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Beomaster 5000 - do they all fail in the same way?

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Jeffrey P Brooks
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Jeffrey P Brooks posted on Tue, Oct 19 2021 7:26 AM

I am trying to repair a Beomaster 5000 that had some failures on the amplifier board.   I have two others that I bought for parts.

I started looking at the darlington transistors and I found that they were all bad.  When I say bad, I'm saying they failed the normal "transistor test" with a multimeter on the diode setting.  For example, the BDV64B (PNP transistor) showed a reading with positive on Base and Negative on Emitter.  And for the BDV65Bs, I had a reading with negative on the base and positive on the Emitter.

I took the transistors out of all 3 boards and most of the 12 transistors had failed as described, although a few had some opens that should have had a reading.

What is the deal with this receiver?  Are these darlington transistors not tested in the normal way?

I also pulled all of the BF857s and most of these are good.

I've checked the DC power levels and they look good.

Are there other transistors that commonly fail that I should remove and test?

Does anyone have a favorite substitute for the darlington pair?

Appreciate the help!

Jeff

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Jeffrey P Brooks
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United States
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The darlington pair is BDV64B and BDV65B.   Mouser has a BDV64BG which I assume works, but they are out of stock until way into 2022...

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