Identifying leaking caps

[SleepLess]

Hi.
A friend of mine has dropped his silverface Princeton at home for an inspection. It's from 1978. Apparently one of the power tubes got blue, the amp purred and then stopped working. I have changed the 1A fuse which had blown and I'm about to insert newer tubes to check if everything's ok. Everything's ok without the power tubes except that the amp has a 5U4 instead of the GZ34.

But for this repair and other repairs I'd like to know how to spot leaking caps, be them filter or coupling caps. Is there a common method? Say for instance if a guy tells me "I'm dropping you my amp, please check that all the caps are still good and replace only the bad ones". How do I check that?

Thanks a lot!

[stratele52]

Coupling cap ; in the amp ,
1- Read DC voltage boths side of the cap .Amp ON
2- Disconnect side with lower voltage , this is the "output" . Amp OFF
3- Read DC voltage at this end , more than 1/5 volts ( 0.20 V ) , caps is leaking . Amp ON


Filter caps ;
1-  Quality Capacitor checker with high voltage supply

Or
1- Read AC voltage ; more MFD less AC ripple

Or the best put a new cap in parallel on the old one ; look how amp work, AC voltage reading ( ripple )

[SleepLess]

Coupling cap ; in the amp ,
1- Read DC voltage boths side of the cap .Amp ON
2- Disconnect side with lower voltage , this is the "output" . Amp OFF
3- Read DC voltage at this end , more than 1/5 volts ( 0.20 V ) , caps is leaking . Amp ON

Thanks for this, pretty clear explanation!

Filter caps ;
1-  Quality Capacitor checker with high voltage supply

What reference have you got in mind? I'd liek to check a good affordable one out!

Or
1- Read AC voltage ; more MFD less AC ripple

Can you explain this more?
Thanks!!!

[stratele52]

Quality capacitor checker ; I don't know nothing affordable to do the job , tool for tech $$$.
 I have Heatkit Capacitor Checker Model IT-28 . It is a vintage tester

AC Ripple on cap. I don't know how too explain shortly, and no time for now . Sorry , Google ?

[SleepLess]

Have you guys ever tried or bought the Peak Atlas ESR70? Is it any good?
Thanks!

[stratele52]

Have you guys ever tried or bought the Peak Atlas ESR70? Is it any good?
Thanks!

As I read this tester is only good to read capacitance and ESR. Can't test capacitor leakeage and dischage like my Heatkit.

Most of the time old cap have a "good " capacitance but don't work properley .

[SleepLess]

I have just sent Peak an email to ask if their Atlas ESR70 can test capacitor leakage. As for discharging capacitors, it does (automatically).

Your Heathkit IT-28 looks pretty good and affordable but I need a 230V power ability (I'm in the EU) and I've only seen 110V units... And I would also like a smaller package if possible... If you know anything that would fit, don't hesitate!

Thanks!

[stratele52]

I have just sent Peak an email to ask if their Atlas ESR70 can test capacitor leakage. As for discharging capacitors, it does (automatically).

Your Heathkit IT-28 looks pretty good and affordable but I need a 230V power ability (I'm in the EU) and I've only seen 110V units... And I would also like a smaller package if possible... If you know anything that would fit, don't hesitate!

Thanks!

Peak can't do that , no high voltage power supply, just a battery .

For use Heatkit with 230 volts  , you just need transformer 230 to 120 AC

[stratele52]

I have just sent Peak an email to ask if their Atlas ESR70 can test capacitor leakage. As for discharging capacitors, it does (automatically).

Look here , at the end of the page there is a user manual say all ;

www.peakelec.co.uk/acatalog/jz_esr60.html