Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Yahama Stagepas-300

After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)
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Stephen Birchall wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)

+++++++

I'm surprised they were loose. 2 ounces each and 2 screws each, and both
amps failing at the same time? or continued using with one amp only until
that failed?
Perhaps a resonance thing , one style of music , resonating with the amp
subunits

A lot of engineers are scared to even look inside these tiny class D , SMPS
, antiphase output amps and probably give a "****-off" quote


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"Nutcase Kook"


A lot of engineers are scared to even look inside these tiny class D ,
SMPS
, antiphase output amps and probably give a "****-off" quote


** A repair tech I know calls doing that " Blowing it out of the Water ".



...... Phil


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"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)



Last one I had in with a blown power amp module, (couple of years ago now) I
just got another module from Yamaha.
Charge to the customer for the part was £75.

That quote contains rather a lot of labour then.



Cheers,

Gareth.


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Default Yahama Stagepas-300



"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built in
brush. It dries very quickly, and will proof the screw or nut against coming
loose by vibration, whilst still allowing for an easy 'break' of the seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa



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Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a

dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built in
brush. It dries very quickly, and will proof the screw or nut against

coming
loose by vibration, whilst still allowing for an easy 'break' of the seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin brush
to apply it. Would be nice to know from the OP whether the screws just undid
or is the plastic thread part stripped ? ie larger screws needed, even if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to component-level
repair


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"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a

dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built in
brush. It dries very quickly, and will proof the screw or nut against

coming
loose by vibration, whilst still allowing for an easy 'break' of the seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws just
undid
or is the plastic thread part stripped ? ie larger screws needed, even if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to component-level
repair




The £75 included a reasonably healthy mark up to the price I paid, which was
probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of all new
parts, and I figure the extra few quid on top of the labour and parts I
would have charged for component level repair was in the customer's best
interests.

Plus it would not come back like a boomerang covered in dingo poo, costing
me time and reputation.



Cheers,


Gareth.


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"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a

dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built
in
brush. It dries very quickly, and will proof the screw or nut against

coming
loose by vibration, whilst still allowing for an easy 'break' of the
seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws just
undid
or is the plastic thread part stripped ? ie larger screws needed, even if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to component-level
repair




The £75 included a reasonably healthy mark up to the price I paid, which
was probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of all
new parts, and I figure the extra few quid on top of the labour and parts
I would have charged for component level repair was in the customer's best
interests.

Plus it would not come back like a boomerang covered in dingo poo, costing
me time and reputation.



Cheers,


Gareth.


Ah, but is a new board *actually* more reliable than an old one properly
repaired ? I've just been having this argument with one of my customers.
Bathtub curves etc would suggest not ... :-)

Arfa

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"Arfa Daily"
"Gareth Magennis"

My judgment, in this case, was to go for the ultimate reliability of all
new parts, and I figure the extra few quid on top of the labour and parts
I would have charged for component level repair was in the customer's
best interests.

Plus it would not come back like a boomerang covered in dingo poo,
costing me time and reputation.


Ah, but is a new board *actually* more reliable than an old one properly
repaired ? I've just been having this argument with one of my customers.
Bathtub curves etc would suggest not ... :-)



** If a repairer installs a major PCB then he (or she) becomes responsible
for the whole damn thing.

Not just their repair work and parts used.

Ya gotta be REAL sure there are no inherent issues with the product and the
new and probably expensive PCB is not at all likely to be either DOA or go
faulty on the bench.

I hate buying PCBs for this reason and the same goes for speakers in combo
amps too.

I make the customer buy the damn things and take all risk.


.... Phil






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"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a
dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built
in
brush. It dries very quickly, and will proof the screw or nut against
coming
loose by vibration, whilst still allowing for an easy 'break' of the
seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws just
undid
or is the plastic thread part stripped ? ie larger screws needed, even
if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to component-level
repair




The £75 included a reasonably healthy mark up to the price I paid, which
was probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of all
new parts, and I figure the extra few quid on top of the labour and parts
I would have charged for component level repair was in the customer's
best interests.

Plus it would not come back like a boomerang covered in dingo poo,
costing me time and reputation.



Cheers,


Gareth.


Ah, but is a new board *actually* more reliable than an old one properly
repaired ? I've just been having this argument with one of my customers.
Bathtub curves etc would suggest not ... :-)

Arfa




Dunno, but one that has had a catastophic failure at high power may well
have damaged or weakened components that may fail some time later.

