Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

royalmp2001 wrote:
Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

In my experience, in decreasing order of probability:

1. Any non-secure mechanical signal connections, such as relays,
switches, selectors, volume controls, and so on,

2. Semi-permanent connections, like crimp connections,

This takes care of about 95% of most failures I have observed.
And for the age you're talking about:

3. Electrolytic capacitors.

4. Cold solder joints that finally decide to open up

All this assumes the equipment has been used within its
design limits, e.g., no burned or overstressed components
(this assumes componments were selected with sufficient
margin in mind to begin with).

Everything else is VERY low probability of failure. You might have
a pathological case of substrate corrosion in a solid state device,
but that's a manufacturing defect that might just take forever to
appear.

royalmp2001 spake thus:

Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

Not a definitive answer, but a data point: I finally relegated my old
receiver to my computer sound card. It's an Allied (remember Allied
Electronics before they were bought by Tandy?), ca. 1970 that I've owned
for more than 30 years. Not high-end, but a decent mid-line solid state
component. Probably 10-15 watts per channel.

In all that time, I've had to replace exactly one part. Not a power
supply cap as you might expect, but a preamp transistor (in the phono
section) that had gone noisy and microphonic. I got a generic NTE
replacement, and it's as good as new.

But I'd suspect that (big) electrolytics are about the only thing you
should expect to fail. Why would a transformer go bad (unless it was
overdriven)?


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

David Nebenzahl wrote:
royalmp2001 spake thus:

Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?


New lytics and a general cleaning are a good idea, but the problem
with much solid state power-handling gear is the threat of cascade
failures. Other than the above I would just leave it alone.

"royalmp2001" wrote in message
oups.com
Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...

No, the other electrolytics have the shortest life span - there are more of
them, and they are more likely to be umm cost-effective.

followed by what?

Small-signal transistors

The transformer?

If you don't abuse them, transformers are nearly forever.

I want to give my 20yr old Adcom hifi amp (still working)
a new lease of life, and wondered what components I
should replace? Thanks folks

The best policy is to do some bench testing, and then proceed accordingly.
If the machine meets factory specs, invoke the rule about "If its not
broke...".

Arny Krueger wrote:

"royalmp2001" wrote in message
oups.com

Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...


No, the other electrolytics have the shortest life span - there are more of
them, and they are more likely to be umm cost-effective.


followed by what?


Small-signal transistors

Um, would you care to explain the failure mechanism for that statement?

Bob


The transformer?


If you don't abuse them, transformers are nearly forever.


I want to give my 20yr old Adcom hifi amp (still working)
a new lease of life, and wondered what components I
should replace? Thanks folks


The best policy is to do some bench testing, and then proceed accordingly.
If the machine meets factory specs, invoke the rule about "If its not
broke...".



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"royalmp2001" wrote in message
oups.com...
Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

The display lamps!

I have a 1960 Sears Silvertone AM/FM Radio (tubes), the guts from a Magnavox
1968 stereo console (solid state) and a 1977 (?) Sansui 7070 receiver. Other
than some new tubes, probably 30 years ago in the Sears, none of this
equipment has needed any new parts.

I've replaced lytic caps in a mid 1970's radio (15 years ago) and output
components in newer receivers.

I suppose it boils down to the quality of the components used and the design
of the equipment. Also user care and natural events.

While we're at it, can someone educate me on the failure modes of old
lytics? Do they really dry out? I take it the capacitor in my old Sears
radio must have a good seal. I've heard that electrolytic caps can go bad
from non use? How can this be?

Thanks

"royalmp2001" wrote in message
oups.com...
Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

My 34 year old Heathkit AA-1214, which is still in daily operation in my
office, but was the central part of my primary sound system all through high
school and college, and about 15 years after that still has the original
main filter caps. What did fail were a couple of output transistors (at two
years old and again at 35). I replaced all four of them the second time with
the same type part but with the "C" suffix, having a higher breakdown
voltage rating. At age 25 I replaced the "bootstrap" caps in the power
amplifier, which had popped their seals. That's it.

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

You (or someone you know) would need a signal generator and a distortion
analyzer, audio voltmeter and dummy loads to determine if it is still in
spec. If it is, I'd leave it alone.

While we're at it, can someone educate me on the failure modes of old
lytics? Do they really dry out? I take it the capacitor in my old Sears
radio must have a good seal. I've heard that electrolytic caps can go bad
from non use? How can this be?

I have heard this also, but it might be urban legend. I could speculate that
the electrolyte could corrode the cap from the inside, causing leaks. If you
keep it polarized, it would tend to "plate" the can with the aluminum oxide
that is used as the dielectric, protecting it.

However... heat is an enemy of electrolytics, and it might be a race to see
whether heating from ripple current could destroy the cap in use before
corrosion would on the shelf.

