The AM Forum

Since there was a good chance my "I Got an Offer I Couldn't Refuse"  topic was going to stray  from QSO related topics, into technical stuff, I've decided to continue it here.  As I mentioned in my original thread, I'd post photos.  Here they are.  As you can tell from the front panel, it has had some mods done to it.  It also has a power cord with the ground installed on it.  BTW would anybody happen to know the part number for the mic plug that will mate with my mic jack?




73,
Ellen - AF9J

You should be able to tack solder the plate leads on the 807 caps.
The head radiator caps really don't sink much heat off the plate since tie connection is a very thin wire, unlike a 4-1000A. A stock V2 had little clips like you would see in a TV set.

Hard to see the mic connector in the fotos Ellen. Is it a 2 or 4 pinner?

Right of the bat, loose the screen regulator.
I'll check the junkbox for plate caps.

Hi Buddly,

The mic plug I need, is a 2 pin male with shield.  In other words, it's like the style of plug my Cheyenne had.  If they eran't available anymore, I'll do what Rodger, WQ9E suggested, and replace the present jack on the Viker, with a 1/4" stereo, like my Swan had.  Thanks for the offer of a plate, but that's OK.  Rodger is sending one to me in the mail.

73,
Ellen - AF9J   

looks like a "2" holer..........  try rat shack ...........  klc

RF Parts has the correct plate cap connectors (ceramic), and they are quite inexpensive.

Grant/NQ5T

Ellen,

The plate cap and a 22 ohm resistor went out in the mail this morning, hopefully it will be there by Saturday given the holiday delays.  I had a matching pair of nice looking plastic encased plate caps from a Valiant I was planning to send you, they have the resistors built in and sealed in plastic.  Of course one of the resistors was open and they are a pain to cut open and repair so I sent a regular cap like the ones used in my Viking 2.

73, Rodger WQ9E

Thanks Roger! :)

Ellen - AF9J

As I recall the original Vike II mic connection was the old Amphenol 2501, so be advised there is no need to stay with the 2 pin style.

(http://www.rapco.com/catalog2/images/connectors/tn2501.gif)


Whoops, didn't read that. OK, never mind. I bet the two-pin mic jack is there because the rig has been modded with T/R switching.

2 pin was used in the V2 CDC.

...u can use "plumbers tape" for the plate caps, till ya get others...looks cleaner inside than my viker...
  ellen..do u have a vfo fer it?   tim...sk...

Yes I do Tim,

I'm going to use my Heahkit VF-1 with it.

Ellen - AF9J

Hi Ellen and all,

I don't know if the numbers have changed but when the rig was new that mic connector was the Amphenol MCF-2 so the plug would be the MCM-2. The stock items are MCF-1 and MCM-1 respectively.

Happiness is a big... Viking.

Thanks for the info guys. :)  BTW per Jim's, W5JO's suggestion, I checked behind the back of the front panel.  The BNCs are not hooked up.  Jim thinks that the BNCs and the two holes over the meter, may have been from mods (that were undone) for MARS use.  I'm going to try (desparately) to see if I can get it going for this weekend, since it sounds like many of us are going to be on-the air, with the extended Turkey Day weekend.  I may just go with a 1/4" stereo jack for the mic. Oh, I forgot to mention, not only have the rectifiers been solid stated, but it also has a 3-prong grounded AC plug installed.

73,
Ellen - AF9J

...ellen..ya never know, those bnc connectors might be for a scope pick-up, or headfone monitor.  both ideas are here on the web page some where...maybe it was for a digital readout, on a freq counter. you certainly could use them for any of these things...gud luk, and i will be listening 3700-3735kc...tim...sk...

Ellen, the part you need is an Amphenol 80MC2M 2-pin mic connector.

They are made now by WPI. Available at any large parts house. All Electronics has them too.

I can send you one gratis, as I have many.

Well, I got the plate cap I needed (thanks Rodger!).  I cleaned out the Viking II big time.  It sure was dusty!  I also took off the bottom cover (are they sure 18 screws are enough? ;) ), and cleaned under the chassis. Oh, I forgot to mention that I also took off the tubes and vacuumed the tube sockets, and sprayed DeOxit on the switches (moving them through their ranges).

I noticed when I looked under the chassis, that a couple of mods were made.  the two, 30W, 30 ohm resistors had cut leads.  Is this one of th audio mods I briefly read about?  Also, a couple of leads were cut from the 15 mFd capacitor, near the power cord.  Since the cord has been grounded, I wonder if that's why they were cut.  I couldn't seen any evidence of a relay, so I'm not so sure the PTT mod has been done.  I've included some photos for your perusal.  At the present time, I have the filaments powered up, so I can try to reform to some extent, the few remaining paper capacitors that are in it.