You would have to specifically conduct a proper test of blown up Yamaha
Power Amp Modules, and see whether repaired ones do, or do not, last longer
than a new original. And of course it would depend who has repaired it.
This is not a typical type of PCB or circuitry, its a bit of a special.

I doubt very much that data is out there, so you pays your money and takes
your choice!


Cheers,


Gareth.









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Posts: 5,247
Default Yahama Stagepas-300

Gareth Magennis wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message

...
After reading all of the issues regarding the aforementioned mixer,

I
decided I had nothing to loose by taking it to pieces and

attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by

crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is

sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost

approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a
dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own

built
in
brush. It dries very quickly, and will proof the screw or nut against
coming
loose by vibration, whilst still allowing for an easy 'break' of the
seal
with a screwdriver. Also good for sealing preset pots against

vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws just
undid
or is the plastic thread part stripped ? ie larger screws needed, even
if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to

component-level
repair




The £75 included a reasonably healthy mark up to the price I paid,

which
was probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of

all
new parts, and I figure the extra few quid on top of the labour and

parts
I would have charged for component level repair was in the customer's
best interests.

Plus it would not come back like a boomerang covered in dingo poo,
costing me time and reputation.



Cheers,


Gareth.


Ah, but is a new board *actually* more reliable than an old one properly
repaired ? I've just been having this argument with one of my customers.
Bathtub curves etc would suggest not ... :-)

Arfa




Dunno, but one that has had a catastophic failure at high power may well
have damaged or weakened components that may fail some time later.

You would have to specifically conduct a proper test of blown up Yamaha
Power Amp Modules, and see whether repaired ones do, or do not, last

longer
than a new original. And of course it would depend who has repaired it.
This is not a typical type of PCB or circuitry, its a bit of a special.

I doubt very much that data is out there, so you pays your money and takes
your choice!


Cheers,


Gareth.









I can only go by personal anecdote. One amp repaired with cheap generic
Mosfets and generic fuseable resistors and returned a year later with no
problem with that amp but the other original one blown . I had improved the
air circulation through the whole amp but the cause of the second failure
was a shorted very basic 22uF/50V cap knocking out a FET and fuseR ,
likewise replaced with a generic FET and R and bigger cap
I've yet to see a problem with the ps of these amps


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Posts: 818
Default Yahama Stagepas-300


"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message

...
After reading all of the issues regarding the aforementioned
mixer,

I
decided I had nothing to loose by taking it to pieces and

attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by

crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is

sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost

approx
£250 to fix because on his inspection, one of the channels had
been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put
a
dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own

built
in
brush. It dries very quickly, and will proof the screw or nut
against
coming
loose by vibration, whilst still allowing for an easy 'break' of the
seal
with a screwdriver. Also good for sealing preset pots against

vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws
just
undid
or is the plastic thread part stripped ? ie larger screws needed,
even
if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to

component-level
repair




The £75 included a reasonably healthy mark up to the price I paid,

which
was probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or
less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of

all
new parts, and I figure the extra few quid on top of the labour and

parts
I would have charged for component level repair was in the customer's
best interests.

Plus it would not come back like a boomerang covered in dingo poo,
costing me time and reputation.



Cheers,


Gareth.


Ah, but is a new board *actually* more reliable than an old one
properly
repaired ? I've just been having this argument with one of my
customers.
Bathtub curves etc would suggest not ... :-)

Arfa




Dunno, but one that has had a catastophic failure at high power may well
have damaged or weakened components that may fail some time later.

You would have to specifically conduct a proper test of blown up Yamaha
Power Amp Modules, and see whether repaired ones do, or do not, last

longer
than a new original. And of course it would depend who has repaired it.
This is not a typical type of PCB or circuitry, its a bit of a special.

I doubt very much that data is out there, so you pays your money and
takes
your choice!


Cheers,


Gareth.









I can only go by personal anecdote. One amp repaired with cheap generic
Mosfets and generic fuseable resistors and returned a year later with no
problem with that amp but the other original one blown . I had improved
the
air circulation through the whole amp but the cause of the second failure
was a shorted very basic 22uF/50V cap knocking out a FET and fuseR ,
likewise replaced with a generic FET and R and bigger cap
I've yet to see a problem with the ps of these amps




That's the problem really- statistically a sample size of 1 is not very
meaningful.

The lack of ps problems, however, is slightly more meaningful. I haven't
seen any either.



Cheers,


Gareth.


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Gareth Magennis wrote in message
...

"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message

...






That's the problem really- statistically a sample size of 1 is not very
meaningful.

The lack of ps problems, however, is slightly more meaningful. I haven't
seen any either.



