VintageTech
Member
I recently got a not working macintosh 512k. I replaced all electrolytic caps and the mac was running again.
My happiness didn't last very long though. The housing got very hot at the top of the Q2 (International 230v) during operation. I therefore assumed a defective Q2 BU 406 and a defective T1 flyback. I then replaced the Q2 and the T1. Unfortunately, the problem with the overheating Q2 has not gone away.
My question is now, could it be a bad T2 or the R11 Resistor reason for overheating?
Could be a problem in the neckboard of the crt?
Would it be possible to check the values in circuit with a multitester and find the bad part? Are there any important reference values to check? Why is the bu 406 overheating?
I already measured the values of the bu 406 to ground.
I have got:
Base -82.0 mv
Collector 20.49v
Emitter -22.0mv
My happiness didn't last very long though. The housing got very hot at the top of the Q2 (International 230v) during operation. I therefore assumed a defective Q2 BU 406 and a defective T1 flyback. I then replaced the Q2 and the T1. Unfortunately, the problem with the overheating Q2 has not gone away.
My question is now, could it be a bad T2 or the R11 Resistor reason for overheating?
Could be a problem in the neckboard of the crt?
Would it be possible to check the values in circuit with a multitester and find the bad part? Are there any important reference values to check? Why is the bu 406 overheating?
I already measured the values of the bu 406 to ground.
I have got:
Base -82.0 mv
Collector 20.49v
Emitter -22.0mv
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