MC 2125 Issues.. Terry..or anyone?

Turned my 2125 on today and went to turn it off and now the power knob go's round and round, both directions but stays on all the time.

All power guard lights are out . I'm sure its on the vertical board behind the PG, lights the 2 caps (which ones, what values?) and the 2 - 1n4004 diodes (correct me if i'm wrong) The bulbs are good.

On power up, you never hear a relay click on and on power off you can hear the caps "draining down as the music quiets" if the source is still playing, leading me to believe the relay is stuck on all the time.

I think the relay contacts are welded together? I haven't open'd her up to see, pending the reply's I get here. If so how/ why? Is the relay on top of the board or bottom? I'm sure I can download a schematic if I don't already have one, But if anyone has picture that would be better.

I will take pictures to document step by step what I do and post to the thread the steps and issues I run into, to help others, depending on possible cost. I may just leave it alone for now if too expensive.

The unit plays well other than these 3 issues..the Power guard lights have been out since I got it, along with the relay issue. Now I want to fix them, along with the power switch issue since I have some time. Could I un-weld the relay points and burnish the points? I am running on a tight (almost non exixtant budget as I am out of work and looking for a job in the Auto industry as a mechanic, and times are tough. I should have saved some dough and bought a few less McIntosh pieces and I would have a nice sack$ to fall back on..kidding.... no regrets here, when the money's good it's good.

BTW, I don't hear the relay click on/off when I use the speaker switch either. Right now it stay's plugged in all the time on a selectable power cleaner/ supply, so I can control on/off from there. That way it isnt on 24/7.

This amp is in bridged mode, running a MC center channel with no other problems. It will run in stereo fine as well.

Thanks for any help, :thmbsp:

Phil

It sounds like your power switch is kaput - check with AC or McIntosh. Flip it over, take the bottom off and the relay should be obvious. If you take it out, make sure you take pics and make a map of where the wires go as this detail may not be on the schematic.

You can try cleaning the relay but I've had limited success with this.

C-307/8 are a couple of caps on the ps board under the dust cover that should be replaced along with the diodes that are right there, D302/3.

Murray

The power board has failed, probably not just the 2 big caps and diodes.

Would the unit still play and function correctly if the power board has failed? Just PG lights out and no relay click....wouldn't the whole unit be inop, not just the Power guard lights and the relay?

Again it still plays fine and sounds good in 2 channel and bridged mode?...


Interesting..

Phil

Board has 4 functions, + and - supplies for meter board and drivers, relay driver, lamp drivers and power for normal and PG lamps. The relay supply and lamp supplies share the same source, as long as the + and - supplies are working and the relay closed the amp will work.

Proper Power Guard Board Component Layout:...

Except for the main power switch on the front, which I have under control, could this be the whole problem, including the relay issue? See the stuff leaking out of the cap on the Power Guard board?

Question1:
the capacitors have arrows to indicate polarity. The new ones will most certainly be marked with a +and-. Which end is the arrow pointing to the positive or negative side (+or-) for the new cap to be installed correctly?

Question2:
the diodes in between, how do I match the new ones position to the old ones? Should I put the lines on the end of the new 1n4004 diode's where the line on the old diode lines are printed. I don't want to smoke this board.

I have noticed both diodes and capacitors are mounted in opposite directions..this is correct yes..? I want to make sure no one else has been monkeying around with this amp.

Thanks to all in advance,

Phil

All looks correct, follow the banded ends of the diodes and insulated ends of the caps are the + ends.

Yes, I just found it on google after staring at it for a while. So the black plastic end is the positive...the one with the hole I see leaking.

The Diode has the cathode or nedative side where the stripe is ..correct?

Thanks Terry,

Phil

The cathode side is with the stripe. Verify placement with the schematic.

The metal end of an axial cap is negative.

Murray

thanks guys, now I have to hope this cures all but the power switch issue. New power switch coming from A/C is 26.00.Hopefully these 2 diodes and 2 caps will bring her up to working speed again.


Again,Thanks,

Phil