Help!!! Some good days... some... not so good..

Linear and non linear

Re: Help!!! Some good days... some... not so good..

Postby Doug Coulter » Sun Oct 16, 2011 5:57 pm

I've seen that number both work and not work instead of 3055's -- DEC had some real big issues with that when I worked there (''70s). I'd guess that since the 3055's are so old you now pay a premium for them...getting rare. Hope those stay working! DEC tended to have PS issues, especially when they started learning to build switchers - they were among the first there, and many of the hard lessons now in the books are the result of things they found out doing that. I sure did replace a lot of them. One thing that took awhile to learn (for switchers) was that you don't put in max base drive when the power supply isn't full loaded -- burns out the base emitter junction and it fails "open" (I think the Pressman book mentions this). But you need full drive at full load, or the thing won't turn on all the way -- fatal that way too. That was a hard lesson to learn because they'd run for a goodly while with too much base drive before opening up, one by one, till the ones left couldn't hack it and fried (dead short). So one was left wondering which happened first when testing them all!
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
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