My 34 year old Heathkit AA-1214, which is still in daily operation in my
office, but was the central part of my primary sound system all through
high school and college, and about 15 years after that still has the
original main filter caps. What did fail were a couple of output
transistors (at two years old and again at 35). I replaced all four of
them the second time with the same type part but with the "C" suffix,
having a higher breakdown voltage rating. At age 25 I replaced the
"bootstrap" caps in the power amplifier, which had popped their seals.
That's it.

Correction: the transistors popped the second time at T+33 years.

"Karl Uppiano" wrote in message
news:VlU6g.105$W83.89@trnddc07...
While we're at it, can someone educate me on the failure modes of old
lytics? Do they really dry out? I take it the capacitor in my old Sears
radio must have a good seal. I've heard that electrolytic caps can go bad
from non use? How can this be?

I have heard this also, but it might be urban legend. I could speculate
that the electrolyte could corrode the cap from the inside, causing leaks.
If you keep it polarized, it would tend to "plate" the can with the
aluminum oxide that is used as the dielectric, protecting it.

They lose capacitance when left unused for more than a few months. That's
because they use an electrolytic process to form the insulating medium
inside the capacitor. They regain their capacitance, usually, if carefully
recharged slowly.

David Nebenzahl wrote:

But I'd suspect that (big) electrolytics are about the only thing you
should expect to fail. Why would a transformer go bad (unless it was
overdriven)?

This isn't an answer to the original question, so the OP can rest easy.

Some wirewound type parts do go wrong. Marshall guitar tube amplifiers
had a problem with the output transformers about 20 years ago; nothing
else seemed to fail on them. The first Peavey 3020HTs just about drove
me nuts, with the tweeter crackling in circuit but testing good outside
the box, until I figured out the shunt inductor in the crossover tended
to go intermittently *shorted*.


But given that, and returning to the subject at hand, I'd tend to follow
what Dick says: moving parts first, connectors second, capacitors third.
Everything else is far behind.


Francois.

"(null)"

Marshall guitar tube amplifiers
had a problem with the output transformers about 20 years ago; nothing
else seemed to fail on them.


** Everything fails on Marshalls - primarily the poor, over-worked output
valves !

Output transformers have always been common failures too, been replacing
them regularly since the early 1970s. The more recent versions, which flush
mount on the chassis, both the power and output transformers have proved to
be VERY unreliable. Seems to be due to the use of poor quality, low temp /
voltage grade enamel on the winding wire.

The design of the Marshall output stage is seriously flawed - so that when
overdriven, repetitive spike voltages of up to +/- 5kV appear at the valve
anodes and hence the transformer windings.




....... Phil

"Bob Urz" wrote in message

Arny Krueger wrote:

"royalmp2001" wrote in message
oups.com

Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...


No, the other electrolytics have the shortest life span
- there are more of them, and they are more likely to be
umm cost-effective.
followed by what?

Small-signal transistors

Um, would you care to explain the failure mechanism for
that statement?

AFAIK, the failure mechanisms would be mostly package failure leaking the
ambient atmosphere to the chip and through the passivation, and possibly
partial loss of beta due to occasional use at the voltage limits or beyond.

"JohnR66" wrote in message


While we're at it, can someone educate me on the failure
modes of old lytics? Do they really dry out?

They can.

I take it
the capacitor in my old Sears radio must have a good
seal.

They can

I've heard that electrolytic caps can go bad from
non use? How can this be?

The dielectric is actually a layer of alumnium oxide that can slowly
decompose back into the electrolytic. Biringing them up slowly after a long
rest is said to help reform the oxide layer fast enough to prevent
breakdown.

** The fuse.








....... Phil

"Don Pearce"


** **** off - you ASD ****ed ****WIT !!!





......... Phil

On Sat, 6 May 2006 23:19:06 +1000, "Phil Allison"
wrote:


"Don Pearce"


** **** off - you ASD ****ed ****WIT !!!



Ooooooh! I love it when you're rough! Do it some more, please.

d

--
Pearce Consulting
http://www.pearce.uk.com

Arny Krueger wrote:
"Bob Urz" wrote in message


Arny Krueger wrote:


"royalmp2001" wrote in message
egroups.com


Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...


No, the other electrolytics have the shortest life span
- there are more of them, and they are more likely to be
umm cost-effective.

followed by what?


Small-signal transistors


Um, would you care to explain the failure mechanism for
that statement?


AFAIK, the failure mechanisms would be mostly package failure leaking the
ambient atmosphere to the chip and through the passivation, and possibly
partial loss of beta due to occasional use at the voltage limits or beyond.


