain semi-comatose while doing all this... trying to do too much without any down time, and squeezing in this project. I did not write what I intended.

After doing all the the upper sections, I did the lowest right with the Color Back car wax and not the microfiber towel.

THEN, I did the lowest left, which is NOT in the picture using the Color Back and the microfiber towel and got almost no evidence of scratches.

In all cases the bottom plate had been cleaned with warm water and dishwashing detergent first.

I'm really not sure that I've found the best system. But if you want pretty shiny, this is sure a good way to go. I'd call it a bright semi-gloss result. The NevRDull comes off as more of a full sheen.

What I'd like is something chemical to "brighten" the zinc. But I'm not sure this can be done without dunking it into a vat and applying juice to it.

I've yet to try any acids or acidic substances. Maybe that's next.
I did do a search on "brightening" zinc and found very little online.
Somewhere I have a copy of Metal Plating Handbook, a yearly publication, from a decade or more back, it may have something on brightening chemically.

Perhaps this is getting "too fine".

Bear, it is most likely obvious to you, but that wonderful Super-Pro 15-Watt hi-fi output is at 600 Ohms.

I've seen more than one ham feed it to an 8-Ohm speaker and wonder where the oomph went....

73DG

At the modest volume I'm running, it woiks FB OM! Good enough for testing.

One possible solution is to take a "70volt" speaker distribution transformer - the one that is hung on the frames of those speakers up in the ceiling, and run that. It works out to be pretty much what you need to do the job. Some of them have multiple taps, I have a few around like that, so you could optimize the taps.

The way to do that without getting too heavy into test gear is to put a scope (best) or a voltmeter on the secondary that is being loaded by an 8 ohm resistor, or the secondar tap that you picked. Of course if ur using a 4 ohm speaker or a 16ohm speaker, use that resistor instead.

Now, put a steady tone on the output (BFO + carrier). When you have the right combination of taps you will see the highest voltage on the load.

Although pretty much anything close will be good enough.

I'd only use high sensitivity speakers with radios like this.
modern Hi-fi speakers not being high sensitivity. Old school speakers like from AM-FM-Phono living room consoles, or PA/SR pro audio speakers are the right sorts. :D

                        _-_-

Tested the HF Osc.

NG except for the working band. Heard in the receiver on the 10-20mc band.

Put the scope probe next to the plate of the Osc tube, nice sinewave. Nothing on the other bands. :(  Now have find out why.

Some possibilities:

Dirty or bent knife switches on the cam switch, or slipped lobe.

Open coils due to bad caps passing B+, and that PSU can really have them over a barrel as in a pinch it can run two of those radios at once.

Soft osc tube.

73DG

Betting on missing the B+... although maybe not.

Unlikely to be a soft tube since the 10-20mc band is higher than the low bands, and it's likely to run lower more than high, I'd expect.

Next time I'll probe the sucker!! C'mere ya b*****d!!

Good thoughts there Dennis! :D

I do have the hammer handy in the drawer, just in case I need it!!  :o

        An ohm meter from pin 8 (cath) of the HFO tube (6J7)
to chassis will check the Band switch. shouls be <2 ohms in
all positions.

        If the tube were soft, one would think since it works on
the 10-20mc band it would still work on the high end of band 4
the 5-10mc.

        You can also Inject the HFO signal into pin 8 of the HFO
socket (V4) and see if the rest of the stuff works..  Easier with
2 signal generators but an antenna should work too.

    RX Frequency + 465kc = Injection frequency.

GL

/Dan

Well not quite, will pin 8 check the bandswitch.

It's trickier than that.
The bandswitch shorts out the unused coils on one side and the CT.
Each coil having three terminals.
When the band is switched IN the grounded CT of the coil is now connected on one side to the cathode, but IT is on ground through the bottom end of the coil.
The first side of the coil, the high side is connected through a cap back up to the grid, which in turn has a cap coupling it to the grid.

The tricky part, and it took me a bit to figure out what to do about it, is that the first side, with the blocking/series resonating cap is also shorted out when the bandswitch is NOT on that band - so all times other than when it is in use, it is shorted to ground.