73,
Ellen - AF9J   

In your picture of the 2 white sand block resistors, there is a relay right next to the 160m in/out shaft. The other 2 pictures are a bit too fuzzy to tell what is going on when you blow them up. I guess you'll have to look at the skizmatic and find out what has been done. Looks like Hammy Hambone has struck again!! all in all the V-2 is a pretty simple tx to troubleshoot. There isnt all that much to them.
                                                                       The Slab Bacon

You need 2 poles to switch AC to the HV transformer and the other to close the Key line. The V2 CDC put a set of contacts across the key jack and the other across the HV AC front panel switch. the CDC put 2 diodes across the bias winding to make about 100 volts DC. A small low voltage transformer could be mounted to operate at other voltages. Then a relay is required to switch the antenna between the TX and RX.

Well, I powered up the filaments for a few hours to burn things in since the Viking II sat for so long. So far so good.  Sugar, my little Tortie cat sure liked the heat from the tubes!  I had to put a towel on top of it to keep her and Sarah away from any HV stuff.  After I did that, Sugar curled up on top of the Vike II while it was powered up, and conked out for a long nap.  I realized a little while ago, that even though I don't have the mic plug yet (and at this time I'm feeling too lazy to rip out the old one ;) ), I could still power it up on CW, to run more checks.  Also, in all likelihood, keying it up on CW, would activate any PTT relay in the radio. I'll do that later on. Since the radio sat unused for years,  I've powered up the filaments again for a few more hours.  Here's a photo of Sugar basking in the Viking II's warmth.

73,
Ellen - AF9J

Ellen,

Be very sure to check the status of the caps that filter the LV supply!

On the Viker II that I had, they were shorted, and did not blow the fuse, and did not cause overheating immediately - it just smoked the LV transformer after I left it on for a few hours and walked away. (yeah, sure, everything is ok.)

On rebuild I put a fuse in the ground side of the *secondary* of the LV supply to make certain that that supply would not be frying the iron ever again. You might want to take the expedient of putting a fuse holder in there. I was able to mount one in the existing hole next to the transformer itself.

BTW, use the flash on ur digital camera to shoot those pix, and put the camera on "flower" (closeup) mode as well....

           _-_-bear

Nooooo, nooooo, nooooo....

Photo 2: those are not relay coils. That's the AC input filter! be careful there. The caps that go across it ought to be evident, unless they're on the reverse side. I replaced mine with 1kv film caps, the old ceramics are likely toasty at this point.

The cut filter cap is exactly what I was talking about in the previous post!!
Ur. gonna have to replace all the wax/paper caps in the rig.

Good source? Those ubiquitous computer monitors that people are chucking out all over the place! They usually have small value film caps with good voltage ratings and a set of electrolytics rated at >400vdc...

Oh, do NOT run the rig with anything on top of it - it is shy on cooling as is.

            _-_-bear

The resistors with "cut leads"?

Are they cut or is that two resistors in series??

That's the speech amp section.

Btw, there is also a wax cap that needs replacment hiding just under that large oil (8mfd) grey cap shown to the LR in that same image...

BAMA - a link from the banner menu here in amfone.net has the complete manual and schematic.

And, for everyone taking jpegs of equipment here, always use the closeup setting (the flower icon thing), and throw as much evenly dispersed light at it as you can (artificial or natural or both) and THEN set the flash option so that the flash is NOT on AUTO, and will flash (the lightning bolt icon) - then you'll get a bright, clear, shadow free image!  ;D

Bear,  My camera is a cheapo pinhole type digital that I'm not sure has the "close-in function". I'll check  The two 30 ohm, 30W ceramic resisitors each have one lead cut.  They are wired in parallel. So, in effect they are floating.  Almost all of the old paper capacitors have been removed BTW.

73,
Ellen - AF9J

Cats like to "claim" radio gear. Dunno why. Maybe they think it is an elaborate heating pad built just for them.

Wouldn't cover it with a towel while powered up though. This was the era when rigs didn't have cooling fans. Top cover perforations and rear louvers were theoretically intended to dissipate heat.

Ellen, maximize the light in that case! Soak it in light!! Too much you can't have!
Use outside light and artificial light or any combination you can manage.

Warp Factor 9 lighting!

If you have software like photoshop you can take the final image and adjust the brightness and contrast. Then use the sharpen filter, then reduce the image size down to ~800 pixels wide for something that really needs detail or 640wide for regular posts, reapply the sharpen filter save as jpeg, pick a medium quality save.

