Source for replacement caps in H744 regulators

[Rob Jarratt]

> -----Original Message-----
> From: Jonathan Chapman <lists at glitchwrks.com>
> Sent: 06 January 2022 13:00
> To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
> Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
> Subject: RE: Source for replacement caps in H744 regulators
> 
> > One of the H744 regulators whines
> 
> FWIW, none of mine are silent under load. If they're not being loaded (e.g.
> on a test bench, with no dummy load, or if you have all the boards out) they
> can whine excessively due to no minimum load.

I was testing with a 1R resistor, so drawing 5A of the rated 25A. The other two H744s did not whine, but this one does. I can try a bigger load, I think the best I may be able to do is 10A, possibly 20A.

> 
> > it seems higher than the expected values printed on the meter
> 
> Beware cheap test equipment. $client has a few of these Chinese handheld
> LC/RLC meters, they're wildly inaccurate on some parameters, including ESR
> on large electrolytics. We've got a proper Gen-Rad RLC Digibridge in the shop
> to compare against. We couldn't figure out why some of their tuned filter
> stages were failing QC at a much higher rate than expected. They were off-
> frequency because the cheap meters were giving consistently incorrect
> measurements when trying to match capacitors.
> 

My ESR meter is built from a design by Bob Parker. I got it from someone in Portugal (https://evbesrmeter.pt/), so I don't think it is a cheap Chinese one.

> That said, it's not like replacing them with new will *hurt* -- it just might not
> fix the whine.
> 
> Thanks,
> Jonathan