So, what I just did is to put the probe on the side of the grid blocking cap (which resides above the main tuning variable cap (for those following along) and also checked  the output of the switch that goes to the series resonating cap on the first side of the coil, the other end of the meter on ground.

IF the cap is ok (not shorted) then the resistance measured when the band is switched in will be infinite - cap is good. If there is resistance shown when the band is switched in then there is a short across the cap.

Every band other than the good one shows a dead short!

You could just probe the contacts on the outside of the switch and look at that to ground
as you rotate the band switch too, but that won't tell you if you have continuity back to the grid cap...

So, it's looking like there are dead old micas in the oscillator.

I'll have to figure out how to get into those coils and pull a cap for testing, in the next installment!

I'll post up the section of the schematic in question and shoot some pix of the mechanism that does the switching. Pretty neat switch.

               _-_-

We'll see if it's those caps or not.

Anyhow here is the schematic in question.
The area of interest is the set of coils to the right.
The bottom one is the lowest freq, and the top is the highest.
The trick switch is the thing directly above the coils.
The cap on the main tuning condensor is C15, next to the grid cap on V4, the HF OSC.

If you look at the switch, good idea to zoom it up big on the screen, the horizontal BAR is the bandswitch.
The things that go at a 45 deg angle and look like the usual switch schematic representation, those are the grounding contacts for the unused bands.

When a band is selected a shorting bar comes down and connects across the 2 pairs of contacts. On SW 1E that is shown connected in the second position from the top.

It shows the connection to the ground buss (one buss left and one buss right) open.

In reality it is not a single switch. Not a DPST at all. The way it is made is by using a phenolic guillotine that has silver plated brass wrapped around the bottom of a square piece - this rides up and down. In the down position it engages two pairs of fingers, forming two switches. The ground is accomplished by springy silver plated fingers attached left and right to the switch enclosure.These are NC contacts. (not North Carolina) When the phenolic switch blade rides down, it pushes past the spring contacts and opens the ground connection for the band being engaged. Wheee!

Anyhow pix of this Rube Goldberg operation after I get them off the camera and adjusted for size...

Imagine the conversation in the product development lab at Hammarlund?
"Sven, come here! Look, the design is very good, but we have a problem!"
"Ya vat dis it?"
"Vell, ve will need to short out the unused coils!"
"VOT DO YOU MEAN SHORT OUT THE COILS?? How can vee do dis?"
"Dat is your problem Sven! Make the coils short out!"

Which is probably why this design has these fingers outside the cage to do the grounding of the unused bands. Maybe. You decide!

keep it up, fine , educational, and entertaining!

I have a similar Hammarlund, a SP400 that I started and left off putting back in service.  The beautification effort is commendable but I'm more interested in your electrical restoration effort.  Does the receiver still have the original paper / wax caps in it?  If so, it is a fairly easy job to completely remove the tuning unit from the chassis and do your work on replacing those caps with orange drops.  

While you are at it, inspecting the tuning unit is much easier with it removed.

As we discussed on the air today, I'd be most interested in how you eventually restored the front panel

Al

Al,

Nice signal - as always - emanating through the aether from ur QTH down to the netherlands of the northern Hudson valley in Noo Yawk!

This radio has an engraved (probably stamped in reality) front panel. As mentioned earlier, I had bought a rust-o-bucket some time back and had already stripped the panel (was surprised to see it is nickel plated underneath!) and primed it. I shot it with some metallic car paint, similar to the one in the first post.

What I mentioned in the QSO is that folks seem to often sell parts, including just panels on fleapay...

Patrick, thx.

Anyhow here are some shots of the deep interior.

First one is the place where the greed cap connects back through the requisite blocking cap. (mentioned in the earlier post).

Following that is the shot on the other side of the tuner section showing 'Sven's magic fingers'. These are the shorting contacts of the switch! When the (switch) blade is up the finger, being springy, touches the side of one of the three finger contacts that catch the blades on the bottom of the center of the tuner chassis (under the blades).

Next shot is the top view of that center section showing the cams on the shaft, the blades that go up and down, and you can probably see the silver plated spring fingers on the bottom that contact the bottom of the blades to form the switch itself.

