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Help with Philco model K-852 - Printable Version

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Help with Philco model K-852 - canerods - 08-19-2008

This is my first post, I'm hoping you can help. I want to give this radio to my daughter-in-law, but I hate to tell her it needs to warm up for 10 minutes before you can hear anything!! When it powers up, even on local AM stations, the audio is distorted and impossible to understand. After about 10 minutes, it gets much better. I've replaced all capacitors, including the electrolytics and I've checked all the tubes (all seem good) and even swapped out the 50C5 with another one. I've reheated the tube solder joints to be sure they were good. I don't know where to look next?

I know there's a Sams Photofact: 604-10 available, does anyone here know where I can get a copy?

It's a model K-852. Printed circuit board with tube sockets, 5 tubes: 50C5, 35W4, 12BE6, 12AV7, 12BA6.

Here's a photo, sorry it's blurry! [Image: http://i181.photobucket.com/albums/x304/vortigerncrancocc/philco.jpg]

- rghines1 - 08-20-2008

Try justradios.com or samswebsite.com for a Sams schematic. The Schematic Bank at http://techpreservation.dyndns.org/ has Beitmans in djvu format for free download on your radio.

The garbled sound could be the antenna is not connected properly. Verify the antenna wiring. Schematic shows one end of the antenna goes to the ganged tuning capacitor not the B- bus or the chassis. The other antenna lead goes to pin 7 of the 12BE6 tube.

Confused about the 10 warm up unless you have a really weak tube somewhere. Systematic troubleshooting is called for.

Richard

- canerods - 08-20-2008

Richard, thanks for the helpful information. That Schematic Bank is a cool place -- great tip!

I'll check the antenna. It should be OK since it's part of the cabinet back and connects thru a interlock.

I was thinking a weak tube also... they check OK on an emissions tester -- I may have to substitute tubes to be certain.

thanks again,
Joe

10 minuite warmup - DCASAZZA - 08-20-2008

I too would suspect a s l o w tube. Most checker don't do a great testing like the use and load the reciever presents.
I know this is a line operated reciever, but if you touch the center lug of the volume control with the test lead of a volt meter, with the negative lead of the meter not touching anything, you should hear a hum. If it's loud and clean sounding you have an IF / RF concern. (You just eliminated half the circuits one way or the other. Do it safely and don,t touch anything but the insulated test probe with your skin.