Need to fix hum...(nordmende isabella E)

[cam2000]

Hi guys,

well, i did all of that, sourcing some new caps here in Syd.
AND...
The hum is still there. At first it was, then it wasn't, and now it is definitely here.

Ugh. Where to next?

 

[cam2000]

Is it right to say if i'd soldered it incorrectly, that it wouldn't have turned on? Or played music?

 

[cam2000]

Another thought - it is a two-prong power socket. It has a separate ground out. In the rear of the unit. Might this have something to do with it? If so, how do I ground it?

 

[nj pheonix]

Antique audio sells can caps that match a lot of things. If real estate is as tight as some say you may want to look for the can caps there

 

[Dandy]

Have you joined the radiomuseum.org website to gain access to the schematic yet? If you offer to write up your experience of working on this radio, you should get membership.

The powersupply caps probably needed replacing anyway. Looks like there are others to replace now.

 

[gadget73]

It would be worth checking the power supply voltages to see if they look right. If something was wrong with the cap replacement, I'd expect to see the voltages be messed up as a result. It might also be worth doing a quick and dirty check of the selenium rectifier to make sure its not shorted. As long as it reads open one way and some voltage drop the other, they aren't terminal. A dead short both directions will kill your filter caps and make it hum horribly. I'd also expect the power transformer to be getting hot if that were the problem though.

 

[Dandy]

A bit more reading for you. http://www.audiokarma.org/forums/showthread.php?t=226184

He mentions needing to replace 38 capacitors, all of which were defective. I'm sorry that I didn't ask earlier if you can read a schematic. Without this it will be difficult to identify where to measure the voltages.

 

[cam2000]

In the process of joining radiomuseum. They seem very serious there.

I've not really read any schematics, but I do have a physics degree and we touched on a few things there. Then again, that's nothing like hands on experience.

But I feel I could get my head around the whole thing.

 

[Dandy]

In the process of joining radiomuseum. They seem very serious there.

I agree that their serious approach is a little daunting, but probably in a good way. You do need a schematic and they may be able to help with this German unit.

There's no substitute for learning to read a schematic. Nor is reading one difficult. Understanding the nature of the circuit is something else, but seeing what connects to what is essential.

You're on your way.

 

[cam2000]

Okay - joined the group - they are sending my password via mail. Which might take a little while to Australia. Oh well. On the way at least to getting the schematic.

 

[Dandy]

Password via mail! Wow. No harm in reading up on general servicing procedures for tube receivers in the mean time. BTW, what is the exact model number of your unit?

 

[cam2000]

It's a Nordmende Isabella E. That's all the info I can find in regards to model on the unit, unless I'm missing something.

 

[Dandy]

Thanks. I see that the Radio Museum has a schematic for that model, so you'll be good to go, when you password arrives.