One of the things that always strikes me is that they worked everything BIG back in those days. There is no reason that the same mechanism could not be easily shrunk down to 25% of that size, and work just as well. The coils too, IF and RF, wound on large forms, with big slugs. 20-25yrs later with miniature tubes, later receivers using the same design (essentially) like the SX-88 being the same as the SX-28 to a great extent used smaller cans and coils...  well, big it is...

My next step is to pull some screws from one of the HF osc's coil modules and see what it takes to get it out or get at the cap.

Oh yes, Al, as I mentioned in the first post (I think) this receiver appears to have been worked on by someone - perhaps the NEARFEAST seller - and then never finished because it is/was deaf on all except the 10-20mc band. So, the caps NOT in the tuner unit have been swapped out. I see some resistors that I will likely spot check with an ohm-eater, because past experience has shown that a lot of 60+ year old carbon comps are a wee bit off center value. So, that caps were already swapped.

Also, note the genuine vintage 12kt gold filled Cross pen with RCA logo that was used to point to the blocking cap. You newbies, take note, always use genuine vintage pens to point with when working on vintage gear!  8)

WARNING: do not point with metal pens when voltage is present.

Back to the front panel... I'll be posting some pix of the new front panel after a while. It needs a trip into the oven for a few hours. It's still "outgassing" solvent. If it was summer or even sunny I'd put it in the sun all day. :(  I'll fire up the lab's special junker electric oven this weekend and bake it for a few hours. If the weather holds, I may bake and put another coat of paint, bake more.

But Al, perhaps you can look carefully at the layout, IF the 200 and 400 are the same or close enough you might find a 799/200 panel and repaint it, put the 400 tag on, and ur good to go??

The other option is a virgin aluminum front panel, find an outfit that does CNC engraving (Front Panel Express does exactly this) and have a duplicate made, get it anodized and dump in the color for the labels. If you do a few, you could doubtless sell them and recover your costs.

                     _-_-bear

Pulled one of the HF Osc coil modules.

Pix to come along later...

The cap is fine.
Very very close to spec on my DVM cap checker position.

So, back to looking at the issues. Now I think what is needed is a re-check of the ground or not grounded with the switch theme. Without the module in there, it had better not show a short. But if it does, then either someone has hamboned the wiring or else there is a mechanical problem with the switch.

It never goes simple or fast, does it?

 :o

  I wonder if you pulled the hfo coil from the
working band? Perhaps you could roll a couple into
the same "Slot" so to speak and see if they work
there. A lot of good info can be learned by knowing
what's NOT broke.

   It also appears that the Band spread cap is only
in circuit on the 3 highest bands.

/Dan

Yeah Dan, I played it safe, I pulled the middle coil. No possibility of getting it wrong, since the only working band is the 10-20mc band, and that's not the middle one.

I'm thinking about "Sven's fingers" right now, but some probing about will likely show up the problem. The other thing I noticed is that the CT ground for those coils is achieved through one of the two screws (and a solder lug) holding the coil module in place. So, now I know enough to pull the CT ground and see how things measure WRT the switch operation.

It's going to be something simple, because there's not much else there for it to be.

            _-_-

After checking with Bear, I am uploading the panel of my SP-400.  Note the same flaking off of the paint.  What part of the fabrication process failed in the original manufacture of these panels.

Al

My last post on the ground from the coil module was bass-ackwards, the ground lug goes to the end of the coil, the CT goes to the switch. So with the ground lug lifted the only proper path to ground will be through the switch and "Sven's fingers".

Al, and everyone else, seems fine to come in with related material and things.
I'm re-doing the front panel on this one, so it works in fine.

As far as failure mode, as far as I can tell it's a nickel plated panel, and that may play a role in the paint losing some grip after all this time.

Here's what I said to Al in an email about his panel.
This is only my opinion and what I've done.
By no means the only approach.


I was going to add, IF that panel is aluminum, then you'd probably want to go with one of these newer automotive primers that are "self etching". Permanent grip there. Also, to my eye, yours is actually engraved. The one I have looks stamped. They look different if you know what to look for.

Big palm slap to the head!

DOH!!!  :-\  

Been chasing my tail the whole time. Probably.
Dan, I'm thinking your post about the bandspread was a hint.
Like maybe this was YOUR radio?
Or perhaps this is a well known mod?

So, I'm not so bloody smart then, eh?  ::)
Yeah, right.