And what is your reasoning for thinking this? I have replaced very few
small signal transistors by themselves unless they were part of a
cascade failure or power spike. In the past, i saw a few pioneer units
that had some noisy pre amp transistors. MY theory on those is that they
were degraded from excess heat from the output stage and they were a
poor parts choice from the beginning.

As far as caps go, since the advent of miniature electrolytics, the
manufacturers have put more MFD in a smaller case and cut corners.
In some celebrated cases, used stolen formulas and caused massive
problems in computer motherboards. Its very common in the last ten
years to have the small electrolytics fail. take you pick of the devices
they are in. The old caps were much more reliable than the miniature
crap they make today. I have changed very few large power supply caps in
older units. For the most part they were pretty reliable. WHen they did
rarely fail, it was a smoke and smell show.

When a stereo gets 15+ years old, the number one problem is oxidation
and contaminates on the switches and pots causing intermittent or no
operation. Then bad solder joints on the hot spots. If it had poor parts
from the factory, chances are it would have not survived the scrap pile
to collect pension.......

Bob

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"Bob Urz" wrote in message

Arny Krueger wrote:
"Bob Urz" wrote in message


Arny Krueger wrote:


"royalmp2001" wrote in message
oups.com


Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...


No, the other electrolytics have the shortest life span
- there are more of them, and they are more likely to
be umm cost-effective.

followed by what?


Small-signal transistors


Um, would you care to explain the failure mechanism for
that statement?


AFAIK, the failure mechanisms would be mostly package
failure leaking the ambient atmosphere to the chip and
through the passivation, and possibly partial loss of
beta due to occasional use at the voltage limits or
beyond.
And what is your reasoning for thinking this?

Bad parts that found their way into my junkbox, and the junkboxes of several
of my friends and associates.

Arny Krueger wrote:

"Bob Urz" wrote in message


Arny Krueger wrote:

"Bob Urz" wrote in message



Arny Krueger wrote:



"royalmp2001" wrote in message
glegroups.com



Am I right in thinking the power supply caps probably
have the shortest life span of all the
components...


No, the other electrolytics have the shortest life span
- there are more of them, and they are more likely to
be umm cost-effective.


followed by what?


Small-signal transistors


Um, would you care to explain the failure mechanism for
that statement?


AFAIK, the failure mechanisms would be mostly package
failure leaking the ambient atmosphere to the chip and
through the passivation, and possibly partial loss of
beta due to occasional use at the voltage limits or
beyond.

And what is your reasoning for thinking this?


Bad parts that found their way into my junkbox, and the junkboxes of several
of my friends and associates.



Must be the reason why you call it a "Junk Box"

When i strip out old units for parts, i rarely pull the small signal
transistors anymore. I usually pull the power transistors, drivers,
voltage regulators, large resistors, some higher voltage caps and maybe
rectifiers. With the price of electronics going down, there is a lot
of stuff i saved that i need to scrap. Its too easy to collect.....


Bob

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mc wrote:

They lose capacitance when left unused for more than a few months. That's
because they use an electrolytic process to form the insulating medium
inside the capacitor. They regain their capacitance, usually, if carefully
recharged slowly.


That should be "Years", and the proper term is "Reformed" which means
that the electrolyte has to react with the surface of the aluminum
foil. You have to limit the current to less than a mA, and you should
use a source voltage equal to the surge voltage rating of the
electrolytic.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"Michael A. Terrell" wrote in message
...
mc wrote:

They lose capacitance when left unused for more than a few months.
That's
because they use an electrolytic process to form the insulating medium
inside the capacitor. They regain their capacitance, usually, if
carefully
recharged slowly.


That should be "Years", and the proper term is "Reformed" which means
that the electrolyte has to react with the surface of the aluminum
foil. You have to limit the current to less than a mA, and you should
use a source voltage equal to the surge voltage rating of the
electrolytic.

It's measurable in months, although the re-forming is usually effortless if
the capacitor has gone no more than a few years. Beyond that, as you say,
the capacitor should be re-formed at low current rather than by simply
powering on the original circuit.

In article , David Nebenzahl wrote:
royalmp2001 spake thus:

Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

Not a definitive answer, but a data point: I finally relegated my old
receiver to my computer sound card. It's an Allied (remember Allied
Electronics before they were bought by Tandy?), ca. 1970 that I've owned
for more than 30 years. Not high-end, but a decent mid-line solid state
component. Probably 10-15 watts per channel.

In all that time, I've had to replace exactly one part. Not a power
supply cap as you might expect, but a preamp transistor (in the phono
section) that had gone noisy and microphonic. I got a generic NTE
replacement, and it's as good as new.

But I'd suspect that (big) electrolytics are about the only thing you
should expect to fail. Why would a transformer go bad (unless it was
overdriven)?

