V276 preamps: Corrosion on leads of input transformer

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Salossi

Well-known member
Joined
Aug 23, 2006
Messages
51
Location
Cologne, Germany
Hi folks,
I currently have a problem with my V276 preamps, made in ´69...

I own 5 of these preamps, and I use 4 of them all the time... the 5th unit had a technical issue and was sitting on the shelf for years - I also used it to take out some spare parts to repair the other units...

A few days ago, I recognized that one channel of my 4Ch-V276 Box is not working… No signal at all…  :(

At home I spotted, that those thin wires coming out of the input transformer are pretty much corroded… I tested the coils with the component tester of my oscilloscope, and by comparing to the other (not working) unit I could immediately spot that there is an open connection at one coil (where I could detect a coil at the other unit).. on the other hand, this already broken preamp also had another bad coil - probably this was the reason, THIS second unit didn´t work in the past…

Anyway I swopped the transformers, being extremely careful with the wires…
After I installed the other tranny, the coil, that was still working beforehand, was also dead :-(
FFS!!
It seems as if those thin wires are EXTREMELY brittle, as they probably are completely corroded…

I would like to repair those trannys now, I hope that maybe the corrosion is only an issue at the outside of the shielding, and maybe I can clip of the wires inside the magnetic shield, resolder and then reassemble? What do you think?

My questions are:
- Is this a common issue on those trannys?? Or is this problem maybe caused by humidity at the previous owners place or whatsoever???
- Did anybody restore / rewind one of those trannys already? Does anybody have a schematic (winding diagram) of those input trannys, used in the V276??
- Is there any other accepteable option for a replacement?
- Any ideas, how I could protect the leads in my other 3 still working preamps from the same issue?

Cheeers, Salossi
 
Complicated to post images here - I´ll try...
Here´s the corroded wires...

Not working, 404 error - any option to upload images here? I have nice closeups of the wires / dismantled transformer...
 
Hi Salossi!!!

Sending you schematics of this preamp!!!

I advice you that you not a lot picking with this wires,they are so sensitive and you can destroy them!!!

This preamp are prone to be corrosive,so I advice you only try desolder place around trannie and solder again!!!


Inductors of this preamps are Dormel and they not exist anymore and hard to get them....

 
Your pic are not visible Salossi!!

Replacing transistor for this preamp are:

SST117/116-2N2219A

BCY 58/66- BC109C/B
                            BC550C/B
 
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