Hello All,
This set has become a real nightmare. Someone in the forum sent me a very legible wiring diagram. I checked my work and found that I forgot to replace a single capacitor. I replaced it and the radio is exactly the same. I can hear microphonic sounds if I tap the detector/preamp tube. A transistor radio tells me that it's oscillator is very much alive too.
The radio worked beautifully for about 10 seconds in total. Now there appears to be no connection between the tuner audio output and the pre-amp input, or something else has gone wrong.
I hear clicks, hums, and silence through the speaker. One time there was a blue glow (Gas?) in one of the 47s for an instant. But it no longer does that.
Maybe a resistor is open? This is a total nightmare set. Everything I check is ok, yet it "refuses" to work. But something isn't ok. But what?
Please help if you can.

Thanks,

Dave

If you have not made basic voltage checks. There is a voltage chart. Most problems are found this way. Open coils are a real possibly given its age, ca. 1932. T2 that drives the power amp or the RF plate coil L4 among others for such a vintage radio.

Richard

:
:If you have not made basic voltage checks. There is a voltage chart. Most problems are found this way. Open coils are a real possibly given its age, ca. 1932. T2 that drives the power amp or the RF plate coil L4 among others for such a vintage radio.
:
:Richard
:
Sounds like it may be something intermittent or shorting. I would also check around the 'blue glow' tube. It might be indication of a problem / overload there.

Did you retest that tube after it occurred? Maybe it failed, either becaue of another issue, or just picked a bad time to die...

Think of it this way...you must be close if it worked for ~10s... ;-)

::
::If you have not made basic voltage checks. There is a voltage chart. Most problems are found this way. Open coils are a real possibly given its age, ca. 1932. T2 that drives the power amp or the RF plate coil L4 among others for such a vintage radio.
::
::Richard
::
:Sounds like it may be something intermittent or shorting. I would also check around the 'blue glow' tube. It might be indication of a problem / overload there.
:
:Did you retest that tube after it occurred? Maybe it failed, either becaue of another issue, or just picked a bad time to die...
:
:Think of it this way...you must be close if it worked for ~10s... ;-)
:
Could also be related to the missing cap causing some other component to fail...

Hello All,
I have checked and double checked the coils and all is well with them.
From terminal 2 on the magnetic cartridge connector to the chassis, I measure 89 ohms. This makes no sense whatsoever. The coil between the grid of the detector/pre-amp tube, does not connect in any way to the chassis. Or does it. Back to opening the can again and again to make sure that no part of the leads are touching the chassis. I replaced the wires so this can't happen. So I will check again. I need to hear the hum hum as I touch that second terminal on the magnetic cartridge connector. Once I hear that I'll know that all is well.
I measure 300 volts in all the places where it's supposed to be 230. I measure 50 volts right where it should be on tube 1. Other measurements are good. It passes the transistor radio test, which picks up the oscillator,which is also working perfectly.
So this has to be the problem. Inside the IF transformer can, something is connecting that grid coil to the chassis, and allowing me to measure 89 ohms (According to the schematic, it's really 93 ohms but that's close enough).
The power amp is working, as I've said all along. There is no way I'd hear microphonic sounds(through the speaker) from the pre-amp tube, if the amplifier wasn't working.
Second IF transformer will be disected again and again until that secondary doesn't connect to the chassis. No part of that transformer should connect to the chassis in anyway whatsoever.
I should only see the 1 Meg ohm when the link on the magnetic cartridge terminal is in place connecting terminal 2 to terminal 1. That's it. When the 89 ohms is gone from terminal 2, all should be working well.
More reports later on the RCA R-7A Nightmare Set.

Thanks,

Dave
:::
:::If you have not made basic voltage checks. There is a voltage chart. Most problems are found this way. Open coils are a real possibly given its age, ca. 1932. T2 that drives the power amp or the RF plate coil L4 among others for such a vintage radio.
:::
:::Richard
:::
::Sounds like it may be something intermittent or shorting. I would also check around the 'blue glow' tube. It might be indication of a problem / overload there.
::
::Did you retest that tube after it occurred? Maybe it failed, either becaue of another issue, or just picked a bad time to die...
::
::Think of it this way...you must be close if it worked for ~10s... ;-)
::
:Could also be related to the missing cap causing some other component to fail...
:

I see what you mean by the resistance reading from terminal 2 of the phonograph input. have you removed the 2nd detector tube to make this reading? Or take a reading from the grid to chassis? (trace in reverse)

Warren,
I replaced the wire from the second IF transformer and now when the link is disconnected I hear the hum hum when I touch terminal 2. This is more proof that the audio amplifier is working perfectly!! But when I re-attach the link between the first and second terminal, no more hum hum and no sound from the tuner. I have tried several number 27 tubes for both oscillator and detector. I am pretty sure they're all good tubes. The oscillator is running as witnessed by the transistor radio. I did hear the tuner working before. So what's happened I can't understand. But I'll find it.
I was measuring the 91 ohms from the secondary of the second IF transformer because one of the leads was touching the chassis. I have replaced the wire. Now that works. But why there's no sound from the tuner, I have no idea. Maybe it will "decide" to work again. Maybe I have bad leads on the first IF transformer too that have to be replaced.
More reports later about the "Nightmare" set.

Thanks,

Dave
:I see what you mean by the resistance reading from terminal 2 of the phonograph input. have you removed the 2nd detector tube to make this reading? Or take a reading from the grid to chassis? (trace in reverse)
:

Hello Again Warren, All,
R8 was disconnected. I have no idea who disconnected R8 from the cathode of the detector tube, so it was OFF. Then they had B+ connected to the cathode. But I cut that wire before even trying out the radio. Also the 150 ohm resistor is missing from the volume control. The radio is playing. The nightmare is over.
That link must be dirty because I have to use a clip lead to connect terminal 1 to terminal 2 even when the link is firmly tightened. Weird.

All the wires to both IF transformers were touching the chassis. R8 was disconnected from the cathode of the detector tube. The signal overloads the tuner but it has no AVC in these sets. So the 150 ohm resistor will probably help. I just shortened the antenna. That helped.

I am still borrowing this speaker from a r-7, which is un-restored. So I either need one for it, because I'll probably restore it too.

Thanks to everyone,

Dave

:I see what you mean by the resistance reading from terminal 2 of the phonograph input. have you removed the 2nd detector tube to make this reading? Or take a reading from the grid to chassis? (trace in reverse)
: