I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?

Jon, can you point us to a schematic for this?

I'm a little confused from your question, though. Is it an IF xfmr or the oscillator coil that was open?

A bad IF xfmr shouldn't keep the oscillator from working, should it? And a bad oscillator coil I don't could be bypassed with an RC ckt like can be tried for an IF xfmr.

:I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?

hi been there done that i finally bought a nos coil from playthings of the the past and the set works good now i think i could have rewound the original coil but in mine it was fried and fell into pieces and there was no way to count the winds. this set is kind of shakey anyhow as the vol. works by limiting ant. signal.butch

Thanx Butch. I've got two of these things in real nice cabinets and it would be a shame not to get the radios to work. I can't find that site. I spelled it playthingsofthepast.com and it brings me to www2.links.com some kind of shopping guide. I'm curious, does that coil assembly have to be perfect for it to work (majic)?

:Thanx Butch. I've got two of these things in real nice cabinets and it would be a shame not to get the radios to work. I can't find that site. I spelled it playthingsofthepast.com and it brings me to www2.links.com some kind of shopping guide. I'm curious, does that coil assembly have to be perfect for it to work (majic)?

This is the web address of Playthings of the Past:
http://www.oldradioparts.com

Dennis Wess

::Thanx Butch. I've got two of these things in real nice cabinets and it would be a shame not to get the radios to work. I can't find that site. I spelled it playthingsofthepast.com and it brings me to www2.links.com some kind of shopping guide. I'm curious, does that coil assembly have to be perfect for it to work (majic)?
:
:This is the web address of Playthings of the Past:
:http://www.oldradioparts.com
:
:Dennis Wess

i think it has to be very close to work i tried some substitutions on mine they work somewhat but not really very good but if you can count your coils winds and get them in the same positions as original i see no reason why you can't rewind one unless the radio gods are out to get you.butch

:I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?

::I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?

:I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?
Jon, Check the cathode bypass network on the IF stages. If the values are off you will not get required gain. Your oscillator coil could have probems. Inject a signal into the mixer stage at the frequency necessary for the oscillator to provide the proper IF freq. Then you can tell if the IF transformers are both good. If they are good on the center frequency of the disired IF, then you have a tracking problem in the mixer circuit. Check the trimmer capacitor on the oscillator section of the variable cap. You could also have a problem with the detector circuit. Inject a signal directly into the diode plates of the detector and see if you have enough audio gain. Would help if I had circuit but notice nostalgia doesn't list that model. Good Luck, Boyd

:I'm restoring a Grigsby-Grunow 15A for a friend. The primary of the 1st IF was open. I painstakingly rewound it! Got the oscilator to work only on one end of the dial. As you tune, the amplitude fades to nothing. I bought another one from the internet to make comparisons, but it too had the same coil open. This time I did the R-C bypass teqnique. Same symptom. I have been able to get a tone from an RF signal generator to get through to the audio stage by peak alignment, but not enough sensitivity to get a station. Anybody been here before?

Jon, It is me again. If you haven't-go to the resources part of this sight and download the manual for the model 15. This is a screen grid receiver and they are very difficult to align because of the low IF freq being 175 kc, they have imense image problems. Grunow even cautions one about not aligning the if cans. Also the cathode bias is controlled by the volume control. Check the resistance of the pot and the series resistor that comes from the volume control. Also this receiver has an ascillator tracking condensor. You need to rock the tuning cap to get it set up correctly on the low end of the band. Again the impedence of your rewinding effort is very important as the method in which you align this set. Good luck again, Boyd