Cheers,


Gareth.



I have assumed the problems stem from heat build up. The last one , that
exploded small cap, was sandwiched between the output filter choke and the
main Al heatsink that runs the length of the amp units. So not only next to
a heated surface, 85 deg C rated, its own body is blocking the air path to a
large extent. This was after the previous repairing where I now always lift
and prop up the outlet vent and drill open up the line of inlet holes, under
the handle at the other end of the amp casing.
Another one the owner reported feeling the outlet air and noting it was
hotter than normal.
The next one i see, I'll check the airpath over the ps, probably less
cluttered


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Posts: 6,772
Default Yahama Stagepas-300



"Gareth Magennis" wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer,
I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by
crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is
sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a
dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built
in
brush. It dries very quickly, and will proof the screw or nut against
coming
loose by vibration, whilst still allowing for an easy 'break' of the
seal
with a screwdriver. Also good for sealing preset pots against
vibration
movement, or tamper-proofing them.

Arfa


Thats what I use on these Stagepas amp subunits, requires a long thin
brush
to apply it. Would be nice to know from the OP whether the screws just
undid
or is the plastic thread part stripped ? ie larger screws needed, even
if
length is cut down, to give bite

As for 75 squid from Yamaha just shows the advantage to component-level
repair




The £75 included a reasonably healthy mark up to the price I paid, which
was probably around £55.

You have to judge whether, if you did repair to component level, the
customer would pay more or less for your services, and how more or less
reliable this module would subsequently be.

My judgment, in this case, was to go for the ultimate reliability of all
new parts, and I figure the extra few quid on top of the labour and
parts I would have charged for component level repair was in the
customer's best interests.

Plus it would not come back like a boomerang covered in dingo poo,
costing me time and reputation.



Cheers,


Gareth.


Ah, but is a new board *actually* more reliable than an old one properly
repaired ? I've just been having this argument with one of my customers.
Bathtub curves etc would suggest not ... :-)

Arfa




Dunno, but one that has had a catastophic failure at high power may well
have damaged or weakened components that may fail some time later.

You would have to specifically conduct a proper test of blown up Yamaha
Power Amp Modules, and see whether repaired ones do, or do not, last
longer than a new original. And of course it would depend who has
repaired it.
This is not a typical type of PCB or circuitry, its a bit of a special.

I doubt very much that data is out there, so you pays your money and takes
your choice!


Cheers,


Gareth.


Actually, in the case of these dreadful little amps, I am with you, and I
think that a replacement board is the way to go when there has been a
catastrophic failure. My recent experience involved a main board from a
vending machine. I had been asked by a customer that I repair a lot of other
modules for, to look into repairing these items, and a number of faulty ones
had been sent to me for evaluation. I had spent some time on the project
studying the very limited service information for the machine, to work out
what all the considerable number of inputs and outputs were for, and how to
load and stimulate these to fool a board into thinking that it was installed
in a working machine. I had already established that at least half of the
boards that had been sent for evaluation, had a single failed triac on them,
so they would potentially have been a nice little earner.

Then, all of a sudden, the customer comes back to me, and says that the
project has been called off, because their customer, who has a very great
deal of these machines installed in their premises, wants only brand new
boards as replacements, and is not prepared to accept boards that have been
repaired. I asked why this was, and the answer that I got was that they felt
that new boards would be more reliable. No matter how much that I pointed
out that the real life evidence of bathtub curves and infant mortality,
clearly refuted that premise, they were not having any of it. They seemed
unable to understand that a board that has been in service for a while has
passed the infant mortality stage, and is fully burnt in. And that it is in
the main phase of its service life, where any problems are likely to be
random single component failures. None of the parts on this board were
specials, so it could have been repaired to full manufacturer's spec, using
original manufacturer's parts. In fact, the triac that seemed to be failing
could actually have been upgraded to the next one in the series to *improve*
overall reliability.

But here's the really silly bit. Another board in the machine, which I
already repair for them, suffers a faulty tactile switch on a regular basis.
So I asked if they were going to stop having that repaired as well. Oh no,
they said. We can carry on doing that one, because it's only a replacement
switch. Slowly banging my head on the bench, I asked them why they felt that
replacing that single switch was any different from replacing a single
triac, and how they felt that a board that was repaired by having that
switch put in, would be any more reliable than a board that had been
repaired by having a triac put in it. There was no answer, because they
really couldn't see the logic ...

To be fair, the guy that I deal with direct, was with me on this, but his
hands were tied from further up the food chain. What bothers me most is what
happens to all of the faulty boards. Do they just become scrap destined for
landfill ? Bit of a waste ...

