McIntosh MC-2155 Big Filter Caps Source

[MACKIE1975]

Just found a pair in my collection and knowing that it is in working condition prior removed. Just can't tell which McIntosh is for.

 

[kevzep]

View attachment 1214748

This is probably the 6th bad main filter cap I have come accross in a McIntosh amp! A MA6200 in this case, over the last 40 years.....

Monitoring the main supply to the 18 volt + DC regulator. Supply voltage has sagged to 24 volts from the expected 39. Amp is in full power guard at 10 watts.

Also had a interesting problem with improperly installed drain resistors for new main filter caps in a Pioneer SA9900 allowing oscillation which would trigger the protection circuit after about 15 minutes.

Ha, interesting, I have something similar going on with a Crown Macrotech, AND and Sansui G9000......all this gear is getting old now, these things have to be factored in now, and also considered with fault finding....

 

[c_dk]

A bench stress test is the only way I know to really determine if the caps are truly failing, or in this case were one has actually failed.

In the case of the Pioneer, wrapping the bleed/ drain resistor leads around the screws to make a marginal connection was just questionable at best. Of coarse the high frequency hash on the o'scope kind of gave it away.

One of DOB's old test clinic bench procedures was to break loose and retighten the main filter cap screws for the main filter caps whenever he had the time to remove a amp's bottom cover.

 

[kevzep]

A bench stress test is the only way I know to really determine if the caps are truly failing, or in this case were one has actually failed.

In the case of the Pioneer, wrapping the bleed/ drain resistor leads around the screws to make a marginal connection was just questionable at best. Of coarse the high frequency hash on the o'scope kind of gave it away.

One of DOB's old test clinic bench procedures was to break loose and retighten the main filter cap screws for the main filter caps whenever he had the time to remove a amp's bottom cover.

I have a arbitrary wave file use to stress test amplifiers, I agree, it really is the only way to properly test the main caps.

I am not a fan of the wire wrap I have to say.....

 

[quartersaw]

At idle, my 39000uF caps rail tested at 39 volts on both of my Mc2300's.
They aren't leaking, so I assume this is OK..

 

[c_dk]

Need to put the amp under stress. I test with 20 hz into my load box and monitor the distortion and voltage as the amp approaches it's rated output.

The pic of the MA6200 I posted early this week would go into PG at 10 watts at 2000 Hz.......hardly much stress but enough to show up a faulty cap in that unit.

 

[nbndtrain]

Just found a pair in my collection and knowing that it is in working condition prior removed. Just can't tell which McIntosh is for.
View attachment 1214802

This is an old thread, but most likely those are misprinted 18,000uf caps for an MC-2155. Are you sure these weren't the ones you replaced? I believe McIntosh sells the misprinted caps as replacements for the MC-2155.