mr_fixer
08-08-2017, 08:15 PM
Hey All!. I got this today and after some tube socket cleaning it works mostly.
This is the table radio in the Danish Moderne case. mostly works but has almost no high freq audio response. this has the small square electrostatic tweeter and no audio comes out of it.anyone have a schematic or know of what to look for to fix this?
Check the power supply to the tweeter. Often it's nothing more than a few failed electrolytics that need replacing.
teevee
08-12-2017, 05:54 PM
If you have DC voltage across the tweeter, it should (if the coupling cap is OK) work. If not, there are a few threads on the interwebs dealing with the Grundig/Saba/Emud/etc. German radios that use electrostatic tweeters, and how to revitalize them. I've had about 70% success rate rebuilding them.
mr_fixer
08-13-2017, 09:18 PM
If you have DC voltage across the tweeter, it should (if the coupling cap is OK) work. If not, there are a few threads on the interwebs dealing with the Grundig/Saba/Emud/etc. German radios that use electrostatic tweeters, and how to revitalize them. I've had about 70% success rate rebuilding them.
I have B+ going to the tweeter through a resistor and there is a tap from the audio output tube going to the same side of the tweeter through a small value ceramic cap .005 mf the return side of the tweeter is only a .01 ceramic to ground which i would think would block the dc. so it kinda does have voltage yet it doesn't depending on the way you think about it. It doesn't look tampered with.
Titan1a
08-14-2017, 12:06 AM
My equivalent Zenith K735 had a bad tweeter which I had replaced with a piezo tweeter. High frequencies are back.
teevee
08-18-2017, 12:16 PM
I have B+ going to the tweeter through a resistor and there is a tap from the audio output tube going to the same side of the tweeter through a small value ceramic cap .005 mf the return side of the tweeter is only a .01 ceramic to ground which i would think would block the dc. so it kinda does have voltage yet it doesn't depending on the way you think about it. It doesn't look tampered with.
Curious, what does the schematic show? All the electrostatics I've worked on had a DC bias on them.. the return is usually to groune.