grundig: 3028 USA; Grundig Majestic lost volume control after recap

I just finshed re-capping my Grundig 3028 and now I have no volume control, just one steady volume, tone is flat also

As I am a novice, could someone please advise me as to where I probably made the mistake on replacing which capacitor?

The replacement values are all good, I think I just hooked one of them up to the wong place

 

Does anyone have pictures of the under chassis with nice close ups of the capacitors so I could compare? That would help alot

I did put an ohm meter on the volume pot and it does show change so I am pretty sure the pot is fine

This radio played ok except for a hum before I did the full re-cap, so I am sure its something I did

Good news, the hum is gone

From now on I will make sure I have 3D pictures of each component I change

I replaced 15+ capacitors, everything I could think of or was suspect

The pictures I took of the original caps were blurry and I have no nice reference (BIG MISTAKE) When I went back to double check I could not see the positions

Maybe some idea of where to start

Much appreiciated from Scottsdale, Az

 

Attachments:

• Grundig 3028 under chassis (83 KB)

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Hi Don,

These days technology moves so quickly that I wonder if I'll ever be anything but a novice.

I have had a few similar models in for repair and the thing I found most confusing was the volume control. You would get the symptoms you describe if you had incorrectly connected C47 to the tap on the volume control, instead of the slider. I don't think you would have connected to one or other end, or you would have found the set to be either deafening or very quiet. I seem to remember that this capactor is located on the switch bank. It mght be good to check that all the switch contacts are operating correctly.

It is a good idea to take pictures as you go. Alas, the pictures I have are for a Grundig 5088 and the caps do not show clearly.

None of the sets I have repaired have had a functional "EM34" magic eye. I replaced one EM34 with a "UM4" (I had some in my junk box) using a small 12 volt transformer for the filament. I got a good price on an EM34 recently from Chelmer Valve.

Hope you come right - Bryce

 

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Bryce was correct in suspecting C47. After review I notice that C47 does not appear to be connected correctly. It should be connected to the 10M R29 resistor and it is in fact connected to the 220k R30 resistor.

The parts list shows C47 is a .022 125v capacitor. I originally replacd it with w 223k 630v cap

I now have a correct .022uf 200v orange drop to replace the 223k 630v capacitor for C47 so I will change that and connect C47 to the 10M R29. The .022 200v is closer to the original value with some B+

That appeared to work! The volume control is now restored

The tone needs some investigation as it doesn't seem correct, too brassy and not enough low end

 I tried a different EL84 but it did not improve the sound

The tone controls are functional and they do affect the tone, but there is a slight tinny presence in the signal. I would expect higher fidelity

Any advise on trouble shooting the tone. I will focus schematic tracing on the tone controls and, again, on changes I made to those circuits

 

Attachments:

• Grundig 3028 C47 image (187 KB)
• Grundig 3028 C47 schematic (114 KB)

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C58 was also not connected correctly which resulted in tinny sound. Now C58 is correct and the radio sounds great. Only thing left is a new EM34 and a new power cord

This was a great opportunity to get some more hands on training with vintage electronics

Thanks to all who participated

REMEMBER: Take lots of close up pictures

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