Ok so go back to the post with the picture about the wire that was clipped.
Note that there is another wire attached to one of the screws on top of the ceramic
insulator there? That's the top of the bandspread cap. It's attached to the end of
the grid blocking cap C15, and goes to one section of the bandspread cap.

So, what it looks like is that in order to give bandspread to other bands, a wire was run to one
section of the bandspread cap and the wire that normally want to the switch assembly was cut, as it would be shorted to ground on all bands other than the one selected.

Bandspread cap is C2, C2D is this section, there is a wire/clipped wire for each section.

Think maybe the wrong section was picked as this section is small and there is a fatter one... but anyhow that's what it looks like.

I did look suspiciously at the wire immediately, when I opened the radio to look. But what threw me is that this is NOS cloth covered wire,  looks the same as the rest of the wire in the radio.

Now I don't recall if I saw these clipped wires first and "fixed them" or if the radio was still deaf and then I fixed them. Kinda think it was the latter...

Pix to follow... and a "retest" to see if the bands have awakened or not.

YIKES!

GEENUS AT WROK!!  :-X


_-_-


PS. If ur wondering, it worked on 10-20mc. because that was the one band where the grounding "Swen's fingers" were lifted for that particular bandspread section, all other bands had ALL of the grids shorted to ground. Ha ha ha. This is why I get the big money!

It Dont' Come Easy - Ringo Starr

Last update before hitting the hay.

Top two bands and the lowest band, alive.
2.5-5.0mc band and 200khz-400khz, no HF OSC action at all.
Switch contacts ring out ok.
Or so it seems. They don't appear to have a problem with Sven's fingers.
Will double check it tomorrow.
Swapped in a new 630v 1220pf cap in the 2.5mc band, no change.

Not much in the circuit. Must have missed something. :(

  Cool,  Is that a light at the end of this tunnel?

/Dan

No.

Obviously a mud slide into the tunnel, trapping the occupants. Quicksand. The dark and slippery slope.

Btw, watch out, the little variable trimmer caps sticking out of the IF cans?
Electrically hot! Grrrrr... thanks Hammarlund!

As of this moment, there is no good reason that it should not be oscillating on the two dead bands. There are not even any bad reasons. Of course there must be a reason.

You wanna stop over and have a look at it Dan?

                    _-_-

   It's Cool, You have him 60% functional at this point. Much
better than it was. Sounds like it's been Hammy-HamBoned!

    May I suggest just rolling a known good HF Osc assembly
say the 5-10 into the 2.5-5mc slots and see whats up. I would
pull the 100-200 HF Osc coil for inspection as he's the logical
choice for hacking, Maybe someone just clipped all the padding
caps off it.

     I would clearly mark each coil assembly with some sequence
and take a digital photo of it for reference. Maybe there screwed up
now.

     OTOH if you have a "Fancy-Dancy" DMM with a "C" meter
on him, I could Measure the PF's I see on mine from V4 Pin 8
to chassis. Mine has the dust cover on it so I'll need a little time.

     I just got home from work and want to get to church, then
over to KD8FVJ's qth for antenna stringin', Then Beer and Football.

GL and Keep the Faith!

/Dan

A little more headbanging.

THe 200-400kc. band shows HF OSC action when the bandswitch is not quite at the
dentent. Actually, quite a bit off the detent. Soooo... looks like the cover is coming BACK off the top of the mechanism. Could it be a slipped cam? What holds the cams in place? Friction fit??

But the 2.5mc band is still dead. Possibly the same reason, but it does not show any signs of popping to life as the bandswitch is rotated. :(

Since the lowest band works, I'll leave it in peace. Going to pick up a NOS 200-400kc module from W2TRH hopefully later today, and plop that in place of the wayward 2.5kc module, and maybe it will spring to life! But I think this one is going to be mechanical and in the switch, which is not exactly good news.

Otoh, the switch "rings" ok with the ohm-eater, or give the appearance.

Poke, poke, poke. Poke around.

The only way I found to test the series caps is to pull them or pull the module to get them free of other connections and parallel caps.

