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Author Topic: Power amp life expectancy  (Read 5310 times)

John Roberts {JR}

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Re: Power amp life expectancy
« Reply #20 on: June 01, 2017, 10:16:36 am »

His CE4000 is still working, it was his CE2000 that went to Nonfunction Junction.  With that model there are several possibilities but I think your choice of output transistors is a good one.  I don't think the 2k is worth repairing.
+1

amps used for SR get more physical stress, and dubious mains power quality, than sitting in a living room or recording studio. 

Yes, common fault in bipolar power amps is shorted output devices. If you have more time than money you might try fixing (the 2000) yourself but perhaps open it up and take a look around first. IIRC one weakness in that particular re-packaging job was using modest sized SMD emitter degeneration resistors that tend to burn holes in the PCB when the power devices fail short circuit.  :o The design was similar to old DC300 (quasi-complementary) so reasonably reliable but IMO not very hifi. The well respected CE4000 was an entirely different animal, and why they were all in the same one amp series family remains a head scratcher? 

JR

PS: My living room amp that I designed myself back in the early 70s still works, or did last time I turned it on (yawn).
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Jean-Pierre Coetzee

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Re: Power amp life expectancy
« Reply #21 on: June 06, 2017, 05:01:49 pm »

All the research I've done has shown that power cycling equipment is about as bad for them as leaving them on so...
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John Roberts {JR}

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Re: Power amp life expectancy
« Reply #22 on: June 06, 2017, 06:35:58 pm »

All the research I've done has shown that power cycling equipment is about as bad for them as leaving them on so...
Research where?

I have actually thought about this over the years. Some products in the fixed instal market are designed to be turned on and left on...In one wall mount amp I made the cooling fan 3 speed, so when it was resting it could really rest.  8) Moving parts like fans clearly have a life related to hours of operation. Solid state devices not so much. There are mechanical stresses related to thermal cycling (heating up when on, and cooling off when off). Reservoir capacitors over time and temperature can lose electrolyte and degrade. Modern capacitors seem a lot better than they were last century, and we can also specify higher temperature caps for hotter ambient applications.  These are all well understood and manageable factors. One wild card in this "on vs cycled on/off" analysis is quality of the mains power... if rouge power surges occur often, like weather related lightning strikes, maybe off is better.   

I actually wrote about this question for my magazine column back in the 80s. As I recall the light bulb on my desk burned out while I was writing the column.  :o  I don't have any incandescent light bulbs left these days.

JR
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TJ (Tom) Cornish

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Re: Power amp life expectancy
« Reply #23 on: June 07, 2017, 08:33:10 am »

All the research I've done has shown that power cycling equipment is about as bad for them as leaving them on so...
That's not been my experience.
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Ivan Beaver

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Re: Power amp life expectancy
« Reply #24 on: June 07, 2017, 04:02:02 pm »


I actually wrote about this question for my magazine column back in the 80s. As I recall the light bulb on my desk burned out while I was writing the column.  :o  I don't have any incandescent light bulbs left these days.

JR
I don't think I have ever seen an incandescent bulb burn out while it was on.  But I could be wrong-or just lucky-or unlucky. :-\

They always seem to go out when power is first applied and the filaments are cold-pulling extra current through them.

However I have had florescent and LED lights go out while being on.
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Ivan Beaver

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Re: Power amp life expectancy
« Reply #25 on: June 07, 2017, 04:04:45 pm »



PS: My living room amp that I designed myself back in the early 70s still works, or did last time I turned it on (yawn).
The old Peavey mixer under my desk top worked the last time I plugged it in-which was right before I put it under the glass.  That was a couple of years ago.-but still in this decade.
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John Roberts {JR}

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Re: Power amp life expectancy
« Reply #26 on: June 07, 2017, 05:08:06 pm »

I don't think I have ever seen an incandescent bulb burn out while it was on.  But I could be wrong-or just lucky-or unlucky. :-\

They always seem to go out when power is first applied and the filaments are cold-pulling extra current through them.

However I have had florescent and LED lights go out while being on.
Just lucky I guess... ;D Actually that has been my experience too, except for the one time I was writing about exactly that.  ::)

 I thought it was an interesting outlier and I mentioned it in my column (30 years ago). Yes, we almost forget how fragile the incandescent lamps are. Remarkable for what they were, but ancient history now.

JR
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Bob Leonard

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Re: Power amp life expectancy
« Reply #27 on: June 07, 2017, 05:20:59 pm »

I really wish people would stop stating that the "capacitors" in an amplifier are usually what fails. Quality caps almost never fail without a related failure in another component. Electrolytic capacitors dry out with age, but you're usually talking about 10-15 years, and failing electrolytic capacitors will always show an outward sign of failure, i.e. bubbling, swelling, exploding. Caps that are not polarized, Mylar, ceramic, orange drop, etc. will last many more years than a polarized electrolytic, however, they can be easily checked by lifting the grounded leg and checking voltage. There should be no B+.

Anyway, all of the components should be metered and checked starting with the power supply and the caps associated. Then, if the voltage(s) is/are correct and no voltage is passing in the wrong direction it's time to trace further. Good checks mean less wrecks.   
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John Roberts {JR}

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Re: Power amp life expectancy
« Reply #28 on: June 07, 2017, 06:00:05 pm »

I really wish people would stop stating that the "capacitors" in an amplifier are usually what fails.
Who said that?
Quote

Quality caps almost never fail without a related failure in another component.
a shorted diode can cook a cap faster than squat... Elevated ambient temperature (like inside a power amp) can speed up deterioration.
Quote
Electrolytic capacitors dry out with age, but you're usually talking about 10-15 years,
OP is asking about an amp that old...
Quote
and failing electrolytic capacitors will always show an outward sign of failure, i.e. bubbling, swelling, exploding.
How about leaking ? (like from their "bung hole"... actually a pressure relief vent in the rubber bung).
Quote
Caps that are not polarized, Mylar, ceramic, orange drop, etc. will last many more years than a polarized electrolytic, however, they can be easily checked by lifting the grounded leg and checking voltage. There should be no B+.

Anyway, all of the components should be metered and checked starting with the power supply and the caps associated. Then, if the voltage(s) is/are correct and no voltage is passing in the wrong direction it's time to trace further. Good checks mean less wrecks.

In (solid state) power amps the output devices are the most likely suspects (fail short circuit). But anybody spending enough time in the trenches will see many different components fail.

JR
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Ivan Beaver

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Re: Power amp life expectancy
« Reply #29 on: June 07, 2017, 07:01:47 pm »

I really wish people would stop stating that the "capacitors" in an amplifier are usually what fails.
Totally agreed.

I was a bench tech for many many years.

With the exception of some old (60s) fender amps, and tantalum caps, a capacitor failure is almost non existent.

Yes I have replace a few, but not enough to even worry about-in my opinion.

I think in most cases, the people saying it are just passing it along trying "be smart" because they heard some tech mention it and it sounds cool.

Agreed the JR, the output devices are BY FAR the biggest failure point in amplifiers.

Guess what-they are the things that are working the hardest also.
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