GK400RB-III 1 output blown

[T9c]

Have just one of the six OT's blown, the NPN - 2sc5242. Emitter resistors, drivers all check good.

What is the general consensus on replacing outputs on these? If one is bad, throw 'em all out, or is single replacement ok?


I have replaced lots of them singly or working pairs (MJ types) in earlier model RB's before, but this is the first of this series I have worked on.

[J M Fahey]

Start by replacing the bad one, and see what happens.
Do not plug it straight into the wall outlet, use a lamp bulb limiter or raise voltage *slowly* with a variac while metering the AC current consumption, just in case "something else" is bad..

[Jazz P Bass]

As always, buy the replacements from a reputable source.
Rant: What I don't get about the 'counterfeit' creeps, is how much more difficult is it to make a knockoff part correctly?
Or better.

[J M Fahey]

I guess "the process" itself must cost about the same, but probably the better ones have some proprietary manufacturing tricks, which the counterfeiters ignore.
What is unforgivable is skimping on the "copper coin" heat spreader used between chip and steel case.
Counterfeits often use a much smaller one (such as the red script "Toshiba Japan 2N3055" sold by everybody, including reputable dealers), and some s.o.b's avoid it altogether, attaching the die straight to the steel.
It may be an "electrically" good chip, will pass tests (such as curve tracers) fine, yet die on the first show.

The "Toshiba" I mentioned has a *good* chip, just you can't extract full power.

[sgelectric]

ttttttttttttttt