Took a metal version of the 6K7 HF OSC tube (hope that was the right number, the next tube over is a 6L7, iirc) from the rust-o-bucket chassis and dropped that in. If the numbers have not been scrubbed, the tube type is printed on the upper rim of the octal sockets! Nice, good idea Hammarlund! Bins of them sitting in the factory, one bin per tube type. Made no difference. :(  One can hope.

Will go back to the 12ga. shotgun troubleshooting. But this is looking now like the switch, at least it is on the 400kc band.

I was thinking, change out the 100-200kc band for a 1.0mc-2.0kc and the dial would sort of be ok...

If no one is that interested, I can QRX/QRT.

Any comments or thoughts are appreciated.
I suppose anyone who has done a few of these Hammarlunds is biting their tongues as
I stumble around this one... but I'm not one for stage fright, and don't mind looking a bit foolish.

There are a number of reasons that I decided to document and post, but at the moment they are not so important. The main idea is that this isn't my private monologue and that it's an "open frequency" and we're running break-in. Over?

Im for keeping this thread going from time to time as it could turn out to be a good resource for later time.  I'd put some stuff up but my SP400 is on the rack waiting for some TLC

I am looking for a phenolic strip where I can make up the connection for the cable that goes from the RX to the PS. I'm looking for either hardware or an idea how to make one.

Al

    Yes, keep it going! Problem is that I did the work on mine
20 years ago,   I couldn't recall how I
lashed up the power connections either so I moved him out
a bit this morning to get a PIX for Al.    My other "motivation"
is a CE-100V TX I may pair him up with.

    Al,  I got a chunk of 16 cond. Military cable from something
and just connected the thing to the P.sup with spade lugs
on both ends. The cable is fastened to the back of the RX.
You only need 9 wires from the psup to the rig for operation
but I brought the "SPKR" and "BK IN" lines down as well.(unused)
A "PHONO" input and "PHONES" connection are also available
on the BC-779. I have an ICE-Cube relay hanging off the "BK IN"
terminals.

/Dan

    

Attached is the basic circuit.

In the actual radio it is bandswitched and the values for the coil, shunt and series cap are changed for each band.

Ok, so forget about how the values they have used for a minute. IF one wanted to set up this HF OSC (VFO) for a different band or to cover a different *range* of frequencies, what are the considerations?

For example if you wanted to go for 3.0mc to 7.0mc instead of the 2.5mc to 5mc they have, what would need to be changed, and what controls the high freq side and what controls the low freq end??

The three main components are L23 (the coil) C76 (the shunt cap - air variable) and C81, the series cap. The tuning cap itself (main tuning knob) appears to consist of three physical sections, so whichever band is being used must use some combination of the three sections.

One problem that I see is that each band must more or less tune linearly across the band and go from one end of the main tuning cap to the other in doing this. Then too how arethe trimmers are used to set the band ends?

At the same time one wants the output of the HF OSC to be relatively constant, which means that the "Q" of the tuned circuit needs to stay fairly constant across the range.

For most bands C81 is the same 1220mmf (pf)! What happens if that is changed?
Also C76 remains the same value trimmer for a number of bands.

Of course I get that the coil gets changed to different values, higher L for lower bands.
Does more of the C1D (main tuning cap) cause the freq to go lower or higher? I'm guessing lower, so then the coil is spec'd for the high end of the band??

So, I'm entirely unclear on how the oscillator is set up given what it needs to do.

Insights and explanations appreciated.

                       _-_-

Actual circuit, pdf,  added for reference...

Just because it works on some bands don't assume all the parts associated with the oscillator are good.

Plate voltage OK?  Screen voltage OK?  No leakage in C13 or C15?  Any or all of that could kill the oscillator, and it all depends upon the Q of the L/C circuit whether the oscillator will fire off or not - and I'm betting the Q ain't the same for every oscillator coil.

Yes, you found one of the many hidden hazards of the SuperPro with those hot trimmers.  First radio I recapped was a SP400, i was about 12 and it was one of those hot humid days and I was sweating up a storm.  Grabbed the little screwdriver and held it by the shaft for extra sensitivity and my other hand was clamped firmly on the front panel.  Got the screwdriver on the trimmer and the 300V right across the heart about knocked me out - I was sick for a couple days.  Had I been older I probably wouldn't have survived that.

