Hi everyone.

This is my first post, and i have to congratulate and thank this increadible initiative. All About Circuits was one of my main learning resources when i started tinkering with electronics, some 9 years ago i think. I still have lots of printed chapters arround.

I was a kid musician and started learning about electronics by making guitar pedals and studying from here and also some good books. I then whent to university (audio engineering) and now i run a small electronic instrument repair shop in Lisbon. I have been repairng many analog synths, organs, microphones, recording gear, etc.

THANKS!

Now i have one question. I just bought a small italian combo organ Crumar Cougar. Its very obscure, and i couldn't find any info about it online, rather than a very lame video on youtube with a guy running the keyboard.

It is a combo organ with integrated speakers and power amp.
The power amp is all germanium and i think was made by another company (ELMAR?).
There are these two components im not shure what they are, i will attach some photos.One on the power amp board, the other flying in the output of the power supply.

The red one seems a zener in the output of the power supply, that regulates the -12V rail that powers the germanium power amp....but im not shure, its magic smoke escaped already.
The other one seems a capacitor but im not shure.... it is located in series with a 10 ohm resistor across the trimmer in the bias VAS stage of the power amp. Could it be some kind of decoupling cap to the trim? is this usual? It reads 20 Ohms though.

Hope some one can give me some clues, many thanks,

Rui

 

That certainly looks like an old IR maybe germanium diode, if you can trace the circuit and confirm a 12v zener, then you should be able use a modern silicone replacement, the other comp. looks like a VDR of some kind.
Max.

 

International Rectifier (that is their symbol on your diode) list a IZ12T10 silicon zener from that era.

Max zener current 80 mA, max dissipation 1 watt.

Cathode to flange.

I concur with Max the other pic is of a VDR or thermistor, perhaps used for soft start

 

germanium amps used temprature compensation, they were prone to thermal runaway. a thermistor in the bias for the outputs would be reasonable.

 

Many thanks, i think you guys nailed it. Its almost 100% certain it is a zener.
I didn't thought about the temperature compensation resistor in the bias circuit. It must be, and in that case the part seems to be still working, wich is great, because i dont think i could ever find data to get a replacement.

Many thanks.

 

Is it me, or does the top capacitor look like the top is bulging up?

 

Is it me, or does the top capacitor look like the top is bulging up?

I think it is the curved break-away groove that makes it look bulged. Look at the curve on score mark on the one just next to the one you refer to.

 

Looking at the photo i thought the same, i cheked but it was just an illusion. And also they are brand new good quality panasonic fm caps from Mouser.