30 ohm, eh? Sure it's not 30kohm? But what do the connected ends connect to? That will tell you something about where it is in the circuit.

The filter cap with the lead cut off, needs attention... btw. Unless you did that already.

You'll want to change some things in the speech amp after you get it mostly settled and mostly operational...

                   _-_-bear

              _-_-

Hi Everybody,

Sorry this took so long, but here's what's been going on with the Viker II:

1.  Further examination revealed that my Viking II dos have the PTT mod.

2  I had absoloutly no Plate Current at all.  Circuit checks showed no voltage from the SS rectifiers.  These were replaced with a single SS rectifier that was beefy enough to handle the current load (thanks Rodger!).

3.  With the new SS rectifier in,  Plate Current was way too high (over 420 mA, even with the crystal switch setting in a position where there was no crystal).  This indicated a several possibilities: not enough bias voltage, a bad set of finals; or a bad clamper tube. 

4.  The bias was checked on both the finals (with and without the finals in [a major difference in bais voltage with finals out could indicate the finals are bad) and the modulator tubes.  In both cases (with and without the finals in) the bias was too low.  There was no significant change in the readings, with the finals removed  So the finals weren't the problem.  Bias voltages as measured on the finals - I only got about -55V (it should be at least -75V).  On the modulator tubes - I only got about -21V (it should be -30V).  So it looked like the bias capacitors C12 & C13 (that goofy dual 15 mFd paper capacitor), were bad.  I replaced the dual paper biasing capacitor with 2, 200V rated 22 mFd.  Biases on the finals and mudulator tubes were rechecked.  This time I got -77V on the finals, and -28V on the modulator tubes.  Much better.

5.  The Plate Current was rechecked.  It's still way too high (on the order of 390 mA).  Since biasing has been eliminated as an issue with regards to the high plate current, it looks like the 6AQ5 clamper tube is bad.  I ordered 2, 6AQ5s this morning (since the buffer tube is also a 6AQ5, I figured I might as well also replace it at this time).  Until the 6AQ5s arrive, I can't do much more with my Viking II.

6.  I also ordered some other capacitors from Mouser to replace the remaining paper capacitors in my Viking II. 

73,
Ellen - AF9J 

sounds like the bias voltage is low. the modulators should be around -35 volts. Heck I converted to AB2 and run 29 volts. AB1 the plate mod current will be quite high having high voltage on the mod screens. Check the filter caps on the bias.
Better yet yank the tube and install a couple 1N4007s to solid state it.
You can down load the manual on bama.
You might remove the tubes and see if it comes back to normal. I think the output of the rectifier should  be about -90 volts.

> Since biasing has been eliminated as an issue with regards to the high plate current, it looks like the 6AQ5 clamper tube is bad.

Not sure about the V2 specifically, but I wouldn't think the clamp tube would come into play unless there was no drive.  I wonder if the crystal or vfo frequency may be doubling or tuned to a harmonic in some stage that is far removed from the final tank frequency.  If you have a frequency counter, you could check and if it's way off, you could probe back through the driver/buffer/etc to see where the problem starts.

73',
Kent/KX5KW

a clamper tube pulls the screen down a bad tube will not push it up. yank it out the rig will run fine without it. A shorted tube could mess with the bias again yank it if it is a suspect.
First before the rig is keyed does it have final grid current. If it does not then find out why before you key the final. You should be able to easily get 10 ma on 75 meters.
No grid drive check the drive pot. Put the function switch in CW and tune up the osc and driver for max final grid current then reduce it to around 8 ma with the final un keyed. Make sure your driver stages function properly before turning on the final or modulators.

Ellen,

Try dipping the plate??

Without the plate being dipped, the current will be VERY high.

On my Viker II the thing pins the meter before it gets dipped!

Surprised the heck out of me! I thought I had a shorted tube!
Take the plate cap OFF one tube or two tubes for testing, if you want to keep the plate meter inside its range. I removed one (check for B+ first), it stayed inside the range, did not pin.

Put the rig into "grid" meter, put the switch for vfo to "zero" and peak the "exciter" knob for max. Then set the drive control for 8ma. That' something between 5 and 10, nothing too fine. Next, set the AUX Coupling control down to the first or second click  from full CCW position. (Assuming a dummy load here) Put the meter into plate, turn the switch on and key it. Dip the plate by swinging the FINAL control. If you don't see much dip, key off, and change the AUX Coupling control, try, repeat until you find a range that gives some dip. I think you'll get dip pretty quick. The variable control "fine" can be varied key down for optimizing the loading you want. I load to about 230ma max.

