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no reception 57C - kbm37-630 - 11-12-2011

Hello,

Yesterday picked up a 1933 57C at a local auction..$15 Bucks .It had a new, but period ac cord, when I got home sure enough it had already been recapped ( Need to check for correctness ), tubes are correct. Turns on , but gets virtually no reception, very faint hum and occasional static chirp when volume control is turned back and forth.

Where should I start and what should be my first checks ? I have the schematics and parts layout, are there any points where I can check for correct voltages, etc, there are none shown on the schematic.

Kurt/ Newbie now hooked.

Re: no reception 57C - Ron Ramirez - 11-13-2011

Kurt's 57C, photo furnished by Kurt.

[Image: http://i326.photobucket.com/albums/k420/mrphilco/ARF/Pictures_00002.jpg]

Re: no reception 57C - Ron Ramirez - 11-13-2011

I'm thinking it could be a coil problem - either the antenna or oscillator coil, or both, have gone bad. Common ailment in 1928-1936 Philco sets. If the set has been recapped and if going through it reveals that all connections were made properly according to the schematic, then the coils would be the next thing to look at - assuming, of course, that the tubes are good.

You got a bargain on that 57C. These, and the lookalike 54C, usually sell for $60-80 and up on eBay. I don't know what the appeal is, but people seem to really like these little sets. I recently acquired an empty 57C cabinet; I have a poor 57C chassis with no power transformer, missing a tube socket, and missing its original speaker. Now the challenge is to acquire these parts and try to turn this parts chassis back into a working chassis.

Re: no reception 57C - kbm37-630 - 11-13-2011

Ron,

Thanks

I checked the caps and all looks fine, all resistors are original ( Might be a good idea to replace them ? ). Unfortunately I don't have a tube tester, as I said before they all glow. Is there a basic check I can make without a tester ? Wish the hardware store I remember as a child was still around, they all had testers..... Icon_sad

Since I'm new at this, how can I check the oscillator and antenna coil ?

Kurt

Re: no reception 57C - Radioroslyn - 11-14-2011

To measure the ant coil, Unplug set connect ohm meter from the ant post and chassis ground. Turn the volume full up. Meter should read just a few ohms if not time to rewind.
The oscillator coil can be checked by connecting the ohm meter to chassis ground and then find pin 5 of the mixer tube. Pin 5 will have a resistor and a capacitor in parallel connected to it. The other end of the r/c will connect to the oscillator coil. At that point connect your ohm meter. Same as the ant coil, must have a low resistance like 3-5ohms.
Terry

ps Check 21, 22, and 24. Those are the critical ones they need to be within 10 percent of spec. Check 9 and 11. Those should be within a Kohms of spec.

Re: no reception 57C - kbm37-630 - 11-19-2011

Thanks,

Found antenna coil is bad ! Is there anyone that rewinds them ? Or is it something I can do, if so how ?

Also found two resisters to be substantially OOT. Question is how to determine if they are 1/2 W, 1 W etc. They are # 24 240K ( meas. 443K ) and #9 20K (meas. 18K).


Kurt

Re: no reception 57C - gvel - 11-20-2011

Based on the circuits the resistors are in, I'm guessing 1/4 watt resistors should be fine, but get 1/2 watt instead, just because they look better, and the price difference is miniscule. Hopefully, others will confirm my guess!

Just for grins, connect the lead of your antenna wire, to the grid cap of the first detector/oscillator tube (77). The radio may function, is this fashion. By all means - replace the antenna coil, though.

AES has a suitable replacement, new, antenna coil.

http://tubesandmore.com/

The part number is: P-C70-A

Re: no reception 57C - Radioroslyn - 11-20-2011

Hi Kurt,
Sorry I didn't get back to your PM. As gvel mentioned if all else is good the set will play with a bad ant coil just connect the ant to the grid cap of the mixer tube. I think I would rewind the original rather than replace it with a universal replacement which isn't designed for that set.
To rewind remove coil from set. At the bottom you will see a narrow winding this is the primary which is open. Remove this winding only! Do not remove the other winding ( the larger one) The primary isn't critical about 20 turns of 32-38ga wire. Direction is not very critical.

#9 Is close enough to work fine, replace #24. 24 should be a 1/2 job as most of the resistors are, The exceptions being the two voltage divider resistors and the wire wound resistor at the center tap of the power transformer.

Definitely should recap this set before trying to get in to work. It will save you a bunch of time and trouble just to find that all the caps are in need of replacement anyway.

Terry

Re: no reception 57C - kbm37-630 - 11-20-2011

Hello Greg and Terry,

Thanks for your input.

For old resistor wattage found the answer on the Philcorepairbench site, you can determine the proper wattage based on the size, see attached site.

http://www.philcorepairbench.com/resistcompare.htm

Definitely will rewind the primary instead of replacing the coil.

Terry, The set was already recapped when I found it, I verified that It was done correctly.

Will let you know results asap..

Kurt

Re: no reception 57C - Radioroslyn - 11-21-2011

Well I think I would start poking around with my volt meter and see if it has HV where it need to be.
Terry