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Philco 42-340 - Printable Version

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Philco 42-340 - Jimradio - 09-29-2021

I have this restored, but believe I have an oscillation issue. I'll turn on the radio, I can here some noise coming from the speaker no stations. I take my meter to check voltage on the plate of the XXL, the stations pop right in as soon as I touch it. It will stay playing for a very long time. After the radio cools off it will not start again unless I check the voltage on pin 2 the plate. I don't have any other XXL's to try, may have to order a few.

What else could be the problem.

RE: Philco 42-340 - mikethedruid - 09-29-2021

First thing I'd do is reheat all the solder joints to that tube socket, and maybe to anything directly connected to the tube socket on their other end. If that didn't solve the problem I'd reheat all the solder joints at the ends of the tube pins, and see if that solves the problem. It sounds like an intermittent connection to me.

RE: Philco 42-340 - Jimradio - 09-29-2021

Ya, thanks Mike sounds like a good idea.

RE: Philco 42-340 - Jimradio - 09-30-2021

I swapped the two XXL's that are in the radio and now it seems to work I will keep checking it.

RE: Philco 42-340 - Radioroslyn - 10-01-2021

If the XXL that is in the osc position is weak this can cause the set to be inoperable. But when swapped with an ok XXL in the mixer position it could restore the set to an operating state. Sensitivity going to be lousy. XXL aka 7A4

GL

RE: Philco 42-340 - Jimradio - 10-01-2021

Thanks terry, I need to order some XXL/7A4's just do not have any spares.

RE: Philco 42-340 - Jimradio - 10-04-2021

Now have two new (nos) XXL/7A4 works great.

Thanks guys for your help.

RE: Philco 42-340 - Jimradio - 10-06-2021

Mike was right, I did a lot of soldering (reheat). Still it did not fix it, one time when it would not osc. I got out my halogen work bench lamp turned it on and the radio came alive? The next time I touched my meter to the + of one of the Ecaps and it came to life. Took all wire's off the terminal and reapplied them and changed a resistor. It has now turned on fully three times in a row. I will do further testing.
Tubes were not the problem like I had thought.
Thanks Mike

RE: Philco 42-340 - MrFixr55 - 10-07-2021

Sounds like that thing is the son of the Model 89 that I am working on. Did the 77 update, better but not good. Rewinding the Osc Coil tickler part deux. Converted the band switch to a radio / aux input sw, just in case. Sounds pretty good with Old Time Radio from the internet piped in.

Best Regards,

MrFixr

RE: Philco 42-340 - MrFixr55 - 10-07-2021

Seems like a lot of mica caps in the Osc circuit. Maybe consider replacing them if not already done, maybe starting with 26 on the Ryder's Schematic, a 100PF from Osc grid to ground. If that leaks or shorts, that's all she wrote for the Osc.

RE: Philco 42-340 - Jimradio - 10-07-2021

It failed again, I did replace the 100pf on the XXLs, didn't help. I don't have any 250pf which some of them are. Could I go higher on those. May have to order some.

RE: Philco 42-340 - Jimradio - 10-14-2021

Finely found the problem. On the OCS XXL/7A4 pin two(plate) replaced the 33K resistor and the 250pf cap. it has been working since this procedure was preformed.

Thanks for the help.