Main filter caps - to replace or not?

[techguy0192]

I dropped off my MC752 with one of the top McIntosh techs in Atlanta a couple of weeks ago. The amp was working perfectly; however, I felt it was time for it's 30 year checkup. I'm pleased to report that this 100% original 30 year old amp made 91 watts per channel.

He will be installing fresh caps on the driver boards and new LED lamps. He said the main filter caps tested perfectly fine, it was up to me on if I want to replace them or not. The extra cost of the parts is not a big deal. I'm looking at it from the angle of the main filter caps being 30 years old and does it makes sense to just go ahead and take care of them while he's in the amp. They would obviously be replaced with the caps of equally or better quality with the same values of the originals. He's not sure if he can get new caps in the same color. A concerns on that is if i ever sell the amp, how many buyer would notice that and possibly be turned off. I could probably get the caps from McIntosh with the logos, which would put any fears a future buyer might have to rest. Maybe I'm making too big a deal out of this. What's everyone's thought on this? Quality replacement.....order them from McIntosh....keep the originals?

Looking forward to having that little powerhouse of an amp back!

 

[c_dk]

How much power is it making under real stress at 20 Hz? If it passes that stress test I let the old ones stay in use until they no longer meet the challenge.

 

[kevzep]

How did he test the caps? Most people are just using these hand held meters and checking for ESR, I prefer to use a proper old style capacitor checker which will operate the cap at its rated voltage and check for leakage on its limit, many 30 year old caps will not pass this test, but will pass on a hand held meter.
If the cost doesn't bother you, and the tech has the correct caps to fit, then I would do it.

 

[techguy0192]

How much power is it making under real stress at 20 Hz? If it passes that stress test I let the old ones stay in use until they no longer meet the challenge.

The information I have is based on a brief 10 minute phone conversation. I'd don't know all the details. He did test the caps individually for leaks and said they were healthy. I'm fairly certain he would have done a 20Hz and 20KHz power test. I should have asked, but like I said it was just a brief call to see if any major issues were found. The best information I have to go on, without the detailed output specs, was the advise that new caps *might* help with the bottom end performance.

 

[Searing75]

Just have him replace them. Piece of mind. Don't have to revisit in 5 years. Maybe the placebo effect of thinking it sounds better will occur, and you'll be happier. Then again, maybe it really will tighten things up.

 

[CohibaJoe]

Just have him replace them. Piece of mind. Don't have to revisit in 5 years. Maybe the placebo effect of thinking it sounds better will occur, and you'll be happier. Then again, maybe it really will tighten things up.

Yep...I do and would make it a Complete Cap Job.

 

[BillWojo]

Replace them, it seems that a lot of parts are slowly being discontinued and 5 or 10 years from now they may be no longer available. Big linear power supply's seem to be disappearing and being replaced with switching supply's in all manner of equipment. They don't use the massive capacitors that linear supply's use. As demand dwindles we may find that it gets harder and harder to find caps in the sizes that we need.

BillWojo

 

[cduarte]

Replace them, it seems that a lot of parts are slowly being discontinued and 5 or 10 years from now they may be no longer available. Big linear power supply's seem to be disappearing and being replaced with switching supply's in all manner of equipment. They don't use the massive capacitors that linear supply's use. As demand dwindles we may find that it gets harder and harder to find caps in the sizes that we need.

BillWojo

while that may be true, I had no issues at all finding capacitors for any of my McIntosh rebuilds, including my mc2300 which has enormous filter capacitors, 6 of them which are over 50,000uf apiece and the same size as the original 33,000uf caps.

 

[BillWojo]

No issues now but what about 10 or 20 years from now. Linear power supplies are not the norm anymore. Switch mode PS use much smaller caps. Do you really think the major cap manufactures want to change tooling out for a product that they may sell only a few dozen or hundred's a year? I can see a day when the selection gets mighty thin.
For something like Mac gear, it's in the your best interest to replace any components that age or wear while they are still available.

BillWojo

 

[kevzep]

No issues now but what about 10 or 20 years from now. Linear power supplies are not the norm anymore. Switch mode PS use much smaller caps. Do you really think the major cap manufactures want to change tooling out for a product that they may sell only a few dozen or hundred's a year? I can see a day when the selection gets mighty thin.
For something like Mac gear, it's in the your best interest to replace any components that age or wear while they are still available.

BillWojo

I was thinking exactly the same thing, this is a very good point.....

 

[damacman]

I was thinking exactly the same thing, this is a very good point.....

By then, carbon super caps will be the norm.