Carver PT2400 insight needed

[Mick Bailey]

This amp has repeatedly been put on the back burner so I've decided to dedicate some time to fixing it - the RH channel is stuck in protect mode.

Does anyone have any general advice or specific approach to working on this particular amp? The manual suggests that it shouldn't be dismantled in order to troubleshoot, but that appears to be counter-intuitive as it's so tightly packed. It's an early rail-switcher, with the added feature that the incoming mains is also controlled. So, everything works, or everything doesn't - no in-between.

[Enzo]

I don't know if I have that manual or not. Is the do not disassemble warning like a "no user serviceable parts" warning, or is it on the schematic per se?

[Mick Bailey]

The intro to the schematic suggests that removal of parts should be kept to an absolute minimum and to locate the defective area using in-circuit analysis. With this in mind I'm wondering if there are some specific tricks to analysing faults with this design. I can understand the approach - a bit like SMPS diagnostics in that it's a closed-loop and simply disconnecting a board or section may not work out.

The mains is controlled by an optocoupler and triac, so in protect mode the channel is dead - no power to the primary. My thought was to short out the triac so that the amp could be run up on the variac (with bulb limiter) to at least get to the point where some voltage and current readings could be taken. I don't know if this will work, or whether this is unsafe to do in terms of causing more damage.

The schematics are 33Mb so I'll try to cut this down and post them.

[Mick Bailey]

The available schermatics are very poor quality. Here are the pages that relate to the amp;

Carver PT2400.pdf