2. amps-preamps
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re capping

I hear the phrase 'recapping'. when do you know when you should 're cap' an amplifier? I have a McIntosh mc602 amp that sounds fine to me. I also have a McIntosh mx132 that works ok for me. I also have a bose 901 series 2 active equalizer that seems to work ok. the 'red' on light kinda flashes now and then. if my system sounds ok, should I worry about my units?
128x128g_nakamoto
trombonist's avatar
trombonist
28 posts
 
So to this end of "knowing the circuit b4 recapping" .. I know the Counterpoint NPS 400 has been talked around the board a bit .. anyone know a tech who is proficient in Counterpoint? Mine will give a mild pop in one channel when powering up, no crackling or any other symptoms that I detect during play .. but am assuming caps are the issue? Built in 1996 btw.
partroysound
25 posts
 
When you recap a 30 year old amplifier do you change the big power supply caps or do you replace all of the circuit board caps?
minorl
1,016 posts
 

the problem would be with the electrolytic capacitors.

Therefore, I would plan on replacing all the electrolytic capacitors with like value and size capacitors.  However, the number 1 priority would be the power supply caps.  They are typically the easiest to get to and replace ("typically").  The problem is finding the correct value and physical sizes that will fit within the allocated space and clamps (if used) available.

There are a few manufactures out there and a few retailers that will sell the large capacitors.  If you are replacing, then you really want new caps.  You can find NOS unused caps, but they would be just as old as the ones you are replacing.  However, they will not have been subject to the extreme heat from use.  They may (read should) be connected to a variac input first to reform them slowly.  But first try for new. 

Also, by-the-way, you definitely do need to look at the other electrolytic caps to see if they are demonstrating problems such as leaking also.

If, after inspection of the circuit board caps and the power supply caps there is no obvious issues, then take your time in planning the cap replacement.  no hurry here.

enjoy

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1extreme's avatar
1extreme
161 posts
 
@dweller A recent inquiry into the age of an amp, and my concern for the caps, resulted a response "we've tested the caps and they're all good". Is it possible to evaluate the condition of capacitors (other than working or non working)?
Because a capacitor must be removed from the circuit board (at least one end must be de-soldered and lifted) I view such claims as highly suspect. Notice that they never specifically state what tests were performed. Also, realize that an old worn capacitor may test the same as a new high-end capacitor if one is testing for capacitance value only, but the newer capacitor may sound much better.
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