any tips for MCR power supply rebuild?

kstillin

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OK-

I've had this Bob Roberts kit for about a year and a Spy Hunter and a Tron in need of a power supply.

I attacked it tonight (phase I) and had the most trouble. The difficulty was in removing the transistors attached to the large heat sink. The two leads to the TO-3 transistors are connected to solder pads on BOTH sides of the board, and one of the sides is UNDERNEATH the large heat sink.

I wound up tearing up a trace and lifting two pads that don't connect to anything. I resorted to mechanically flexing one of the transistors to break away the leads to allow me to remove the heat sink. Then I was able to clean the holes without the heat sink in the way.

Is there a better way?
I don't really see how I'm going to be able to put this back together. There are some blind traces under the heat sink that have to have a lead soldered to them. I can resort to using a socket or running a wire lead on the non-parts side back to where the transistor connects.

That'll make it look pretty hacked though.

Any good hints? The design doesn't lead to any ease in replacing these transistors. I was trying to pry up on the transistors while applying enough to heat to melt the solder on the side under the heat sink.

Thanks for any clues.

K

Maybe I'll ask Bob Roberts- he says he's done HUNDREDS of these- NO, THOUSANDS...
 
Work slow, ADD more fresh solder, then remove.

I have a Hakko 808, but have done it with a sold-a-pult a few times.

You will need to learn the balance of when to get the solder. Practice on old junk equipment... Those are on everything... Atari's AR I~II, and there waiting for you on the Willams Pinball power supplies when you go that direction.

My first MCR rebuild actually went quite smooth, and fixed the issues in my Spy Hunter.

Lifting a trace is a bad feeling... done that once or twice.

-Mike
 
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