Basically, there was a severe buzzing noise on the output and the
fault was traced to the PSU supply not being stable.

Is it a linear, or switch-mode? How many output rails are there? does the
instability affect them all, or only one or two?

The caps were
replaced

All of them?

and the problem was rectified. Well, within a couple of
months the fault is back,

So probably not capacitors then, unless it's the ones that got missed last
time. (Is the fault *exactly* the same?) Maybe the instability is the
result of a broken PCB track, dry joint or poor connection somewhere that
makes contact when it wants too, and the "cure" last time was due to the
physical handling of the PSU causing this to make contact again, for a
while.

and instead of paying silly prices to one of
the very few tape machine repair guys around, my mate wanted me to fix
it if I could find the faulty caps. The last repair cost £500. The
tape machine is a Saturn Soundcraft, and aparently there is only one
person in the country who can repair them (he lives in Bury St.
Edmunds).

Unlikely. Unless the machine was designed on Saturn (or in Bury St Ed) any
competent repair technician ought to be able repair it.

Excatly what I thought.
Mind you they do a very good line of condensers on the planet Metaluna.
http://en.wikipedia.org/wiki/This_Island_Earth

--
Graham.

%Profound_observation%

"David Looser" wrote in message
...
"Marky P" wrote in message
...

Basically, there was a severe buzzing noise on the output and the
fault was traced to the PSU supply not being stable.

Is it a linear, or switch-mode? How many output rails are there? does the
instability affect them all, or only one or two?

The caps were
replaced

All of them?

and the problem was rectified. Well, within a couple of
months the fault is back,

So probably not capacitors then, unless it's the ones that got missed last
time. (Is the fault *exactly* the same?) Maybe the instability is the
result of a broken PCB track, dry joint or poor connection somewhere that
makes contact when it wants too, and the "cure" last time was due to the
physical handling of the PSU causing this to make contact again, for a
while.

and instead of paying silly prices to one of
the very few tape machine repair guys around, my mate wanted me to fix
it if I could find the faulty caps. The last repair cost £500. The
tape machine is a Saturn Soundcraft, and aparently there is only one
person in the country who can repair them (he lives in Bury St.
Edmunds).

Unlikely. Unless the machine was designed on Saturn (or in Bury St Ed) any
competent repair technician ought to be able repair it.

David.


What's wrong with Bury St Edmunds? My designs generally work.......
S.
--
http://audiopages.googlepages.com

On Fri, 3 Oct 2008 21:28:09 +0100, "David Looser"
wrote:

"Marky P" wrote in message
.. .

Basically, there was a severe buzzing noise on the output and the
fault was traced to the PSU supply not being stable.

Is it a linear, or switch-mode? How many output rails are there? does the
instability affect them all, or only one or two?

Unfortunately I haven't looked at it myself, so I don't know.

The caps were
replaced

All of them?

Again, I'm not sure. Wouldn't've thought so.

and the problem was rectified. Well, within a couple of
months the fault is back,

So probably not capacitors then, unless it's the ones that got missed last
time. (Is the fault *exactly* the same?) Maybe the instability is the result
of a broken PCB track, dry joint or poor connection somewhere that makes
contact when it wants too, and the "cure" last time was due to the physical
handling of the PSU causing this to make contact again, for a while.

and instead of paying silly prices to one of
the very few tape machine repair guys around, my mate wanted me to fix
it if I could find the faulty caps. The last repair cost £500. The
tape machine is a Saturn Soundcraft, and aparently there is only one
person in the country who can repair them (he lives in Bury St.
Edmunds).

Unlikely. Unless the machine was designed on Saturn (or in Bury St Ed) any
competent repair technician ought to be able repair it.

David.


Marky P.

"Marky P" wrote in
message
Hi,

Is it possible to test capacitors reliably without a
capacitance meter?

Yes, if you have some fairly precise reference parts, you can set up a
capacitance bridge on the bench that allows you to measure capacitance and
series R by indirect means.

http://www.allaboutcircuits.com/vol_2/chpt_12/5.html

Phil Allison wrote:

True, but with modern equipment the vast majority of faulty capacitors...
** So ****ing what ?
The OP never alluded to what sort of caps he wanted to test.
So your assumption is 100% FALSE !!!!!!!!

You know, when I see an outburst like this I always imagine the poster
sat at the computer wearing his underwear and a straight jacket, typing
by picking up a pencil in his teeth and dribbling everywhere.

Either that or wearing a dress like the character "Anne" in the popular
British comedy "Little Britain".

--
Squirrel Solutions Ltd Tel: (01453) 845735
http://www.squirrelsolutions.co.uk/ Fax: (01453) 843773

Registered in England: 05877408

Glenn Richards wrote:
Phil Allison wrote:

True, but with modern equipment the vast majority of faulty
capacitors...

** So ****ing what ?
The OP never alluded to what sort of caps he wanted to test.
So your assumption is 100% FALSE !!!!!!!!


You know, when I see an outburst like this I always imagine the poster
sat at the computer wearing his underwear and a straight jacket, typing
by picking up a pencil in his teeth and dribbling everywhere.

Either that or wearing a dress like the character "Anne" in the popular
British comedy "Little Britain".



http://xkcd.com/386/

--
Nick

"Glenn Richards" wrote in message
...
Phil Allison wrote:

True, but with modern equipment the vast majority of faulty
capacitors...
** So ****ing what ?
The OP never alluded to what sort of caps he wanted to test.
So your assumption is 100% FALSE !!!!!!!!

You know, when I see an outburst like this I always imagine the poster sat
at the computer wearing his underwear and a straight jacket, typing by
picking up a pencil in his teeth and dribbling everywhere.

Either that or wearing a dress like the character "Anne" in the popular
British comedy "Little Britain".


And, as it turned out, my assumption was 100% correct!

David.