Fixin' my ol' Vermona

[JimRayden]

I was just cruisin' around my summerhouse last week and it suddenly clicked into my mind. I had a Vermona electric organ collecting dust in the corner. We got it over 10 years ago for free because it was broke. Now I'm trying to repair it, and if nothing else, I could salvage some sweet effects from that thing.

http://www.vermona.de/htm/form2.htm

Alright, I've tracked the problem down to power supply, wich has two blown caps and one blown fuse. I also traced it, so you could follow me better.

http://ftp.taaviaudio.com/homes/JimRayden/PSU2.jpg

Q1: What could be the lil' thingies I marked with a blue '?'? They're shaped like transistors but have two feet. I'm suspecting they're diodes.

Q2: What are the little caps in front of the recto diodes for?

Q3: Note the "Exploded and disappeared" cap in the bottom. I don't know what kind of cap was there before. I have some 1000uF, 63V caps, can I use one of them at this place or do the voltage regulator need a certain size of cap there?

Thanks for the help,

----------
Jimbo


PS: Oh and it's nto offtopic because if I can't fix it into a synth, it'll turn into a guitar multi-effects box.

[David]

The design of that thing looks like it's broken into two identical units.  Could the "exploded" cap be a 100uF 16V like its counterpart in the "top" half?

If you know what the circuit needs, why not just build your own supply?

[JimRayden]

The design of that thing looks like it's broken into two identical units. Could the "exploded" cap be a 100uF 16V like its counterpart in the "top" half?

If you know what the circuit needs, why not just build your own supply?

Well, the top one has two 1000uF caps, and the bottom one has a 47uF one in their place. They might look like identical circuits but I'm suspecting the values are a tad different.

Oh, and why build a new supply when I can renovate the old one. It's just the matter of replacing a few parts. Right now I'm confused about replacing the lost cap.

Oh, and the input wires are ripped off the transformer, so I'll have to figure that one out too.

--------
Jimbo

[JimRayden]

Oh boy, oh boy, I'm getting closer. I just figured out the transformer leads, let's hope I won't blow any caps up anymore...

Hmm, can anyone comment on the "exploded and missing" cap replacement? Is it just a smoothing cap (the larger, the better) or does it have its effect on the operation of the voltage regulator?

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Jimbo

[JimRayden]

Come on, anyone?

-------
Jimbo

[MartyMart]

I'm no expert with PSU's but I would start with a 470uf 63v like the one to it's left.
See how that goes, it may well be a smaller cap, perhaps less that its
opposite above: 47 uf maybe ?
I dont see that harm will come from a "larger " cap !!

Marty.

[JimRayden]

I have a choice of either a 1000uF or a 100uF... hmm.... I'll go with a larger one to be safe?

regulated PSU's are a mystery to me too, I just don't wanna blow it up again.

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Jimbo

[JimRayden]

Alright, an update. The top half is working splendidly. It gives out a flawless 12V and doesn't heat up in any part.


On the other hand, the bottom part is giving me some misery. It's putting out -9V and 1,8V on the second output... Plus, the main voltage regulator thingy is getting pretty hot, although it's heatsinked.

I'll go and try to reverse the AC supply on the second circuit, I might get lucky. [EDIT: Just reversed it and no luck]

---------
Jimbo