Quote:
Originally Posted by PJL
I suggest you do some resistance checks before trying to power up again. Set your DMM for resistance and check the probe leads are inserted in the correct +/- sockets. Putting the -ve on the base measure the resistance from base to collector then base to emitter. Repeat with the +ve probe on the base. Repeat for all 4 transistors on the PCB and the two power transistors. Then repeat the same tests on the good board.
Faulty T6 Base- bc=?ohms, be=?ohms: Base+ bc=?ohms, be=?ohms
Good T6 Base- bc=?ohms, be=?ohms: Base+ bc=?ohms, be=?ohms
Faulty T7 Base- bc=?ohms, be=?ohms: Base+ bc=?ohms, be=?ohms
Good T7 Base- bc=?ohms, be=?ohms: Base+ bc=?ohms, be=?ohms
And so on...
Post the results here.
A bit laborious but risk free, whilst using the lamp limiter can easily cause component damage as well as it being difficult to take voltage readings on the PCB when installed in the socket.
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Faulty T6 Base- bc= 36.28 k ohms, be= 52.40 k ohms: Base+ bc=36.44 k ohms, be=496 k ohms
Good T6 Base- bc= 36.45 k ohms, be= 50.15 k ohms: Base+ bc= 36.75 k ohms, be= 486.5 k ohms
Faulty T7 Base- bc= 2.536 m ohms, be= 1.083 k ohms: Base+ bc= 348.6 k ohms, be= 1.083 k ohms
Good T7 Base- bc= 42.5 m ohms, be= 1.196 k ohms: Base+ bc= 313k k ohms, be=1.196 k ohms
Faulty T8 Base- bc=5.63 k ohms, be=488 k ohms: Base+ bc=4.908 k ohms, be=438.7 k ohms
Good T8 Base- bc=5.12 k ohms, be=471 k ohms: Base+ bc=4.600 k ohms, be=429.4 k ohms
Faulty T9 Base- bc=351.5 k ohms, be=412 k ohms: Base+ bc=2.536 k ohms, be=7.18 m ohms
Good T9 Base- bc=316 k ohms, be=457.5 k ohms: Base+ bc=8.1 m ohms, be=9.22 m ohms
Output Transistors
Faulty Board Right Channel
Faulty - bc=5.718 k ohms, be=261.6 ohms: Base+ bc=3.883 k ohms, be=261.6 ohms
Faulty - bc=39.93 k ohms, be=270 ohms: Base+ bc=3.898 k ohms, be=270 ohms
Good Board Left Channel
Good - bc=5.581 k ohms, be=257.5 ohms: Base+ bc=3.920 k ohms, be=257 ohms
Good - bc=40.24 k ohms, be=256.5 ohms: Base+ bc=3.899 k ohms, be=256 ohms