Shorted Output Transistors, Fuses Blowing

[gslikker]

The TO-66 was almost gone, but apparently some are back, made by Central Semiconductor, even a 4 Amps PNP type usable for old amps is there. (I could not find a 4 Amps PNP type for some time). Watch out some types are darlingtons.
Select TO-66 and TO-66-2 at Mouser .
Expensive, they are........

 

[Bob]

we're jumping around here.

VOM on any two pins that yields 0 resistance means it's shorted and therefore BORG'd.

testing pulls with missing pins means there's the possibility that the metal flat-portion
is electrically the active (and missing) pin. you will need to look at the datasheet to confirm/deny.

you would do well to look for modern day equivalents for the simple reason that, if you buy NOS
and the circuit still has problems, you will blow the (expensive/rare) replacements.

 

[gslikker]

just posted in another topic: the easiest way to protect old sansui main amps, because the power fuses are usually accessible from the side.

 

[Gazzy]

Thank you all again for your help!

She's been up and running for several hours since I replaced the output transistors, no issues, running nice and cool and sounding good. Now to tackle the dead tone pots and lack of bass...

I best start another thread

 

[dlucy]

I doubt that you will be able to plug the TO-66 case transistors into the test jack on your meter, so you'll have to test them the old-fashioned way.

If/when you find failed output transistors, you may also find that they are no longer available. A TO-220 case device will probably have to be fit into its place, something like this:

MJE15030G and MJE15031G should be suitable replacements for your two output types.

From a manufacturer's application guide:

 

[Way San]

Thanks for posting the subbing package diagrams. Saved me a lot of time.