You are welcome - sounds like you know what you are doing
I am still without a variac. Actually I thought we had one here - but no idea where it is or whether I am dreaming. Anyway, you are ahead of me. I do use a dim bulb tester, the name refers to the equipment, and not its operator
Hey Ron, that wasn't me that used those codes, that was the person I was quoting.
I knew a Frank Ramirez who was the Pastor at Elkhart Valley Church of the Brethren, in Elkhart, Indiana from 1990-2003 and he looks just like you (from what I can see of you in your profile picture) are you related by any chance?
And OK, I didn't know that the person you were referring to was a person who lived in recent history and not the 19th Century Hymn Writer.
And I'm trying to be nice, I was just mentioning that I have a few radios that I have found that are still working with their original electrolytic cans in the radio's circuit yet.
Do you have any ideas as to why this radio might be having issues with not wanting to receive signals?
Troubleshooting your radio, here are my thoughts (some of which may have been covered in earlier posts):
You say it receives no AM or FM stations. First thing to check is whether the audio stages are working - inject signal at the volume control. Anything from the speaker, hum, crackle, hiss? It was mentioned before to check windings on speaker, field coil transformer etc.
If not, back to basics. Are all the valves (tubes) seeing heater power and HT? From what I understand, if it is a series heater string set, if one heater is open, the set stops working. Easy enough to check the filament on each tube for continuity. If that is not the cause, establish whether there is B+
Currently I don't have a signal generator but I will be getting one this afternoon hopefully.
I tested all of the tubes and all of them test good yet (I did have to replace the 19T8 because it tested no emissions on a all of the sections), the tubes are working and so is the speaker because I do hear a slight hum and hiss out of the speaker but just no audio, and no stations.
That's about as far as I've gotten with troubleshooting on this radio.
(This post was last modified: 04-15-2020, 11:48 AM by captainclock1988.)
Try touching the center terminal of the volume control with a screwdriver. If you hear a hum then you know the audio circuits will produce sound. When the signal generator arrives you can start with the 455 kc radio signal sections as if you are doing an alignment. All you need to do right now is identify the point where the signal is lost.
If you don't hear a hum then you can start with an audio signal to the grid of the 50L6 tube and work back to the grid of the 12SQ7 triode.
This radio uses all miniature tubes, it uses a 50B5 as the output tube, a 35W4 as the rectifier tube a 19T8 as the AVC/Detector/A.F. tube, 6BJ6 tube as the Ratio Detector Driver, 12BA6 as the IF Tube the 12AT7 as the Oscillator/Converter tube.
hope this helps.
And yes when I get the signal generator this afternoon I will definitely be trying to use that to check the radio.
OK. You can find tube pinouts on line, or trace the heater wiring. Continuity checks are easy and will settle the heater condition quickly. For example:
OK so I think I figured out whats wrong with this Radio, the output transformer primary is open from what I can see with my multimeter, the output transformer's primary is supposed to measure 200 Ohms but its measuring open.
I'm not sure how the output transformer's primary would of went open but it did somehow.
Which I'm not sure if I would be able to find an output transformer that has a 200 Ohm primary and a 0.8 Ohm Secondary, that has a centertapped primary.
0.8 ohm secondary is not important, the turns ratio is to a degree.
You need to match 2.5kOhm to3 Ohm, that is your turn ratio is 29 (30 is ok or close).
The tap ..... without knowing the position of the tap (it is likely not a centertap) we don't know the exact feedback gain.
However I think you might be able to do without it.
Or some resistive divider AC blocked through capacitor feedback could be fashioned.
A Hammond xfmr, 125SE, almost any size, like 125ASE, will do.
Black and Yellow is close enough for your speaker and the tube.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 04-18-2020, 12:28 PM by morzh.)
Unless the Play Things of the Past reopens very soon, and they have yours or similar xfmr in stock, using regular untapped one would allow for the radio to start playing and then you could experiment with the feedback.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Here's the schematic for this radio, as you can see on the schematic, this Radio's Output Transformer's Primary is indeed center-tapped, because the output transformer's primary measurements are taken between the two outer leads and the inner lead doesn't have measurements to it, meaning its center-tapped.
The speaker on this radio is a permanent magnet type speaker with a 3 Ohm Voice Coil that has one side grounded to the chassis through the housing of the speaker, the ouput transformer has a 200 Ohm center-tapped primary and a 0.6 Ohm secondary that has one side grounded to the chassis through the transformer's housing, that's what the schematic says anyways.
