smartin53
Well-Known Member
So I got an ailing MC423 car amp and am going through troubleshooting it. Basically the power guard light is on and the right channel is roughly halved in its output volume. A general inspection of the unit shows no major issues with components and nothing overheating. I can actually get both channels equal by adjusting the gain on the right channel so the audio path is clean functionality wise. After doing this and running for a while I again find no faults in a basic inspection.
This leads me to think that there may be a fault in the power guard circuit itself which is forcing the right channel into a lowered power mode. The one issue I could find was an IC that had some corrosion on a lead. Unfortunately I cannot find a service manual for the MC423 so I don't know if this chip has anything to do with the circuit or not. I might try to look at my MC431 manual to at least get an idea how the circuit might behave but I suspect they have different designs since the 423 is missing the PG terminal that lets you defeat the circuit if grounded (it just has 2 ON terminals and these are bridged by a lead on the circuit board too so both definitely have the same function).
While I wait to see if I can get a service manual from McIntosh (unless someone here happens to know of an electronic source that is eluding me) does anyone have any thoughts on what else might be causing this issue? Once I get this fixed I plan to repurpose this as an amp that I'll be mounting under the desk for my PC speakers.
This leads me to think that there may be a fault in the power guard circuit itself which is forcing the right channel into a lowered power mode. The one issue I could find was an IC that had some corrosion on a lead. Unfortunately I cannot find a service manual for the MC423 so I don't know if this chip has anything to do with the circuit or not. I might try to look at my MC431 manual to at least get an idea how the circuit might behave but I suspect they have different designs since the 423 is missing the PG terminal that lets you defeat the circuit if grounded (it just has 2 ON terminals and these are bridged by a lead on the circuit board too so both definitely have the same function).
While I wait to see if I can get a service manual from McIntosh (unless someone here happens to know of an electronic source that is eluding me) does anyone have any thoughts on what else might be causing this issue? Once I get this fixed I plan to repurpose this as an amp that I'll be mounting under the desk for my PC speakers.