Hello, I have a Marantz PM7200 and for several months now I've been having a the following problem. Every now and then the sound crackles or disappears on the left, right or both speakers. I'm quite sure the problem is not with the speakers as I tried using a different set of speakers. I took the amplifier to the shop for repair but they said they found no problem with it. So I brought the amplifier back home, set it up, ckecked all the connexions but I still experience the problem. What can I do? Thanks in advance.

Try wiggling the speaker cables where they connect into the PM7200. If it crackles get the shop to check for 'dry joints' in the unit. It is quite normal for things to look ok and to work perfectly in the workshop, but that is not a good test. Dry joints are quite difficult to spot and any soldered joint 'looks' ok, but if the soldering temperature is a bit off, usually on the low side where the solder is only just about hot enough to melt, it will result in a what we call 'dry joint'. It is not unfrequent to get this problem with production line processes as there are many factors on the assembly line that can effect the tip of the soldering unit. It can be as simple as someone getting up out of a seat and changing the air flow that then causes the soldering tip to cool slightly. We are taking 'parts' of a degree temperature changes. The shop should have equipment to test the conductivity of soldered joints. A light hand during testing is a prerequisite!