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.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #21   Report Post  
Old May 23rd 21, 02:07 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2007
Posts: 2,017
Default Faulty SMPSU.

On Saturday, May 22, 2021 at 2:31:00 AM UTC-7, T i m wrote:
On Mon, 17 May 2021 15:43:12 -0700 (PDT), whit3rd
wrote:


... the low-voltage rectifier (if it really IS rated for 20A, it has to
be heatsinked); if it's leaky it would be a quasi-short-circuit, and that will deliver
AC to the capacitors you replaced, which would kill 'em soonish.


Coming back to this before buying / replacing the switcher, I tested
it out of circuit on my DMM (diode test, all ways etc) and it seemed
to check out ok?


They almost always fail with a dead short, couldn't miss that with
a diode check ( 0.2 to 0.8V is a typical good-rectifier reading forward,
and no conduction in reverse).

FWIW I measure about 10V DC on the output (no load) and only about .5V
on the AC range


Since the capacitors on output were replaced, are you sure they're low-ESR types?
The ripple current ratings have to add up to about the output (20A) of the unit.
Correct capacitance but low ripple current ratings (aka high ESR) on the replacements
could explain bad output with good rectifier.

  #22   Report Post  
Old May 23rd 21, 07:20 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jul 2006
Posts: 13,431
Default Faulty SMPSU.

On Sat, 22 May 2021 18:07:17 -0700 (PDT), whit3rd
wrote:

On Saturday, May 22, 2021 at 2:31:00 AM UTC-7, T i m wrote:
On Mon, 17 May 2021 15:43:12 -0700 (PDT), whit3rd
wrote:


... the low-voltage rectifier (if it really IS rated for 20A, it has to
be heatsinked); if it's leaky it would be a quasi-short-circuit, and that will deliver
AC to the capacitors you replaced, which would kill 'em soonish.


Coming back to this before buying / replacing the switcher, I tested
it out of circuit on my DMM (diode test, all ways etc) and it seemed
to check out ok?


They almost always fail with a dead short, couldn't miss that with
a diode check ( 0.2 to 0.8V is a typical good-rectifier reading forward,
and no conduction in reverse).


Agreed. I think I read .2xxV on my DMM diode test in the forward (x2)
and as you say nothing in the reverse (x2 + 2 (between the two
outers)).

FWIW I measure about 10V DC on the output (no load) and only about .5V
on the AC range


Since the capacitors on output were replaced, are you sure they're low-ESR types?


I believe they we

"Panasonic 1000uf 16v Electrolytic Capacitor 105 LOW ESR FR Series
EEUFR1C102L" ?

https://industrial.panasonic.com/ww/...ls/EEUFR1C102L

The ripple current ratings have to add up to about the output (20A) of the unit.
Correct capacitance but low ripple current ratings (aka high ESR) on the replacements
could explain bad output with good rectifier.


(Interesting, thanks) From that spec the only value I can see related
to ripple is:

"Rated ripple current-1 (mA) 1560.0"

So the 4 would give 6.24A but would that still impact the off load
voltage?

I might see if I can rig up my USB scope and actually 'see' what the
output is doing.

Cheers, T i m

p.s. Because I need the 3D printer running I've since bought 2 x Mean
Well (SP-200-12) 12V x 16.5A PSUs and have tacked them in to be able
to get going (and need to design and print some new mounting brackets
g). However, whilst it looks like I could end up spending ~10 GBP
(more if you count to total cost when it's more sensible to buy 10 off
something when I only need one) to get this old PSU running (assuming
I ever do etc) and could buy another cheap one new for just a few
pounds more, I am interested to see if I can get it going (with the
guidance of some good folk here etc g), firstly, because I would
find it satisfying, second because I then have a spare PSU and third I
wouldn't them have to throw the rest away. ;-)


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
SMPSU T i m UK diy 24 May 18th 21 11:54 AM
Faulty Thermostat or faulty installation Chris B[_2_] UK diy 16 April 19th 21 05:51 PM
Panasonic TU-DSB3 SMPSU primary. Ian Field Electronic Schematics 0 July 9th 12 05:47 PM
SMPSU ZH 015A Pretorlf Electronics Repair 0 September 9th 05 09:36 PM
anyone know how to diagnose a faulty Choke / Ballast in fluorescent light circuit nick UK diy 14 July 7th 03 02:01 PM


All times are GMT +1. The time now is 04:47 PM.

Powered by vBulletin® Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Copyright 2004-2022 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017