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Old 20th November 2004, 11:51 PM   #1
Bose(o) is offline Bose(o)  Canada
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Default Old Receiver

Hello all!

I have an old receiver from my Dad and the right channel is heavily distorted. Anyway, I've measured the amps and regulators...nothing looks black or brown. Found a grounding problem and fixed that.

Now it doesn't go POP! when you turn it on.

However I found one of the chips, not exactly sure what it is yet, measuring out of spec with the others in the circuit. The following is written on the chip (B699 BL3). I'm hoping it'll ring a bell in someon's head.

I know the amp was built in the mid 70's. I just need to find some kind of replacement for the ONE bad chip.

TIA, Brodey Dover


EE student at Univeristy of Ottawa
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Old 21st November 2004, 01:03 AM   #2
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Sounds like a 2SB699 transistor... 160V, 12A, 100W.

What you you mean, 'measures out of spec'?
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Old 21st November 2004, 01:08 AM   #3
Bose(o) is offline Bose(o)  Canada
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If I measure from Ground and ouptut of the transistor then I'd get a resistance value below that of the other transistor's on the circuit.

Receiver is rated 100W RMS, I'll check it out.
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Old 21st November 2004, 02:38 AM   #4
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Pull the transistor and do a diode check on the thing.
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Old 21st November 2004, 08:06 PM   #5
Bose(o) is offline Bose(o)  Canada
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Diode checks: Pins on transistors go like CBE? Collector base emitter?

Would the diode check be between the Collector and Emitter.

I appreciate your help.
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Old 22nd November 2004, 12:09 AM   #6
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Diode check from base to emitter, then from base to collector. Both should show a standard forward voltage drop...something like 0.4V to 0.7V. With an NPN transistor, positive on the base and negative on the emitter and collector. Then check collector to emitter, first with positive on the collector and negative on the emitter, then reverse...negative on collector and positive on emitter. Should read nothing measuring from collector to emitter.

Of course, check a PNP transistor with the leads reversed...negative on the base and positive on the collector and emitter... Same deal with the collector to emitter check, there should be no conducting with the leads in any configuration.
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Old 26th November 2004, 07:17 PM   #7
Bose(o) is offline Bose(o)  Canada
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Okay, its BCE.

BE measures as: 0.518V

Shall I check others?
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Old 26th November 2004, 07:58 PM   #8
Bose(o) is offline Bose(o)  Canada
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30 min. limit to edit messages grrr...

Okay, its BCE.

BE measures as for B699 chips:
1. 0.518V
2. 0.520V
3. 0.522V
4. 0.521V (So, all 699 chips are good).
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Old 26th November 2004, 08:22 PM   #9
Bose(o) is offline Bose(o)  Canada
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D735 chips are NPN, 699s are PNP.

1. 0.521V
2. 0.528V
3. 0.528V
4. 0.530V

The main problem was a HEAVILY distorted right-channel. Left-channel was beautiful. I thought that distortions that I was hearing would be caused by the transistors.
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Old 26th November 2004, 09:20 PM   #10
Bose(o) is offline Bose(o)  Canada
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Wow...sorry guys.

I either can't type or see or, both.

Anyway the 699s read as:
1.0.537V
2.0.531V
3.0.527V
4.0.521V

I do believe that +/- 0.016 V shouldn't matter much, but that's my opinion. What do you guys think?
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