37-630 recap of RF subchassis - Printable Version
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37-630 recap of RF subchassis - Guest - 10-07-2005
Hello Ron and all!
I just got this 37-630 on the bench for a recap. I see cap 14 (.05uF,) is well hidden, and that it goes from B+ (just downstream of the shadow meter) to chassis ground. Now, to change that cap... I will run out to the hardware store and look for the smallest wire cutter available, perhaps I can cut the cap lead at the bandswitch. Then, hook-splice a new cap in place. Okay, what if that's not possible? Could I leave the old cap in place with the ground lead fastened to a small terminal strip to insulate it, and install the new cap externally to the RF subchassis? Or, add a .47uF in series to ground? I really don't want to have to pull the bandswitch on this one. The other 3 paper caps in the RF subchassis all look serviceable, thank heaven. Thanks for all replies in advance! And thank you Ron, for starting the Phorum!
- Chuck Schwark - 10-07-2005
This Service Tip may help??
PHILCO SERVICE HINTS & TIPS - NUMBER 2
Philco 1937 Sub-chassis Servicing Tips
- Ron Ramirez - 10-07-2005
On the larger Philcos such as your 37-630 and bigger, Philco stuck a couple .05 uF caps in between bandswitch sections. It's a pain, but the easiest way I have found to service these is to (groan) remove and disassemble the RF sub-chassis so that you may more easily reach those "hidden" caps.
Personally, I think David Grimes, the inventor of Philco's "Unit Construction," should be punished by being forced to actually service a dozen or so of his RF decks.
- Jerry Huelsbeck - 10-09-2005
Ditto on Ron's suggestion. Sometimes its easier to go the long route, than try to struggle with the extra-extra longnose pliers. Just make detailed drawings, and label each wire as you unsolder it, and its not that bad. Better to to this kind of job right the first time, rather than have to go back in there for that cap that was just too hard to get to. While everythings out you can replace the gum rubber washers, resistors etc also. I bought some gum rubber sheets from McMaster Carr (sp?) and custom make what I need. Heres a shot of the 38-116x chassis before and after..... Kinda scary when you have it all apart, but when its done and playin great, it was worth it. (as you can see I went a little crazy and replaced the leads on the transformer as well. This set also had an open filter choke and open audio interstage transformer) The filter choke in the picture is a Hammond replacement, painted black with the outer paper layer of the original Philco choke glued on - hides it a little..... I have yet to find an original interstage transformer, so I did the R/C coupling, and it sounds great. Hope to find a replacement someday though.....
[Image: http://i9.photobucket.com/albums/a77/1philco/9c5b4000.jpg]
[Image: http://i9.photobucket.com/albums/a77/1philco/8bfc183f.jpg]
- 49Stude63 - 10-10-2005
Ron are you saying David Grimes should have been put in prison, given the wrong tools to work with, and have to repair 37-116's and 38-116's all day long while trying to maintain his distance from his big cellmate named Bubba??? Just wondering.
- Chuck Schwark - 10-10-2005
Actually, I think that would be too good for him.
- Jerry Huelsbeck - 10-10-2005
Did any sets share the same RF deck, or did they all have different decks? If a few models shared the same deck then it might make some sense production wise ?
- Chuck Schwark - 10-10-2005
A few 37-6xx have the same deck/socket physical arrangement, but components are slightly different, like the 37-620/630/640 etc.
- Ron Ramirez - 10-10-2005
I know early versions of Models 37-620, 37-630 & 37-640 share the same RF deck. Ditto Models 37-116, 37-690 and, I believe, 37-675 (with automatic tuning).
In 1938: 38-116 Code 125 and 38-690.
This is far from a comprehensive list; there are some more that shared RF decks, and there are several with RF units unique to that model only.
- Guest - 10-13-2005
Hi guys,
I managed to get the wire clipped where the hardest cap to change was connected to the bandswitch. But I couldn't fit a soldering iron in to reach the little hook I formed on the end of the wire. However, I accidentally slid some of the insulation on the other wire connected to that same point on the switch, leaving a soldering-iron-reachable solder point for the new cap. The set just got done with its recap and sounds great, works on all three bands. I found an open 20 K resistor in the voltage divider to the RF/converter/IF screens; replacing it gave me ten times the sound from the set. Still, the shadow meter doesn't open up much with no signal; something's still giving me low plate current. Guess I'll check the rest of the resistors and tubes, verify operating voltages. and this should be resolved without too much trouble...