@jafant Do you know if the No. 383 Integrated Amp has the cap issue like th other "3" series products?
I am not an ML expert by any means but my gut feeling tells me that this problem was limited to the 331, 332 & 333. The design of the electronics changes significantly with the later models. Most notably is the choice of moving away from T0-3 type power transistors. From a service perspective the newer design makes it so much easier to service. To remove a board that has T0-3 transistors requires un-soldering ALL the transistors because the legs of the transistors pass through the heat sink. (a real PITA). However, the newer designs with internally mounted transistors have a caveat. If they fail, they can fail violently and often will vaporize a board. I have seen pics of some of these boards. Not pretty at all. I think I said in another post that the ML amps are basically controlled lightning. They have massive power reserves that will destroy if unchecked.
The large caps on the 331-333 were problematic from a manufacturer perspective (Phillips). Oddly enough ML still chooses to install Phillips caps where most of the self-service community will install slightly larger Cornell-Dublier caps.
ML has identified a few counter-measures. One includes installing mylar strips on the frame of the chassis. I imagine the caps swell and contract, especially at initial power up. The caps are strapped to the chassis. I think the outer casing would eventually wear through the blue plastic coating causing the metallic can of the cap to contact the grounded chassis. If a cap is failing internally it would provide a path to ground for large amounts of current. This will heat up a cap quickly and then you get the black goo volcano. Don’t try to order these $0.25 "safety strips" from ML. They wont sell them. Don’t try and order large, small or so much as a decal from ML. They will not sell them.
Then there are a few other items that ML identified as failure points. These include soft-start resistors, small bypass caps and mid-level power supply caps at various locations.
I think by the time you get into the newer models such as the 336 and higher the cap problem had been well identified and fixes were already in place during assembly.
This however does not mean it cannot happen to ANY amp with large cans like the ML. As caps get older they start to become resistive. Resistance causes further heating and evaporation of electrolytic material. It becomes a run away train that cannot be stopped. If you have a ML amp with OLD large can caps by Phillips then be cautious and be prepared to spend a nice chunk of cash to make it right.