Mark Levinson 436 problems

[louislouis]

one of my ML 436 amps shuts off about 3 seconds after being turned on. The problem does not exhibit when it is at the local dealer's repair shop, but always does so in my house. The amp is one of a pair; and each is connected to its own 20 amp dedicated circuit. The amps were upgraded a few months ago, but were behaving the same way before the upgrade. The other amp is fine. Does anyone have an idea of what may be going on? I would not like to have to buy a new set of power amplifiers. The ML 436 sound so magical when they work.

[rbinck]

You could try swapping the speakers between the two amps as a test. There may be a problem with the speaker or wiring that causes the amp to overload. If the problem moves to the other amp, then you know the source of the problem.

[louislouis]

I did try swapping the speakers, swapping the power cords, swapping the interconnects. The only swap that had any effect was swapping the interconnects and the power cords at the same time. Doing so restored normal function for a few hours, or a few days; but then, the power indicator light on the front of the amp dimmed, and when I tried to bring the amp out of stand-by, the amp failed and continued to fail. My technician at the local ML dealer suspects a circuit board that is discolored, but ML will not provide one under warranty from the upgrade. This board was not replaced during the upgrade. I may have to buy it myself. Any experience with similar problems out there? I thought that buying amplifiers that cost a lot of money would mean that they would last a long time.

[rbinck]

Ok it sounds like a heat issue. I use a Raytek MiniTemp MT6 heat gun to track down these problems. It may be as simple as adding additional ventilation in the cabinet. May also be why it does not fail at the shop.

[louislouis]

Thank you again for your reply. The problem exhibits itself on start-up from cold as well as after the amp has warmed up. The power indicator light blinks rapidly, which the trouble-shooting part of the ML user guide says is indicative of a heat problem. But, the problem occurs when there is no heat. I have asked the local dealer's technician if it could be that they heat sensor is malfunctioning, that is, the heat sensing part of the circuit. It seems to me that if the heat sensor is a separate part of the circuit, and not inbedded in the motherboard, it would be less expensive than replacing an entire board.

I had hoped that this was a frequent-enough problem that others had found a solution.

[rbinck]

I doubt if it is a common problem. The thing is since the PC board is discolored, it may be that a component has broken down due to heat in the past and could be the reason for the sensor detecting high heat. I guess you are looking at sending it in for repair. I'd send it to the factory. Some manufacturers have a flat rate for repair. Worth checking into.