MA5100 driver transistor subs - slip of a screwdriver = disaster

creeve

Active Member
So I am an idiot, I am in the process of restoring this new piece in my collection and was scraping a solder blob off the chassis near the mounting nut for q27 aka q216 in the SM. Still had not discharged all the caps and shorted the base to ground, sparks flew and now I have shorted outputs on that channel. I know the replacements for those are MJ15003G but I have found no definitive answer on the three TO66 drivers. Just following the old rule of thumb replace all drivers when outputs have been shorted. Has anyone found a tested modern replacement? or have I just made this thing into a pretty paperweight? Any help would be greatly appreciated.
 
Those old to-66 drivers are pretty tough.....I would not assume they are shorted until you test them.

That said if you order them from Mac parts you will receive selected NTE replacements.....NOT THE ONES from the NTE cross reference.....they do not meet Macs specs.
 
Those old to-66 drivers are pretty tough.....I would not assume they are shorted until you test them.

That said if you order them from Mac parts you will receive selected NTE replacements.....NOT THE ONES from the NTE cross reference.....they do not meet Macs specs.
I will test them, so you would trust them if they pass a simple dmm diode test in all directions? I will report back later with the results. I thought I read a post somewhere in all of this that said mac no longer had subs for these either. I think in one of your older posts you were testing some subs but had oscillations.
 
I will test them, so you would trust them if they pass a simple dmm diode test in all directions? I will report back later with the results. I thought I read a post somewhere in all of this that said mac no longer had subs for these either. I think in one of your older posts you were testing some subs but had oscillations.
BTW I am not afraid to convert to newer package style either. Despite my stupidity that caused this mess I am capable of such a conversion if such a thing is possible.
 
so you would trust them if they pass a simple dmm diode test in all directions? I will report back later with the results.
I agree with c_dk, those trannys are tough. So test them and if they pass, install, fire it up and report back...
 
Well I am happy to report they all pass the 4 way dmm check. I am shocked considering I arced the screwdriver right through the base of one of them. They are apparently more robust than the outputs. I will install them on the good channel and see what happens. I would rather test with those than two brand new ones, I am going to replace all 4 anyway so everything is matched. I will let everyone know what happens. Thanks.
 
well I just installed the drivers into the good channel. Although they are not shorted and passed a basic dmm test, they must have been injured because that channel becomes extremely unstable with them installed. DC offset swings from 4mv to over 200mv up and down erratically. power supply becomes unstable as well, panel lamps dim etc. They must have damage to the junction causing leakage that only is apparent when in circuit. They need to be replaced. So if Mc Parts does not have subs I am going to need to find modern replacements.
 
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