Whoa, JN! Serious tale there. Glad you made it through ok... nasty stuff.

Yes, the osc is osc'ing ok as far as the tube and the stuff around the tube.

I've worked out the problems as far as getting the bands to work. I think I may post the details of the rest of this romp through Hammer-land (is that where Thor comes from?) via some other means...

...but the short version goes like this; one of the bands, the 200-400kc. band upon closer inspection, and after some actual sleep, looking at it with the brain engaged,  turns out to NOT be the 200-400kc. band any longer! The coils were all rewound! The new range is not quite spot on where it needs to be, but undoubtedly was intended to be 20-30mc, to finish the high end (extending the range of the receiver now to cover 15m and 10mc).

I did find some bad caps in the HF Osc coil modules, and actually replaced one module with a NOS one (acquired by luck locally), which worked perfecto.

There's a whole lot more detail to this, but I'll leave it for now unless someone has other thoughts, questions or comments.

Keep going- I've got two BC779s, a SP-400 and a SP-600 so I'm really into Hammarlunds.  The first BC-779 was badly hacked and took me months to restore it to original.  The SP-400 was almost pristine except that when I fired it up, it had bandspread on the two lowest bands (broadcast), and none on the highest SW bands.  I did a LOT of head scratching over that.  Finally I pulled the cover on the bandspread capacitor, and found four clipped wires... Some prior owner had switched the wiring to the bandspread cap.  Fortunately, it was a simple process to reconnect the wires.
I've spent a lot of time restoring the radios to original (took years to find an original power cable and the knurled nuts for the cover).  So if you need advice I'll keep watching this thread.

Pic of my SP-400 is on radioblvd hammarlund page

Ed  W2EMN

I have a real hack artist BC 779 that plays very well.....It is ugly and the unknown artist removed the push pull audio  and put a power supply in its place....the audio is now single ended and the power supply is on the chassis......Hack and whack job, but I really like the RX and the adjustable bandwidth...Good Luck with yours..

I've got a pre-war 200SX that someone did the miniature tube mods to in the RF section. Fortunately they left the rest alone. Still contemplating converting it back but Johnny convinced me for the time being at least that since the work has been done and it probably works a little better, why bother?


Keep your eyes peeled online if you discover more parts are needed. NOS Super Pro parts turn up quite often on ebay and elsewhere cheap. The gov't procured plenty-o-spares once they got up to speed. The harder things to find end up being knobs, meters, and so on. Even at that, numerous parts sets surface too.

Once it's all dialed in, there's nothing quite like an old Super Pro with shove/yank audio output driving a big old Jensen or EV speaker to fill a room with sound. I'm forever in debt to 'JN and the artist formerly known as the HUZman for steering me back toward the old SPs some years back after I'd dismissed them. One of the finest receivers ever made, can't imagine radio life without one.

Just an update picture.

Working on the dial assembly now - the plastic part with the dial legend is warped. May try heat to "relax" it back to flat, and/or swap out dials from the parts unit. Pix shows unit ready to pull the main tuning module to get access to the dials. The rest of the chassis has been cleaned and you may spot some shined up hardware too... front panel is painted and legend filled in, ready to go.

            _-_-

Bear I think you are spending about as much time authoring this thread as it takes to fix up this radio. ;D ;D

Good read though.  Any of these period higher end receivers are always an experience in frustration and then relief when you have one of those DOH moments when the fix presents itself.  I have a SP400 which I have to get at as the evinrude circuit motored to life.  Fixing these 2 piece receivers with the separate PS is a PITA.  Its like trying to work on a vacuuuum cleaner made of iron. 

So I recently completed a sx42.  Bought it sight unseen.  Turned out to be mostly a basket case.  It sat in may garage weeping every time I drove in.  I finally gave in after 12 years and put it on the bench last winter.  The only good item in the unit was the bandswitch, it being the most important.  The front panel was a disaster.  The chassis I'm  pretty sure hosted some rodent races.  Electrically it showed signs of being worked on by the kid next door in Toy Story (one).  But got it all going despite the roadblocks.  Also TNX to Bill K1BF who dropped off a parts rig with the only nice piece of it being the front panel.  Electrical-wise, the BC band was weakest.  The rest of the bands were OK but not great.  The fix - an IF amp was weak and needed all new components ( I reworked all 3 amps).  So happiness now with the 42.  The sp400 iron vacuum with the evinrude motor is next up.

