Testing capacitors
 

Don Pearce wrote:

You don't have a multimeter with a needle? You are missing one of the
best alignment tools anyone could own - and a handy capacitor tester of
course. Go out and buy one now - it isn't a replacement for a DMM, but a
very useful complement.

Handy for measuring noise too due to the mechanical time constant. Noise tends
to send DVMs nuts.

Graham

Testing capacitors
 

Phil Allison wrote:

"Patrick Turner"


Indeed, and I forgot these valid points in my last post.


I think the OP mainly wanted the C value.

** Then it would indeed profit the good fellow - most greatly -

to learn how to ****ING READ !!!!!!!!!!!!

....... Phil

"The good fellow" ??

I didn't think there was one left...

Patrick Turner

Testing capacitors
 

On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:

"Patrick Turner" wrote in message
...



ESR is measured in other ways, but it seems the OP wanted to know how to
work out the C value without a C meter.

Does it? the OP talked about "testing" a capacitor, not "measuring" it; that
sounds to me more like someone who wanted to know whether a capacitor was
faulty.

Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder

Marky P.

Testing capacitors
 

On Tue, 30 Sep 2008 22:11:57 +0100, "Ian"
wrote:


"Marky P" wrote in message
.. .
Hi,

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


Marky P.

Yes, put your tongue across the contacts a few seconds after switching off.

A bit more awkward when the caps are still on the board :-)


Marky P.

Testing capacitors
 

"Marky P" wrote in message
...
On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:


Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder


Faulty capacitors in power supplies usually make themselves apparent by such
problems as low voltage or excessive ripple on one or more of the output
lines, or rather more obviously by leaking electrolyte, bulging seals etc.
In view of the age of this unit your best bet is probably simply to replace
any suspect capacitors rather than bothering to try and test them.

David.

Testing capacitors
 

In article ,
Marky P wrote:
Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder

Which one?

If an analogue PS a faulty cap would usually just cause hum, etc. If
switch mode you'll really need an ESR metre to check them.

--
*It ain't the size, it's... er... no, it IS ..the size.

Dave Plowman London SW
To e-mail, change noise into sound.

Testing capacitors
 

On Fri, 3 Oct 2008 16:47:49 +0100, "David Looser"
wrote:

"Marky P" wrote in message
.. .
On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:


Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder


Faulty capacitors in power supplies usually make themselves apparent by such
problems as low voltage or excessive ripple on one or more of the output
lines, or rather more obviously by leaking electrolyte, bulging seals etc.
In view of the age of this unit your best bet is probably simply to replace
any suspect capacitors rather than bothering to try and test them.

David.

Basically, there was a severe buzzing noise on the output and the
fault was traced to the PSU supply not being stable. The caps were
replaced and the problem was rectified. Well, within a couple of
months the fault is back, 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).

Marky P.

Testing capacitors
 

On Fri, 03 Oct 2008 17:08:43 +0100, "Dave Plowman (News)"
wrote:

In article ,
Marky P wrote:
Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder

Which one?

If an analogue PS a faulty cap would usually just cause hum, etc. If
switch mode you'll really need an ESR metre to check them.

As mentioned in the above post, it's a Saturn Soundcraft 24 track.

Marky P.

Testing capacitors
 

"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.

Testing capacitors
 

Marky P wrote:

On Wed, 1 Oct 2008 10:42:53 +0100, "David Looser"
wrote:

"Patrick Turner" wrote in message
...



ESR is measured in other ways, but it seems the OP wanted to know how to
work out the C value without a C meter.

Does it? the OP talked about "testing" a capacitor, not "measuring" it; that
sounds to me more like someone who wanted to know whether a capacitor was
faulty.

Since the OP has remained silent since his first post what he actually
wanted remains a mystery.

David.

Very sorry! I forgot made this post (someone over at alt.digital.tv
remined me). I want to test for faulty caps. It's in a power supply
unit in a 1980's professional multi-track tape recorder

Marky P.

Try just replacing it with another of the right type. If the problem of
noise or silence vanishes, maybe its the cap. Hire a tech to find out
for you? every tech knows what to do about testing a cap for a
fault/leakage and its been discussed many times here and else where.

Reading the circuit should inform you of the Vdc across the cap and hum
voltage, so if there is a lot of hum and Vdc is low, and there are hot
parts, then maybe the circuit powered by the Vdc is drawing too much
Idc. Take the wholeistic approach, or else put up with wrong
diagnosies.

Patrick Turner.