Sounds to me like the rig is working...  ;D

             _-_-bear

Here';s a little more info people (I wrote my last post at work, so it was a little hurried):

1.  I have been unable to dip the finals (which is frustrating for somebody who's done the peak and dip routine for 25 plus years).
2.  I did replace the bias capacitors.  After replacement - the biase voltages were: -77V for the 6146 finals and -33V for the 807 modulator tubes.
3.  My grid current is very low (less than 1 mA).
4.  My excessive plate current even occurs, when no crystal (or VFO) is in the oscillator circuit.
5.  All readings were done in CW mode, and keydown had no effect on them.

BTW - I'm finding the Viking II manual I downloaded from BAMA, to be much better than the manual I have for my Scout.

73,
Ellen - AF9J

On the rig's meter? In the Grid mode?
Should peak up, as I wrote in the previous post.
To use the VFO, place the function switch into "Zero" - then peak the grid current.

Oh - the position of the "kicker" arm below the chassis seems to often be changed and set wrong - that will cause the rig to run very funny and not be on 80m when you dial it up. On the Viker Duece I got, it was wrong, and it took me about 3-4 hours to figure out that the VFO was ok, it was just being switched wrong!! I had to undo the set screws on the kicker and reset it to the proper position.

Try 40m, if 80m and 160 do not work... the kicker arm is usually not a factor on 40m!


Makes sense... no dip... try the trick I mentioned above first, remove one or two plate caps and see what the plate meter does when you can see it not being pinned.

Sounds like you have a drive problem - no grid current on the meter = no drive?



Ok, but is there B+ being applied on the plates of the finals when it is keyed?
Keydown = apply B+

In the CW position, the xtals will fire, and you can peak the grid using the exciter control and set the grid drive mA using the front panel control... using the VFO you have to dump it into the "zero" position to see grid excitation...

You ought to be able to hear your xtals fire in the CW position on your receiver, no keydown!


_-_-WBearGCR

HI Bear,

I can't get much grid current at all, when I try to peak it per the Viking II manual.  BTW, my B+ to the oscillator is 285V.  I'm a bit leery about testing the B+ on the finals, until I get the Plate Current to come down.  I don't want to nuke the finals.  To clarify things, following the tuneup procedure, with just the filaments on, I get little to no grid current, when I try to peak grid current.  When I flip on the HV, Plate Current is extremely high, and I cannot get it to dip down to where it belongs.    Plate current is also extremely high, even when I have the cryastal slector in a postion, where i have no crystal plugged in.  BTW, I can get decent drive/buffer current.  I will check the kicker arm.  Maybe it is funky.

73,
Ellen - AF9J

Just a quick heads up concerning an earlier post I read, I would NOT recommend removing the plate connectors on the final on any rig using tetrode or pentode finals unless you also pull the screen voltage feed-otherwise you are probably going to damage the final tube since the screen current draw will be excessive when there is no plate voltage. 

Rodger WQ9E

DO NOT WASTE YOUR TIME KEYING THE FINALS UNTIL YOU FIX THE GRID DRIVE PROBLEM. GRID DRIVE HOLDS THE FINAL IN CLASS C. LOW GRID DRIVE WITHOUT A FUNCTIONAL CLAMP NUKES THE 6146s

My V2-CDC mod of the day. Put a 3 conductor line cord on the rig. I found a nice shielded cord from an old monitor headed to the scrap heap. Added the 5R4 heater winding in series with the LV transformer primary dropping the heater voltage from 6.7 to 6.4 volts with the unit cold. Should drop a bit as the transformer heats up. Result cooler LV transformer and better heater voltage on all the tubes.

let me help with one part.

Put a 3 conductor line cord on the rig.

Every transformer run rig you have needs a 3 wire AC power mains ground and a earth ground. And you need to make sure there's very little difference between the two grounds. Paranoid? you bet, and you should be too.



 

YUPPER caps to chassis from the line put voltage on the chassis. Every time I connected the antenna there was a spark. Did mine yesterday. Also filed the hole to accept a nice strai relief for the new cord.

Hi Guys,

I'm luck in one regards - the 3 conductor mains cord is already installed on the Viking II.  I'll do some more checking of things today. 

I just got done finding out that my Scout has a power supply problem.  The 6146 voltages are almost 200V over what they're supposed to be.  Voltages from the 5U4 rectifier are off by as much as 140V!  The worst part about it, is that I put in a new rectifier tube when I got it, due to the old one being smashed up in shipping (the guy I bought ti from, only packed the Scout in a single walled box with a few crumpled up newspapers in it, ugh!). Now I'm not sure if the Russian 5U4G is junk, or if I have a bad power transformer in it (the transformer's mounting tabs are bent, so it leans a little bit to one side - in other words it may have suffered shipping damage too).  So much for easy fixes!  The thing worked fine for the first two months I had it.