Peter

Peter, thanks for the kind words. I type fast. :D Learned that when I was doing computer graphics all day, can type almost as fast as I can think it... :D

I think that the SP400 is very similar to the SP200, but as I noted, I am a Hammer-Land newbie. Now I be na expret!

This one is actually almost done. (Famous last words) Just the dials, alignment, and putting the front panel back on, polishing the knobbers. Got some parts set to come via wagon train, so that will but the gilding on this old gal.

Gotta say that the Nev-R-Dull on the toggle switches sure made the bat handles gleam! :D Sweet! Nothing quite so nice and satisfying as good polished nickel plating.

                        _-_-

Working on the tuning & dials now.

Noticed that the follower that makes the detents for the bandswitch (a metal 5 leaf clover made of metal - see the photo) had quite a lot of slop on its little shaft. It did not appear to be as tall as it ought to be for the height of the shaft. The follower wheel was made from phenolic rod. Phenolic rod is actually phenol stuff + paper. Over time it had degraded considerably.

So, I decided to replace it. I selected brass. Brass is hard, but less hard than the steel it runs on. More hard than phenolic though. If I could have put my hands on some 1/2" phenolic rod, which undoubtedly I have some, somewhere, I'd have used phenolic again. It lasted long enough.

Anyhow it takes very little time to think about cleaning up the part, removing the riveted on shaft thingie, drilling a new hole on the lathe, finding the 2-56 screws and nuts plus lockwashers and washer, making the brass piece on the lathe and then installing it so that it actually stays put.

The results below.

It takes no time and effort at all to do a good restoration job. Ask anyone who has done it! :D

Installed.

Don't tighten it just yet....I'm pulling your 40 Mcs tuning unit tomorrow! :D

73DG

No worries, and thank you very very much!

The bottom is still quite accessible. Will be installing an inboard 600:8 ohm xfmr, and still have to try to flatten out the plastic dials... paint the dial escutcheons (how is that pronounced anyhow?) and a few more endless details...

I'm not posting all sorts of detail and less significant work, btw.

                   _-_-bear

Very nice thread Bear.  Thanks

Update.

Almost done with the bulk of the work now. Three months later. Waiting for some stainless steel #3 screws, hardware to replace the rivets on the dials. The reason for this is that the dials were all warped from being stationary for years, and since it is rim drive to the edge of the dials, that makes funky tuning. If urs are free moving, ur in luck!

So I came up with a way to flatten the plastic dials that worked. Dennis W7TFO (did I get ur call right?) send me some additional dials that reflect the now "new" 20mc and up band. BUT, the black sliding band showing thingie (what is that properly called??) does not line up with the legend on the dials, this for two of them - the parts mule I have here and the ones Dennis sent! Some sort of factory thing with the dial printing, since the black aluminum slotted band showing thingies are identical. But this required drilling out the rivets. Finding small rivets of the exact size and length proved not so easy, and there is/was clearance for hardware - very easy if the next part is done as described below, but possible with the black indicator thingie too...

My solution, heretical, is to make an arrangement with LEDs to indicate the band in use with lights. I'll be washing the rear face of the dial with warm white LEDs (those small flat PCB mount types) from left and right for even illumination, then I'm fabricating a series of "straws" to fire a narrow beam of colored light on the center point of the band in use. :D  In order to do the switching/selection of the band, I plan on removing the band changing gears. One gear is on the bandswitch shaft, the other is an idler that is between that gear and the gear on the dial assembly. All are going away, including the rotating aluminum band indicator slotted thingie.

The way it will be made to select the band is via an assembly that hangs over/around the bandswitch holding reed switches. The gear on the bandswitch will be replaced with a brass ferrule + round plastic/pcb disc or arm holding a small Neodymium magnet. Now as the bandswitch is rotated, a single reed switch is activated and the appropriate LED illuminates to indicate the band.

Pix when the whole kit and kabbudle is done... for your viewing pleasure.

                _-_-

ps. the "straws" for the active band indicator lights will be metal, either aluminum or brass, depending on if I want to solder to it and put it together with solder or else with epoxy...