Arfa

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On Thu, 19 Jan 2012 01:50:54 -0000, "Arfa Daily"
wrote:



"Stephen Birchall" wrote in message
...
After reading all of the issues regarding the aforementioned mixer, I
decided I had nothing to loose by taking it to pieces and attempting
to test the power output stage. On dismantling all of the plug in
units, it became apparent that both of the output boards had come
loose either by shock or vibration despite being held in by crosshead
screws. After testing the transistors, which were OK, I plugged
everything back in a couple of times to clean the contacts and hey
presto, I now have a fully functioning unit again. So it is sometimes
best to try the simple things first, before spending a fortune.
(previously an electronics engineer had told me it would cost approx
£250 to fix because on his inspection, one of the channels had been
fried. I shan't be recommending him to anyone!)


Nail polish is very good for stopping screws coming loose. Just put a dollop
around the head of the screw, and onto the surface that it's screwed
against. Very convenient as it is in a small bottle with its own built in
brush. It dries very quickly, and will proof the screw or nut against coming
loose by vibration, whilst still allowing for an easy 'break' of the seal
with a screwdriver. Also good for sealing preset pots against vibration
movement, or tamper-proofing them.

Arfa


Yep works just fine, been doing it for 50 years.

?-)


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"Arfa Daily"

Then, all of a sudden, the customer comes back to me, and says that the
project has been called off, because their customer, who has a very great
deal of these machines installed in their premises, wants only brand new
boards as replacements, and is not prepared to accept boards that have
been repaired. I asked why this was, and the answer that I got was that
they felt that new boards would be more reliable. No matter how much that
I pointed out that the real life evidence of bathtub curves and infant
mortality, clearly refuted that premise, they were not having any of it.
They seemed unable to understand that a board that has been in service for
a while has passed the infant mortality stage, and is fully burnt in. And
that it is in the main phase of its service life, where any problems are
likely to be random single component failures. None of the parts on this
board were specials, so it could have been repaired to full manufacturer's
spec, using original manufacturer's parts. In fact, the triac that seemed
to be failing could actually have been upgraded to the next one in the
series to *improve* overall reliability.



** You has to supply and therefore warranty the new PCBs ??

Not * YOU * I hope.

I would make the customer purchase all such boards and then you have no
warranty obligation over them.



.... Phil




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Arfa Daily wrote in message
...


"Gareth Magennis" wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message




No matter how much that I pointed
out that the real life evidence of bathtub curves and infant mortality,
clearly refuted that premise, they were not having any of it. They seemed
unable to understand that a board that has been in service for a while has
passed the infant mortality stage, and is fully burnt in. And that it is

in
the main phase of its service life, where any problems are likely to be
random single component failures. None of the parts on this board were
specials, so it could have been repaired to full manufacturer's spec,

using
original manufacturer's parts. In fact, the triac that seemed to be

failing
could actually have been upgraded to the next one in the series to

*improve*
overall reliability.

But here's the really silly bit. Another board in the machine, which I
already repair for them, suffers a faulty tactile switch on a regular

basis.
So I asked if they were going to stop having that repaired as well. Oh no,
they said. We can carry on doing that one, because it's only a replacement
switch. Slowly banging my head on the bench, I asked them why they felt

that
replacing that single switch was any different from replacing a single
triac, and how they felt that a board that was repaired by having that
switch put in, would be any more reliable than a board that had been
repaired by having a triac put in it. There was no answer, because they
really couldn't see the logic ...

To be fair, the guy that I deal with direct, was with me on this, but his
hands were tied from further up the food chain. What bothers me most is

what
happens to all of the faulty boards. Do they just become scrap destined

for
landfill ? Bit of a waste ...

Arfa



I've come across the concept of failure-rate variability over time etc but I
think the term of a bathtub plot is new to me.
Joins the hockeystick, J, bell, and dead-cat bounce


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"Phil Allison" wrote in message
...

"Arfa Daily"

Then, all of a sudden, the customer comes back to me, and says that the
project has been called off, because their customer, who has a very great
deal of these machines installed in their premises, wants only brand new
boards as replacements, and is not prepared to accept boards that have
been repaired. I asked why this was, and the answer that I got was that
they felt that new boards would be more reliable. No matter how much that
I pointed out that the real life evidence of bathtub curves and infant
mortality, clearly refuted that premise, they were not having any of it.
They seemed unable to understand that a board that has been in service
for a while has passed the infant mortality stage, and is fully burnt in.
And that it is in the main phase of its service life, where any problems
are likely to be random single component failures. None of the parts on
this board were specials, so it could have been repaired to full
manufacturer's spec, using original manufacturer's parts. In fact, the
triac that seemed to be failing could actually have been upgraded to the
next one in the series to *improve* overall reliability.



