[Radioroslyn]

Even now when I touch the center tab of the volume control, the radio picks up one station, faintly, no matter where the dial is set. Is it possible the tuning condenser is bad? 

Nah that's a red herring. Do you have a strong local AM station?? I suspect that the osc is running else it wouldn't have negative voltage on the 1fs grid of the mixer tube. You can verify it by listening for it an other receiver. set your PT-95 dial at 100 (1MC) Use a shirt pocket radio tuned to 1450KC Hold it near the 7A8 tube. tune around 1450 and if it is working you will hear a loud dead spot. That is the osc running.The tuning condenser is bad? Pretty rare sometimes plates get bent don't think so but that's about it.
Terry

[dseverson]

This might be a clue. The previous owner had added a resistor between pins 6 and 8 of 35Z3 that I removed because it isn't listed on the schematics. I put back an 11k resistor because I didn't remember whst wss there previously and now I get one local station loud and clear. How does this figure?

[Nick3092]

Pin 6 is not connected on a 35z3. So it's being used as a tie point and you'd need to tell us what else is connected there.

[dseverson]

Besides the resistor on pin 6 of 35Z3, one wire is connected from pin 6 to I think pin 5 of the osillator transformer, another wires goes to pin 4 on 50L6, and a third wire goes to pin 3 of 35Z3. On that pin 3 is a 510k resistor that is connected to pin 4 of the same tube 35Z3.

[Radioroslyn]

Well I don't think whether you have a jumper or a resistor there matters much. Fact is you have HV on the pin 3 of the 7A8 and you have -3v on the control grid of the osc. These two voltages tell that the that it is running. If the coil was bad you either would not have HV on pin3 or you would not have any feedback and the control grid would measure +.
As mentioned before take a listen for in another receiver.
Terry

[dseverson]

I finally got around to getting a transistor pocket radio. I tuned the PT-95 to what I think is 100 (1mc) and the transistor to around 1450 and held it near the 7A8 tube. I hear a loud buzzing/popping noise. Is that the oscillator working?

When I say I think I tuned the PT-95 to 100, I can't be sure because the tracking is way off. A station on 560 in my area comes in around 810. To rewind the antenna loop, I used thicker gauge wire than than the original but the same number of turns. Would that cause the tracking to be off?

[Radioroslyn]

I finally got around to getting a transistor pocket radio. I tuned the PT-95 to what I think is 100 (1mc) and the transistor to around 1450 and held it near the 7A8 tube. I hear a loud buzzing/popping noise. Is that the oscillator working?

Yup that is it.


When I say I think I tuned the PT-95 to 100, I can't be sure because the tracking is way off. A station on 560 in my area comes in around 810. To rewind the antenna loop, I used thicker gauge wire than than the original but the same number of turns. Would that cause the tracking to be off?


Generally speaking No. It won't cause the station to be in the wrong place. It will cause poor sensitivity.
So is your pointer at 55 (550) kc with the tuning condenser all the way closed? If so I would try adjusting the osc trimmer to see if you can move things down a bit. You shuold try to find a station up near the high end of the dial as that is where the trimmer will have the most effect.
Terry

[dseverson]

Well, I think I will have to call this radio a partial success. It picks up three stations at the low end of the dial but at the upper end, I hear the oscillator popping through the speaker. I get nothing above about 640. Adjusting the oscillator and antenna trimmers don't help anything. Adjusting the 1st and 2nd IF transformers don't do anything to help either, however, the oscillator popping speeds up or slows down depending on how much I adjust them. I'm certain the radio needs to be aligned but without a signal generator, it's a lost cause.

Couple quick questions about mica caps. How important are they and, by looking at the schematic, is there a way to tell what pins the 250mmf mica is conttected to on the 50L6GT? http://www.nostalgiaair.org/pagesbymodel...014176.pdf

Thanks for all your help.

[Eliot Ness]

.......Couple quick questions about mica caps.  How important are they and, by looking at the schematic, is there a way to tell what pins the 250mmf mica is conttected to on the 50L6GT?  http://www.nostalgiaair.org/pagesbymodel...014176.pdf

They can be pretty important, but I don't think the 250 at the 50L6 is your problem.  But to answer your question you'd refer to a tube chart to figure out the pin #'s:

http://www.mif.pg.gda.pl/homepages/frank...25L6GT.pdf

In this case it is between pin 8 (cathode) and pin 5 (grid 1).

A tube manual is pretty handy to have around, but here is an RCA manual that is a free download:

http://bitsavers.trailing-edge.com/pdf/r..._Jul63.pdf

[dseverson]

This is great information on tubes. Thanks for sending it.