Old Caps and Aging Diodes??

[Tunaoue]

Hi All, I'm new to this forum.

Question about older solid state amplifiers:
I have a unit that has lots of brawn, but it's about 20 years old.
To give you a feel, it has:
225W into 8 ohms,
360W into 4 ohms,
720W bridged into 8 ohms.

I was told that the older amps tend to get "soft" after years of use.
Mostly the little capacitors in the output stage (NOT the power supply),
and the output transistors switch a little slower after time.
Result is that the amp looses a little "punch" and detail.

I've seen tube amps revived with a replacement set, and I know sometimes an output transistor will burnout like a light, but not sure what to think about the amp going "soft". I can understand it drifting a little, but because it is solid state it shouldn't drift very much.

Anyone have any knowledge about this?
I guess a good test is to ship it to the factory and have them measure it against the specs.

Thanks in advance.

[poneal]

then I wouldn't fret to much over it. I have a 20 year old amp that still kicks it. The manufacturer stated 100wpc into 8ohms but I took it to a small electronics shop and had them test it and it clipped at 80wpc. Never can trust them specs. I took the cover off mine about a year ago and got some of that iso-bath and sprayed down the pots and board, caps, resistors, etc. Plugged it back in and got scared when it started smelling like electronics but it was fine. Kinda like when you first plugged it in when it was new and it had that smell. Never had a problem with it though and that iso-bath cleaned up the pots very nicely. Just my 0.02c

[Mash]

Tunaoue
Ignore the bogus "advice" that I suspect you got from someone who wants to sell you something. Having you fret that your 20 year-old SS amp could "go soft" sounds like that first step toward "upgrading" you into a new amp. The audio industry, like the auto industry, lives on unneeded repeat sales to existing owners.

It is true that capacitors and diodes, like insulation, will wear out in time but this is true only for electrical items that are "fully stressed" during most, or all, of their operating lives. The diodes in auto alternators are fully stressed much of their operating time because their alternators power headlights and ignitions and recharge starting batteries. Failed diodes are the biggest reason that auto alternators must be replaced. Generators are "rewound" ( the windings are removed and the insulation replaced ) because the generator's insulation will wear out typically when it reaches its 30-year design life. This is because the generator's insulation is stressed to its design voltage in normal operation, a design driven by insulation space limitations forced by internal cooling passages, structural load paths required by the stresses in a rotating generator, and so forth.

Audio gear that is correctly designed will have components such as diodes, caps and transistors that are VERY lowly stressed almost all of the time. Audio gear "loafs" most of the time it is used.... unless the owner wishes to go deaf. [Transistors are, as you surmise, somewhat like lightbulbs in that they work or they have failed.] If you amp has lasted 20 years without a failure it must be properly designed, and as well you must not be abusing it. Put this "concern" out of your mind and spend your inqusitive energy attending live recitals. Live recitals are better than heresay opinions for telling you whether you have any "problems" with your sound system that require correction.

[E-Stat]

I was told that the older amps tend to get "soft" after years of use.
Mostly the little capacitors in the output stage (NOT the power supply),
and the output transistors switch a little slower after time.
Result is that the amp looses a little "punch" and detail.
Ouput caps, yes over a long space of time. Output transistors, no. I have a 23 year old amp that still works great. I doubt that I will need to replace it's Sprague electrolytics for quite a while.

rw