** You has to supply and therefore warranty the new PCBs ??

Not * YOU * I hope.

I would make the customer purchase all such boards and then you have no
warranty obligation over them.



... Phil



No, I don't have to supply the boards. The whole maintenance operation is
their baby. They were just going to get me to repair the faulty boards that
their engineers swap out in the field, as I already do for many of the other
vending products that they sell and service. I guess they were trying to
save themselves some money over their current practice of buying new
replacement boards from the machine manufacturer. Their customer that uses
the machines in question, is a huge corporate outfit, so I'm willing to bet
that they have a fixed price contract that covers the supply and rental of
the machines with maintenance thrown in. I would further guess that someone
at the supply / maintenance company, who is my customer, worked out that
they could make a lot more money, or better cover their costs, by having me
repair the boards at £xx per board, rather than buying new ones at £4xx per
board, and binning the faulty ones. And then somehow, their customer found
out about their intentions ... :-(

Arfa

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"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Gareth Magennis" wrote in message
...

"Arfa Daily" wrote in message
...


"Gareth Magennis" wrote in message
...

"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"Stephen Birchall" wrote in message




No matter how much that I pointed
out that the real life evidence of bathtub curves and infant mortality,
clearly refuted that premise, they were not having any of it. They seemed
unable to understand that a board that has been in service for a while
has
passed the infant mortality stage, and is fully burnt in. And that it is

in
the main phase of its service life, where any problems are likely to be
random single component failures. None of the parts on this board were
specials, so it could have been repaired to full manufacturer's spec,

using
original manufacturer's parts. In fact, the triac that seemed to be

failing
could actually have been upgraded to the next one in the series to

*improve*
overall reliability.

But here's the really silly bit. Another board in the machine, which I
already repair for them, suffers a faulty tactile switch on a regular

basis.
So I asked if they were going to stop having that repaired as well. Oh
no,
they said. We can carry on doing that one, because it's only a
replacement
switch. Slowly banging my head on the bench, I asked them why they felt

that
replacing that single switch was any different from replacing a single
triac, and how they felt that a board that was repaired by having that
switch put in, would be any more reliable than a board that had been
repaired by having a triac put in it. There was no answer, because they
really couldn't see the logic ...

To be fair, the guy that I deal with direct, was with me on this, but his
hands were tied from further up the food chain. What bothers me most is

what
happens to all of the faulty boards. Do they just become scrap destined

for
landfill ? Bit of a waste ...

Arfa



I've come across the concept of failure-rate variability over time etc but
I
think the term of a bathtub plot is new to me.
Joins the hockeystick, J, bell, and dead-cat bounce




Well, I don't know about that. I was taught it at college over 40 years ago,
so it's not some new fangled concept. If you put the term into Google, you
will get many thousands of hits on the subject, including modern
interpretations.

Arfa

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On Sat, 21 Jan 2012 12:34:13 -0000, "N_Cook" wrote:

snip

replacing that single switch was any different from replacing a single
triac, and how they felt that a board that was repaired by having that
switch put in, would be any more reliable than a board that had been
repaired by having a triac put in it. There was no answer, because they
really couldn't see the logic ...

To be fair, the guy that I deal with direct, was with me on this, but his
hands were tied from further up the food chain. What bothers me most is

what
happens to all of the faulty boards. Do they just become scrap destined

for
landfill ? Bit of a waste ...

Arfa



I've come across the concept of failure-rate variability over time etc but I
think the term of a bathtub plot is new to me.
Joins the hockeystick, J, bell, and dead-cat bounce

The bathtub curve has been around for a long time. Some about WW2 era
military reliability books were filled with it. It is still present in
Military reliability calculations.

I got see an interesting example of management think about reliability
some decades ago. There was this high energy density capacitor (at the
time) some 40 uF at 2 kV in a 1" diameter, 4" long package, not
electrolytic! In characterization testing it had about a 400 hour in use
life, it also had something like a 40 percent failure rate in the first 10
to 20 hours. The management started insisting on 168 hours 100 percent
burn in regimen and could not understand why they could not achieve 250
hour operational life. Nobody could convince them, even with test data,
that a 24 hour burn in would give them the 250 hour operational life.

Some Managers.

?-)
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