I purchased a Marantz PM-94 integrated amp in 1991. Fantastic amp with smooth and sweet sound. Only problem is that the amp has blown its left hand channel on me 5 times! First 4 times were covered under warranty. Last time the repair technician (and I think this guy is very good) said he couldn't trace the fault - he would have to spend many hours on it to trace the problem to whichever component was faulty. Marantz are no longer interested in fixing this even though the fault has been there since very early in its life.
Question - Has anyone else had a problem like this with a PM-94? And any thoughts on how to approach Marantz for further help?
Marantz has changed ownership over the time you have owned your amplifier. I seriously doubt the new ownership is that interested in dealing with a repeat problem from another company. You are talking about a 14 year old amplifier. I understand the problem has been there since it was new; but that should be the best indication it is time to move on.
Hi, I had the same problem with my PM94: one channel blew up (real smoke...), anyway; searching the net i was able to find the schematics and adjustment procedure. I bought new FET's and other transistors and replaced them. Also i replaced all elco's in the end-amps. After adjustment it worked again. Took me some work but it was worth it. If your'e interested, i can give you the information i got.
All FET's, transistors and elco's cost me about 150 dollar (i now have some spareparts...)
By the way, the probable cause for the amp to blow up was likely the connectors which connect the two pcb's; every time the amp heats up, a mechanical tension is created between the two pcb's. This and the fact that the solder oxidates faster because of the high temperture, causes the connector to loosen. As a result the FET's are no longer 'under control' by the electronics and they burn out. A solution would be to replace the connector by wires or to resolder the every 5 year or so...