37-630 Possible Silver Migration Problem - Printable Version
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37-630 Possible Silver Migration Problem - glwells - 06-30-2011
I just completed the rebuild of a 37-630 console and it works great with one exception. I am getting the typical silver migration noise intermittently. I have been dealing with differences from the Run 2 diagrams from the docs on Nostalgia Air's site and the version I have. I worked thru it even though the alignment of the compensators are laid out differently (less of them). Still figuring out which is which in the RF and Ant sections.
The version I have does not have caps 38 and 42 visible (110pf) as an example.
My question is are there caps inside the IF cans that I am somehow missing from the schematic I have? If so, what are those values that probably need replacing? If not, any thoughts on another direction?
Thanks for everyone's help.
Gary Wells
WB9AYD
Re: 37-630 Possible Silver Migration Problem - codefox1 - 07-01-2011
Did you mean Model 37-640? Can't seem to find that one on Nostalgia or Breitman. Most of the time the micas are inside the can, and sometimes even another couple of components can be found hiding there. If it's just the two screws that need to be removed to get inside, then it's not that bad . Don't even bother measuring them if you take the can apart, just replace them, use fresh stock, they go bad whether you use them or not. You need not ask how I learned this. I always replace any resistors I find inside, and use heat shrink tubing or replacement wire if the leads are shabby.
Re: 37-630 Possible Silver Migration Problem - Chuck Schwark - 07-01-2011
Yes, there is a 37-630. Very similar to the 37-620, and it has a Shadow Meter.
Micas can go bad. Refresh them with new dipped silver-mica types.
Chuck
Re: 37-630 Possible Silver Migration Problem - glwells - 07-01-2011
Thanks for the responses. It is a 37-630. I suspected that there were micas in there even though they don't show up on the schematic. Now I have to figure out what value to use.
Gary
Re: 37-630 Possible Silver Migration Problem - codefox1 - 07-01-2011
Oh, are these possibly the horrible 110 PF capacitors molded into the can next to the coils that I've heard about but not seen? I'd stop right here, and see if your moderator Chuck Schwark has his usual top of the line schematics, etc... at a very modest price.
Can't remember where I read a thread on this topic, but fixing this varies somewhat in pain between a stubbed toe and root canal, and I think it might be toward the higher end.
Re: 37-630 Possible Silver Migration Problem - glwells - 07-01-2011
Well that would answer the question of where the heck those two 110pf caps and a 51k resistor are hiding. I have looked everywhere for those as the drawings for Run 2 shows them coming off of a terminal strip on the side but they were mysteriously missing from my project. I'll wait to hear whether the root canal is a more fun approach or not from Chuck before I attempt surgery.
Gary
Re: 37-630 Possible Silver Migration Problem - Texasrocker - 07-01-2011
Once you do a dozen or so of these special heart operations, its really not all that bad. Just time consuming and having a few beers handy for steady nerves
and a good magnifier lamp helps with the surgery as well. Do the cardio cath bypass while your in there also... ( new color coded wire leads back out of the transformers). 
Re: 37-630 Possible Silver Migration Problem - codefox1 - 07-01-2011
Well they always give the real nasty surgery to the old guy, even on television. It's radio or it's not. Scalpel?
Re: 37-630 Possible Silver Migration Problem - Texasrocker - 07-01-2011
Yep, you guessed it Codefox, I suppose Im considered a old fart these days (hee hee). I certainly don't claim to be Dr. Kildare of the I.F. trauma unit, but it certainly isn't my first rodeo with these type surgeries. After the surgery is over, I kinda get this warm fuzzy feeling inside once the patients snap, crackle, and pop is gone. These particular patients have nice "cans" too!! Pass the scalpel, tweezers,small snips, new silver mica cap, resistor, and new color coded wire leads please. And keep the soldering iron ready we are about done. The dressing under chassis will be done by keeping the new color coded cath leads as close to orig as possible and put them back in the same positions. Now the fun part, lets have a beer Codefox! Something tells me this isn't your first Rodeo either!!
Re: 37-630 Possible Silver Migration Problem - codefox1 - 07-01-2011
T'aint. I have a few grinding wheels of different grit, and a professonal grade dental lab drill (like a dremil but ball bearings, too bad I can no longer see well enough to make this an advantage.) Grind but do not crack, if crack, crazy glue and wait. and solder quick and sure. Sure don't be wanting to show the green unless it is a certain day in the spring. Prayer also helps. Whomever disigned this, I hope they did not have children.
Re: 37-630 Possible Silver Migration Problem - Chuck Schwark - 07-02-2011
Those 110pf caps in the bakelite block are NOT mica! They are typical rolled foil-paper.
That's why they leak just like all the other tubular wax-paper caps.
Replace with dipped silver-mica types.
Chuck
Re: 37-630 Possible Silver Migration Problem - codefox1 - 07-02-2011
Agree for sure. Fresh Silver Micas are in order. Somebody had a thread on this not long ago, just can't put my finger on it.
Re: 37-630 Possible Silver Migration Problem - Texasrocker - 07-04-2011
I have flown by the seat of my pants over enough years in replacing bakelight philco condensers in many of their various year models sets of radios that nothing surprises me in that buried in tar and tie points philco condensers jungle. What a "dealer scam" that was from the getgo to get folks to purchase "original" parts!! I use Riders schematics and can most usually evaluate the needed replacement parts in most old radios from either the philco pages in Riders, or other brands that used the same type circuitry in same year models. I can see where the Philco condenser book AES sells would be beneficial to newbies in this hobby. So far, Taint never been one philco bakelight block I haven't figgered out yet going by either philco, or other mfgrs similar schematics that used similar circuits, with or without the philco condenser code numbers book. And replacing the old rubber grommets on the RF deck after I remove it can be done by cutting and fitting small hard black rubber vintage style faucet washers avail for cheap at Lowes, HD, or hardware stores. They will last a lot longer than gum rubber type replacements. Best of luck with your restorations!