73,
Ellen - AF9J

Awright - pull one of the 6146s, that will put the plate current within the range of the plate meter when it is way out of resonance.

I pulled the plate cap on mine, and the 6146 did not fry... but then again I keyed it fairly quickly and dropped it quickly too...  ::)
(and I have a small box of 'em to fry...)  ;)

Ok, do you have a scope Ellen?
That will help with troubleshooting the oscillator/buffer/drive circus...

Once you get the clowns out of there, and the elephants in line, it should fly straight!? :o

Doesn't that pot on the front panel that does the drive level fry?
Isn't that the "Chernobyl pot"??
maybe that's the problem...?

                 _-_-bear

Hi Bear,

Yes I have a scope (I got it for free from the same neighbor who gave me the ICOM IC-740).  As for the front panel Drive pot, I'm able to adjust it down to the level the manual suggests for buffer current.  Buffer current tune up seems to go OK.  Things go bad, when I get to Grid Current (basically zip, as read in the Grid Current meter function), and Plate Current (almost 400 mA, as read in the Plate Current meter function).  Tonight I'm trying to work some of the heavy metal stations.  I got the Scout working again (everything pointed to power supply issues, and it turned out that the Chinese 6146W I put in was junk; I put in another 6146W, and it works fine <sigh!>).  I have a long weekend, so I'll get to the Viking tomorrow.

73,
Ellen - AF9J

Well why not fire up that scope and see what is going on at the driver tuning cap. If you have a signal there check the 6146 grids

Today's V2 CDC modification.
Connect the LV rectifier heater winding in series with the LV transformer primary and 5R4 heater winding. This dropped the filament voltage to around 6.1 volts.
The temperature rise of the transformer dropped to just barely warm after an hour of operation. So with the 5R4 winding I got down to just under 6.4 from 6.7 and now with all three in series just under 6.3. The voltage is still in spec and everything functions fine. Slightly lower heater voltage should be good for tube life.
I noticed the only wire left on the 6AL5 socket was the green 6.3 volt heater lead. I cut it and fed it back up the harness to the terminal strip at the VFO power socket. Then I removed the socket and installed a second fuse holder so I could fuse the LV transformer. It sits right next to the final RF plate choke so really can't put any parts there.
 

Tim's WA1HLR's modification of compensating for the Old Design of 115 VAC Mains now run on 120 VAC, where we use an unused 5 V filament winding to buck the Low Voltage, bias, filament transformer primary is Excellent.

This works well in many older receivers and transmitters lowering especially higher than normal filament and bulb voltage extending their life!

I initially did this along with protecting the primary's with a 1 picosecond Transorb and slow MOV http://hamelectronics.com/k1deu/pages/ham/general/pages/surge_suppression.htm . But now prefer a different method. This method is strongly condemned by Many who believe in Constant, Stiff voltages for all things. For example in my DX-100 I added a 20 Ohm 20 Watt resistor in series with the LV, bias and Filament transformer primary. Yes my Filament voltage is now within range using 120 Volt Mains and when I snap the power switch on my Dial and meter light bulbs and filaments in the tubes flicker on gently instead of an initial bright flash on. Yes this mod requires much more time to locate a spot above the chassis to mount the Big resistor (or small in a receiver) with some Teflon wire but my dial lights and tubes are much happier. 73  John K1DEU 

This weekend I cleaned up the JS around the LV transformer primary with a little terminal strip in place of the TVI filter. I found a nice shielded line cord off an old monitor and installed it with a nice strain relief.

Then I looked at the low voltage output sitting at 340 volts. We were talking about the drive pot on 75 today and Tim suggested changing to choke input on the LV supply would reduce the dissipation in the pot and make the transformer even cooler.
A quick cycle of power and a moving of a filter cap wire dropped the voltage to 250 volts. I had to raise the pot setting from 2 to 4 to get back to the right final grid current. 6AQ5 audio driver current dropped to about just under 30 ma from 40. Still had plenty of monkey swing to the 807s. The rig stayed on all day and at 6:00 the transformer core would barely warm a finger. Now that I only need 1 cap in the LV supply the LV tube socket area looks like a good spot to mount a 680 uf / 500 V beer can.
The negative lead of the drive pot goes to the bottom of the chassis. The pot dissipation could be reduced even more if a resistor is added in series with it.
I looked at the plate voltage at the 807s plate caps I have plenty of drive to swing them quite close to zero volts.....guess they are healthy.