Hello, I need your help please. I've had several problems with my Marantz PM17 mkII for some time now which appear for a few minutes after switching it on: several slight bumps and a strong one on the speakers, delays in activating the input relays, the thermometer pointer remaining at 0; after everything has warmed up a bit everything returns to normal, except that if I 'knock' on the chassis I hear a corresponding slight bump on the speakers.
I opened the device and I understood that the area sensitive to the 'knocking' is the secondary power supply area (+ - 22 volts) at the top left looking at it from above, where there are two 1800 uF/50 volt electrolytics and various transistors/ic on heatsinks, two of which get hot enough to be difficult to touch for more than a few seconds.
If I 'knock' in this area, on heatsinks, electrolytics, connectors and neighbours, I hear the bumps on the speakers and I see the thermometer pointer falling to zero or recovering. The connectors are solid, it seems a matter of some component. In addition, at the foot of the electrolytics there is a white substance but I'm almost sure it's glue for fixing them because it's very tough at touch.
Has anyone had a similar experience and can advise me on what to replace (with my limited DIY and related measurement skills)?
Here's a photo made during replacing of output protection relay assuming the problems came from there, but that's only partially because all problems mentioned at the beginning remained and probably increased:
Thank you very much.
I opened the device and I understood that the area sensitive to the 'knocking' is the secondary power supply area (+ - 22 volts) at the top left looking at it from above, where there are two 1800 uF/50 volt electrolytics and various transistors/ic on heatsinks, two of which get hot enough to be difficult to touch for more than a few seconds.
If I 'knock' in this area, on heatsinks, electrolytics, connectors and neighbours, I hear the bumps on the speakers and I see the thermometer pointer falling to zero or recovering. The connectors are solid, it seems a matter of some component. In addition, at the foot of the electrolytics there is a white substance but I'm almost sure it's glue for fixing them because it's very tough at touch.
Has anyone had a similar experience and can advise me on what to replace (with my limited DIY and related measurement skills)?
Here's a photo made during replacing of output protection relay assuming the problems came from there, but that's only partially because all problems mentioned at the beginning remained and probably increased:
Thank you very much.
It's possible the transistors with heatsinks have vibrated and cracked the solder joints on the PCB. I would reflow the joints to each of those transistors before thinking about changing anything.
You are extraordinarily right, the soldering of all 3 pins of one of those semiconductors on the heat sink had a micro-fracture, probably due to an imperfect fixing of the same. Unfortunately, these heat sinks are only fixed with two pins so that if they are not in perfect contact with the board they can move by rotating around the axis joining the two fixing points, causing anomalous stresses on the semiconductor pins. With all gratitude.