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Worn Caps - Symptoms?

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Posted on September 3, 2015 at 08:54:36
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 A friend of mine suggested that I install new caps in my Quad 405 power amp which I've had since purchased new in early 1978. However, so far as I can tell, it still sounds fine, works every time I power it up. It did blow a channel in 1989, after which I had both channels replaced. It's worked well ever since, even with caps that are now 37 years old.

Should I consider my friend's suggestion or follow the old saw, if it ain't broke don't fix it? Thanks.

 

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RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 09:25:30
Mike B.
Audiophile

Posts: 26352
Location: OR
Joined: September 27, 1999
Contributor
  Since: September 1, 1999
 I would at least swap out all the electrolytics. I suspect you will notice a significant change in resolution and low end performance.


 

RE: Worn Caps - ?, posted on September 3, 2015 at 10:20:20
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Yesss! replace those.
It would also be "clever' to renew the rectfier diodes as those Age as well. The New/fresh Caps will likely have a renewed Inrush current that may prove a problem with tired diodes.

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 10:20:23
E-Stat
Audiophile

Posts: 37606
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 In the worst case, oozing of dielectric from the cans. At best, loss of value.

You might want to look into upgrading the amp. There are a number of companies who upgrade the passive components, first generation LM301 op amps and power supply.

Upgrade example

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 11:31:31
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 I did contact Connecticut-based Amplifier Experts. He told me that parts and labor would run about $400. That's if parts are still available.
For much less, I could get a newer amp off ebay (Adcom, Haffler, et al). An audio-video store around here would charge $100 just to look at it. A friend will sell me his Bryston 3B for around $400-$450, cheaper than what you see on ebay for the same product. I have not yet hooked it up for a trial run, but am tempted. Make sense?

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 11:57:46
Mike B.
Audiophile

Posts: 26352
Location: OR
Joined: September 27, 1999
Contributor
  Since: September 1, 1999
 I do my own swaps so sometimes forget the costs associated with doing the job. I would step up to the more recent offerings. If you want to keep the Quad, at least pull the cover and look at the power supply caps. If they are the larger variety, they will have screw terminals. Plus and minus terminals are marked. Don't worry about matching the brand. Just match the voltage and value. Value can be more or a bit less if they match physical space limitations. Good luck.

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 12:12:59
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 Thanks, but I wouldn't know what to look for. What do worn caps look like? Typically, how many caps does a 100w/ch amp have?

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 12:54:33
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 This look like it?

http://www.keith-snook.info/quad-405-2-mods.html

Two caps, about 15 minutes to change them. You could post under vintage, there are a lot DIY'ers, maybe you can find one in your area that will give you a hand.

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 16:12:56
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 I opened the back of the amp and found another piece of backing to remove before I could even see the caps. Said the hell with it, replaced the back and re-hooked the amp. As I said, it still sounds fine to my ears.

What I've decided to do is keep it until and unless it craps out. Then, it's on to another amp.

 

RE: Worn Caps - Symptoms?, posted on September 3, 2015 at 21:49:43
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 worn caps MAY bulge. They'll look overstuffed. or maybe even LEAK an awful goo.

When replacing, voltage and capacity are the first 2 things to look at. ALSO, look at the temp rating of the cap. If the amp in question runs at all warm, get 105c rated caps.
Too much is never enough

 

Small Electrolytics, posted on September 3, 2015 at 22:40:19
djk
Manufacturer

Posts: 6135
Joined: June 17, 2000
 There are a handful of small electrolytics I would replace, even before the main filter caps (which is all that has been mentioned here).

 

RE: Worn Caps - Symptoms?, posted on September 4, 2015 at 03:21:44
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 The amp still runs relatively cool.

 

RE: Small Electrolytics, posted on September 4, 2015 at 03:30:50
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 Based on what I've read here and the price of replacing what should be replaced on aging amps, I'm thinking that the purchase of either a new amp or a used one in good condition might be the best option. Restorations are fine, but when they exceed the cost of a newer product of comparable quality, then it becomes a choice of emotional attachment vs. practicality. The same, of course, can be said of automobiles or any product.

 

RE: Worn Caps - Symptoms?, posted on September 4, 2015 at 11:27:38
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 I HONESTLY do Not know enough to say For Certain. Caps would appear to be one of those things which goes right until 'the end' than fails with little audible warning. Like a car battery, these days, which simply FAILS.
IOW, I don't know that the amp would run any warmer, or cooler, for that matter, than with perfectly NEW caps than with defective or near-failure parts.
When Replacing I'd use the 105c rated ALMOST without exception. A slight extra margin of 'heatroom' at minimal extra cost.

Have you VISUALLY inspected the current caps? If ANY signs of failure, ALL are to be RePlaced immediately.

I can't offhand find the Nelson Pass article or comments on power supply caps. I don't think I'd be wrong is saying in HIS amps, he expects them to go 20 to 30 years without problem.
I'll add that if a piece has been sitting IDLE for an extended period of time, THAT'S a red-flag and you may either have probems with the cap or better still, take it to someone with a VARIAC to 'ramp it up' slowly and give the caps a chance to reform. Caps in Regular Use seem to last longer and 'healthier'.
Too much is never enough

 

RE: Worn Caps - Symptoms?, posted on September 4, 2015 at 13:12:17
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 I play my system several times a week, so there's no issue of caps being idle for long. I can't get to the amp's deep innards to see the caps, at least not without taking the thing apart and risk being unable to put it back together. Not that I'd know what to look for if I did.

 

RE: Small Electrolytics, posted on September 4, 2015 at 13:48:02
djk
Manufacturer

Posts: 6135
Joined: June 17, 2000
 It all depends on the costy of labor, the parts cost is tiny.

Can you solder?

Are you willing to learn?

If no to both you will be shopping.

 

RE: Small Electrolytics, posted on September 4, 2015 at 13:53:46
eleiko2@verizon.net
Audiophile

Posts: 207
Joined: October 4, 2008
 no and no

 

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