No, smaller electrolytic caps fail first, especially the ones subjected
to heat. Tandy does not own Allied Electronics now. Wow,
I probably had the same Allied receiver, hooked up to a pair of Utah
speakers, driven by an AR turntable and a Viking 8 Track recorder.

greg

In article , (GregS) wrote:
In article , David Nebenzahl
wrote:
royalmp2001 spake thus:

Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

Not a definitive answer, but a data point: I finally relegated my old
receiver to my computer sound card. It's an Allied (remember Allied
Electronics before they were bought by Tandy?), ca. 1970 that I've owned
for more than 30 years. Not high-end, but a decent mid-line solid state
component. Probably 10-15 watts per channel.

In all that time, I've had to replace exactly one part. Not a power
supply cap as you might expect, but a preamp transistor (in the phono
section) that had gone noisy and microphonic. I got a generic NTE
replacement, and it's as good as new.

But I'd suspect that (big) electrolytics are about the only thing you
should expect to fail. Why would a transformer go bad (unless it was
overdriven)?

No, smaller electrolytic caps fail first, especially the ones subjected
to heat. Tandy does not own Allied Electronics now. Wow,
I probably had the same Allied receiver, hooked up to a pair of Utah
speakers, driven by an AR turntable and a Viking 8 Track recorder.

In fact, Allied, Newark, MCM, Farnell, are all British companies.

greg

GregS spake thus:

In article ,
David Nebenzahl wrote:

royalmp2001 spake thus:

Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

Not a definitive answer, but a data point: I finally relegated my old
receiver to my computer sound card. It's an Allied (remember Allied
Electronics before they were bought by Tandy?), ca. 1970 that I've owned
for more than 30 years. Not high-end, but a decent mid-line solid state
component. Probably 10-15 watts per channel.

In all that time, I've had to replace exactly one part. Not a power
supply cap as you might expect, but a preamp transistor (in the phono
section) that had gone noisy and microphonic. I got a generic NTE
replacement, and it's as good as new.

But I'd suspect that (big) electrolytics are about the only thing you
should expect to fail. Why would a transformer go bad (unless it was
overdriven)?

No, smaller electrolytic caps fail first, especially the ones subjected
to heat. Tandy does not own Allied Electronics now. Wow,
I probably had the same Allied receiver, hooked up to a pair of Utah
speakers, driven by an AR turntable and a Viking 8 Track recorder.

Since you remember this stuff (polite way of saying you're an old fart,
too), do you know if the Tandy that bought Allied and later became Radio
Shack was the same as the Tandy Leather Co.? I always wondered about that.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

If you really want to mod that Adcom, send it to Musical Concepts for
upgrading. They did mine around 15 years ago & it's still going strong,
driving the woofers of my MartinLogan Ascents. See
www.musicalconcepts.com.

"Bob Urz" wrote in message

Arny Krueger wrote:

"Bob Urz" wrote in message


Arny Krueger wrote:

"Bob Urz" wrote in message



Arny Krueger wrote:



"royalmp2001" wrote in
message
oups.com



Am I right in thinking the power supply caps
probably have the shortest life span of all the
components...


No, the other electrolytics have the shortest life
span - there are more of them, and they are more
likely to be umm cost-effective.


followed by what?


Small-signal transistors


Um, would you care to explain the failure mechanism
for that statement?


AFAIK, the failure mechanisms would be mostly package
failure leaking the ambient atmosphere to the chip and
through the passivation, and possibly partial loss of
beta due to occasional use at the voltage limits or
beyond.

And what is your reasoning for thinking this?


Bad parts that found their way into my junkbox, and the
junkboxes of several of my friends and associates.

Must be the reason why you call it a "Junk Box"

It's how I keep count of busted small parts. It's truely junk never to be
used again.

When i strip out old units for parts, i rarely pull the
small signal transistors anymore. I usually pull the power
transistors, drivers, voltage regulators, large resistors, some higher
voltage
caps and maybe rectifiers. With the price of electronics
going down, there is a lot of stuff i saved that i need to scrap. Its too
easy to
collect.....

By the time I scrap stuff out, its usually so obsolete that it all just goes
out with the trash.

royalmp2001 wrote:
Am I right in thinking the power supply caps probably have the shortest
life span of all the components...followed by what? The transformer?

I want to give my 20yr old Adcom hifi amp (still working) a new lease
of life, and wondered what components I should replace? Thanks folks

The phono jacks on those 1985 Adcom power amps were pure crap. If you
plugged in a tight grabbing cable the jack would literally pull apart
when you unplugged. Leaving the outer cylinder of the jack still stuck
in the cable. Definitely replace those (if its a power amp), dont know
if I'd bother if it has a lot of jacks though. Otherwise those Adcoms
were a great value for the money, nice amps.