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Author Topic: BC-799/SP-200 Hammarlund Recondition/Mod Project  (Read 39834 times)
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WBear2GCR
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« Reply #50 on: December 30, 2014, 04:30:27 PM »

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! Cheesy



* CAM-FOLLOWER-ORIGINAL.jpg (318.94 KB, 1480x1110 - viewed 528 times.)

* CAM-FOLLOWER-SHAFT.jpg (362.87 KB, 1480x1110 - viewed 482 times.)

* CAM-FOLLOWER-REPLACEMENT.jpg (300.99 KB, 1480x1110 - viewed 515 times.)
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WBear2GCR
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« Reply #51 on: December 30, 2014, 04:31:12 PM »

Installed.


* CAM-FOLLOWER-ASSEMBLY.jpg (274.14 KB, 1480x1110 - viewed 493 times.)
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W7TFO
WTF-OVER in 7 land Dennis
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« Reply #52 on: December 30, 2014, 08:26:51 PM »

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

73DG
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WBear2GCR
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« Reply #53 on: December 30, 2014, 09:59:32 PM »

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
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w1vtp
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« Reply #54 on: December 30, 2014, 10:49:52 PM »

Very nice thread Bear.  Thanks
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WBear2GCR
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« Reply #55 on: April 02, 2015, 09:25:53 PM »

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. Cheesy  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.

                _-_-
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WBear2GCR
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« Reply #56 on: April 02, 2015, 10:02:19 PM »


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...
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WBear2GCR
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« Reply #57 on: May 03, 2015, 07:04:45 PM »

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.



* HAMMARLUND-DIAL-DRILL-RIVET.jpg (427.8 KB, 1480x1110 - viewed 485 times.)

* HAMMARLUND--DIAL-HUB-REMOVA.jpg (237.51 KB, 1480x1110 - viewed 444 times.)

* HAMMARLUND-MAIN-DIAL-HUB-RE.jpg (268.63 KB, 1480x1110 - viewed 431 times.)
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WBear2GCR
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« Reply #58 on: May 03, 2015, 07:13:58 PM »

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!



* HAMMARLUND-DIAL-BAKING.jpg (429.24 KB, 1480x1110 - viewed 512 times.)
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Todd, KA1KAQ
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« Reply #59 on: May 06, 2015, 01:59:50 PM »

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.  Smiley
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« Reply #60 on: May 06, 2015, 02:12:34 PM »

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   
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Simplicity is the Elegance of Design---W3GMS
WBear2GCR
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« Reply #61 on: May 06, 2015, 03:23:07 PM »

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". Sad  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)
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« Reply #62 on: May 06, 2015, 04:37:37 PM »

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
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« Reply #63 on: May 07, 2015, 10:15:03 AM »

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.
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WBear2GCR
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« Reply #64 on: May 13, 2015, 12:31:28 PM »

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.

                  _-_-


* HAMMARLUND-DIAL-HUB-SCREWS.jpg (275 KB, 1480x1110 - viewed 499 times.)
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