MAC 4300V Repair Question for McExperts

[FRANK DUVALL]

I have a McIntosh 4300V on my bench that has a big problem...after operation for 1 to 3 hours this pig locks up!? There is no sound, only partial display segments and no response to any buttons. It must be unplugged to turn off. Even after a cool down period it sometimes remains locked up sometimes even after a few days?
I'm guessing it has something to do with the digital board that is controlling everything but I have cleaned all of the connectors and re-seated them thinking that was what was needed. We all know that intermittent's are a bitch. Anyone out there seen this before and know where to look???

Merry New Years and Happy Christmas to all you tweak heads out there!

AlleyGator ;-)

 

[clinic-audio]

Welcome on AK

I will take a look in power supply first.

 

[c_dk]

We usually don't call our stubborn obstinate children those kind of names in this forum.......we do make them bend to our will though, eventually.

Sounds like contamination is shorting out the logic switch pathways causing it to lock up with a command that is over riding all other commands. Corrosion that makes and breaks are intermittents that can drive you nuts. You probably can buy a schematic from Mac parts and then it is a matter of careful cleaning with alcohol......the unit's pathways not yourself.

 

[dewickt]

The 4300 can have switch problems, soak the push buttons with DeOxit D5 to stop multiple bounce problems, and work on front panel and circuit board position to stop them from hanging up when pressed. If one of the buttons stays depressed it will hang the processor !