Old SS amps

@invalid 

Of course, although it’s always nice to know that if it does it’s less likely to take your speakers out. In any event, I would definitely recommend a sensible preventative maintenance program. Out of curiosity, which Krell do you have?

Techs who work on high-end gear are scarce, and really good ones are rarer than flying pigs. They (justifiably) command high rates.

The downside of this is that at $100+/hr it doesn’t take long for a repair to become economically unfeasible, or the tech won’t touch it if it’s not straightforward and / or looks like it’s going to take a lot of research time. So there are definite plusses for dedicated audiophiles to learn how to do it for ourselves.

@invalid - KSA-300S are beautiful amps.

If this amp blows again, it’s a 100 lb boat anchor.

@wrm57 

Hopefully it won't blow again, but if it does I'll take it and I'll pay for freight :)

I think @pindac drew an outstanding picture of the larger context in which high-end vintage equipment exists and is sought, appreciated, and kept in good custody by a certain breed of audiophile.

20 year old high-end gear is not "old"... It is better described as nicely broken in.

I would highly recommend such gear to the right person. My system is made up of it.

But those who worry about parts availability and serviceability had best buy new gear, and with it the peace of mind that factory warranty confers upon its buyer until it expires, which comes soon enough - unless you get Bryston gear, which has a 20-year warranty... and is quite good too, by the way.

Well-intentioned but misbegotten advice on the urgent need to recap vintage gear yesterday is all too common.

In the real world, electrolytic caps don’t fail that often. Other cap types don’t fail hardly at all (film, ceramic). Wima caps will probably outlive the cockroaches.

The thing is, in order to properly test a cap you have to desolder it. And if it’s a small cap, once it’s desoldered it’s just as easy to drop a new one in, because a) small value caps tend to go bad more often than large ones, b) they only cost 10 or 20 cents, and c) you’ve already done the labor in order to test the cap anyway.

So you do end up doing a lot of systematic recapping whether you like it or not (I don’t). Old caps being replaced almost invariably test fine. A dead cap will make its presence known.

Anyway, my point was that in my experience I’ve probably seen as many failed ICs and semiconductors as I’ve seen failed electrolytic caps, yet I’ve replaced 10 times as many of the latter vs the former.

A more apt comparison would be, which one is easier to fix, a 69 Chevelle or a 92 Cadillac? Exactly. Same for audio gear

I don’t quite understand cap replacement’s how do you tell when they are bad when I’m still impressed & happy with my systems sound? I’m kind of the mindset that if it works don’t fix it. 

@pjlivengood 

You got it: if the amps work, leave the caps alone.

You may want to have bias current and DC offset checked, however. They tend to drift over time. Elevated bias causes operating temperature to rise, and with it the risk of chronic overheating and thermal damage, which can be quite devastating. As for DC offset, it can potentially damage your speakers, but most amps have protective circuitry that shuts down the outputs before damage occurs.

Ive read that electrolitic capacitors dry up, leak, swell after about 15 to 20 years.

@bikefi10 

That’s mostly an urban legend though. Look at your Carver M400: these amps are notably unreliable due to their tight packaging and, well, Carver - yet the caps in it have lasted 40 years.

How long will a amplifier last if it's stored away in a box? Is there a shelf?

@emergingsoul 

The process by which electrolytic caps self-heal is suspended when not powered. Caps can become severely dried out as a result.

There is no hard expiration date, but any equipment that uses electrolytic caps (not just amps) and has been in storage for a long time should be brought back to life slowly and safely on a variac, as long as it has a linear power supply (SMPS-powered equipment is another story, but few audiophiles own any). The variac process allows caps to reform. Long-stored equipment should never be plugged straight into the wall.

A variac is a variable AC supply. It's quite inexpensive and well-worth buying if you plan on putting any long-stored gear back in service.

@emergingsoul 

Manufacturers of electrolytics usually say shelf life is 2 years but it depends on storage conditions, mainly temperature. It's generally accepted that the rate of electrolyte degradation doubles every 10 C increase. In addition, high humidity causes lead corrosion. Climate-controlled storage is pretty critical.

Personally, I would restart anything that hasn't been turned on in a year on a variac.

Old to some, boat anchors to others, missing the bells and whistles of modern…time spent (hobby) irrelevant, its about the sound quality. The make doesn’t matter if it’s liked and breaks ya fix it new or old.

@1971gto455ho 

+1 That's exactly how I look at it. Giving great gear a new lease on life is worth the while in my opinion. Congrats on refurbishing your PC5002M, these are gorgeous amps!

@emergingsoul sadly there is no variac for wine! 😁

Often manufacturers would glue caps to the PCB. Although you'd like to think they did this for the sake of microphonics, the glue was there to hold the components in place while they were being soldered.

Sometimes with age and heat that glue kind of decomposes and spreads out over the PCB from under the cap. For all the world it looks like the cap is leaking, but it's not, it's just glue. 

Not that glue is necessarily benign: in rare cases it becomes conductive and causes short-circuits.

@drmuso 

Thumbs up from a fellow Classé owner! The David Reich designs were fantastic. I definitely have a pair of DR-3 VHC on my bucket list. 

Happy listening!

@boomerbillone 

What you need is a dim bulb tester, not a gas mask 😂

@ronmen 

As stated above, gear stored for many years should not be plugged into the wall. It needs to be visually inspected and if everything looks ok then it needs to be plugged into a variac and brought up to line voltage progressively over a period of 12 to 24 hours. That lets capacitors reform.

@ronmen 

The idea of the variac is to let dried-out caps reform progressively and spare them the full blast of inrush current while in a compromised state. So going back on the variac at this point is unlikely to make a difference.

Re question 2... a lot happens to electronics in 20 years, both actively used and stored. So... it depends.

That said, I think the compulsive hand-wringing over capacitors (while glossing over everything else) that seems to afflict many in the audiophile community is misguided. A number of potential issues with vintage gear are more important than caps.

@ronmen 

No worries, these are good questions.

I don’t have a strong opinion as to whether an amp used daily for 30 years is more likely to need a recap than one that has sat unused for 20 years because caps will deteriorate in both cases, albeit for different reasons. Personally, I would pick the unused one if it hasn’t been plugged in / turned on yet.

Bias drift is quite common and can raise internal components’ operating temperature to dangerous levels (dangerous for the amp that is) if left uncorrected, causing an amp to slowly cook itself to death in some cases. Cooked PCBs are not salvageable past a certain point of doneness, making the amp essentially unrepairable. Such total loss may be uncommon, but it is still best practice to check bias current and DC offset, and adjust them as needed, every couple of years.

Driver and output transistor failure can have significant negative consequences. Same for power supply failure, depending on an amp’s topology.

Granted, modern amps are equipped with protection circuits that are designed to save speakers from being destroyed by excessive DC offset. But early SS amps raw-dogged it; Phase Linear - known for building 300+ wpc amps in the early 1970s out of automotive electronic-ignition transistors, as well as for being the first known audio-related manifestation of Bob Carver - was affectionately nicknamed Flame Linear 🤣

Regular preventative maintenance is desirable with early SS amps.