Did a few more things over a period of time...

Sprayed the bezels black after stripping the old paint.

Pix below show removal of the plastic dials, flattening of the out of flat dials, reassembling the dials with the metal hubs, removing the metal center hub on the main dial.

The removal of the hub on the main dial, I'd have preferred to do on my mini lathe, but the lathe and the hub were in different locations, and I did not want to wait. The sharp edge of a very small file works. The hub could be re-swaged on, and/or epoxied in place to refit. I did not refit as I am not going to use the black rotating assembly at all. (see previous posts)

The printing on the dial assembly, as is with the cursor line in the dial window (needs replacement too) appears to be a sandwich of two thin layers of plastic that are adhered together! At least this is how it looks to my eye and with a high power eye loupe. It's clearly not printed on the surface.

The hubs have been reassembled with #3 brass screws, perfect fit! No pix yet.

Also two vintages of hubs are shown below, different swaging, but they are the same in concept.

one more pix...

... this is the dial before flattening. placed between two clean glass sheets in an oven preheated to 170deg F for two hours. Used an IR/laser thermometer to check the temp. Don't think it is hyper critical, and I guessed at the time, it seemed to work. I was worried about melting and/or yellowing. Did not see any.

After it cooled it was almost perfectly flat, but some very slight return to a non-flat state happened, but it's very little. Before treatment it was so non flat that it effected the tuning feel dramatically. Being edge drive and also running through a felt area at the top of the cursor assembly, flatness or lack thereof effects how it rotates. Flat=good!

Did you remove the glass before or after it cooled? Depending how much it warped back, it might be worthwhile to try it again at 200 degrees or so, and give it a long cool down period between the glass sheets w/weight on it.

Beyond that, parts carcasses exist out there as a source for things like the dials, fiducials, etc.

You sure are putting a lot of work into that thing.  :)

Great work Bear and I am sure its a project you will remember for quite some time.  Sometimes its not about the "rareness" of an item, but rather something you just have in your soul to do.

Joe - GMS   

Todd, I let it cool in the oven, under glass... door open.

The problem with the dials  happens when they are "parked" in one position AND the alignment between the dial disc and the dial window (plus felt) which is a slot through which it travels is not dead perfectly even, then the disc takes a warp. Over time, of course. If you keep tuning it, then it all evens out. So the carcass dials I have and got all had the same problem to some extent. I did the heat treatment on the two I chose to use.  

May try the higher temp on one of the others, just to see. But the result is quite acceptable as it is. You can see the wavy part, but it is slight.

Joe, yeah this has turned into a project, but the elapsed time is mostly due to having to deal with other matters out in the "real world". :(  This all happened because I bought a DOA chassis which was lurking under a table at a NEARFEST, cheap! Then I decided, what the heck, I'll strip the panel and put lipstick on the pig! You can see what happened after that... hope I have this eye candy unit back together soon so you FB OM can gaze upon it! (in case you don't recall the early posts, this is not the rusty pig from the hamfest, but parts have been borrowed here and there - not many though)

Big.

Heavy.

2 chassis.

Complex.

Those are the neat things about the SP-10 thru the 400.

The best thing is the audio quality.

It trumps all the era comm RX, and most of the more recent.

73DG

Absolutely, D. Beats all the other receivers I have in the audio dept (especially driving the right speaker) and does pretty well in other areas for a mid-late 30s design. The big trick as the manual states, is to leave the beasty on to stabilize. The WWII/post-WWII modification Hammarlund put out helps greatly. Ralph/W3GL posted it on here a few years back.

I've got what I think is a complete-minus S-meter and power cable BC-779 with cabinet and supply that needs to find a new place to collect dust, once I get it dug out of my station. Best of all - no hacks that I can see! Still has all the octal tubes, no extra holes, etc etc.

These are the dials in final assembly.
Loctite applied with the tip of the dental probe. #3 screws, brass.
They will get sliced flush with an abrasive cut off wheel and a Dremel tool. (has
that become like "Kleenex" and other brand names that have become generic?)

I suspect that IF you reassembled the main dial with the black rotary part that shows the band in use, that
might require the screw heads to be filed or pan head screws to be used. But I am not re-installing it.

                  _-_-