Wier WA505 SMPSU output failed

[CapLeaker]

Re: Wier WA505 SMPSU output failed

As long as these main input filter caps are within 20% of the rating, I don’t see it as a reason of what this PSU is doing right now.

[stj]

Re: Wier WA505 SMPSU output failed

ZLK is nice

[nath1977]

Re: Wier WA505 SMPSU output failed

I think ive worked it out but not yet been able to try. There are remote sense outputs which I didn't connect when testing. Id imagine thats the problem!...

This document prompted the thought. https://cdn.badcaps-static.com/pdfs/...06ef55eb63.pdf

It seems like a plausible reason for the low voltage on the 5v, and based on some other reading, the auxiliary voltage outputs on PSU's tend to rely on the primary working properly and under some load.

Every day is a school day.

Will report back....

[CapLeaker]

Re: Wier WA505 SMPSU output failed

There are supposed to be shorting bars or jumpers installed. Even sez so. We had no idea that there are sens pins on the terminals.

[stj]

Re: Wier WA505 SMPSU output failed

i hate sense inputs.
if you get a poor connection the output ramps up until it hits a limit or you burn something!

[CapLeaker]

Re: Wier WA505 SMPSU output failed

i hate sense inputs.
if you get a poor connection the output ramps up until it hits a limit or you burn something!

That's probably why it went first place.

[nath1977]

Re: Wier WA505 SMPSU output failed

Hmmm joining the sense pins to the main output has made no difference to the voltage. ��

[CapLeaker]

Re: Wier WA505 SMPSU output failed

On this PSU the you have to jump sense + to positive and sense - to negative. There should have been shortening bars that came with it. I guess either there is something wrong with the regulation / sense circuit if the shortening bars do nothing.

[stj]

Re: Wier WA505 SMPSU output failed

maybe look for burned resistors.

a good example of why sense lines are a bitch is to search "atari ar2"

[nath1977]

Re: Wier WA505 SMPSU output failed

My search continues…

I've sketched out the main components of the main output low voltage side and struggling to get a voltage reading across the transformer output prior to the rectifiers. Post rectifier diodes I get 3.5v, prior I get nothing. Will tidy my sketch and upload here. Any ideas?

[CapLeaker]

Re: Wier WA505 SMPSU output failed

Probably because your meter was still set in DC. You can’t send straight DC through a transformer. The rectifier diode is there for a reason on the output. Put your meter into AC mode and measure again.

[nath1977]

Re: Wier WA505 SMPSU output failed

Thanks - I am aware I need AC setting though may have had a brain fade at the time. Will try later and use another meter too.

Here is a partly completed diagram https://www.digikey.co.uk/schemeit/p...5ca94532b4a1f0

The heavy duty busbars soldered on the component side are labelled and Ive added them to the diagram.

BB2 to BB7, 3.5vdc
BB2 to BB1, 0vac
BB2 to BB5 - need to check!

R205 looks like it might be the sense feedback.

Are T200 and T201 for measuring current as one side is a simple loop, and the other side has a lot of small windings.

T4 is the big planar? transformer with other outputs too.

There is a TH thermistor? fastened to the heatsink.

Will add more detail as I go.

[nath1977]

Re: Wier WA505 SMPSU output failed

Probably because your meter was still set in DC. You can’t send straight DC through a transformer. The rectifier diode is there for a reason on the output. Put your meter into AC mode and measure again.

Re-tested and ensured I was on AC and tried a second DMM too. Nothing between BB1 and BB2. Resistance is 0.3 Ohms though it looks like some big fat metal plates, which if they had failed would have been pretty obvious.

BB2 to BB7 and BB2 to BB5 both read 3.5vdc.

[CapLeaker]

Re: Wier WA505 SMPSU output failed

Here is a partly completed diagram https://www.digikey.co.uk/schemeit/p...5ca94532b4a1f0

this link doesn't work for me.

[stj]

Re: Wier WA505 SMPSU output failed

f that link - not putting up with at!

Scheme-it
The app is loading, please wait.

Initializing application...

[nath1977]

Re: Wier WA505 SMPSU output failed

this link doesn't work for me.

PDF copy...

[CapLeaker]

Re: Wier WA505 SMPSU output failed

BB2 to BB1 you may not be able to measure that AC with an DMM since it isn’t going 60Hz rather it’s going like 60KHz. Maybe try an oscilloscope?
These type of power supplies are very complicated and probably my least favourite. Maybe there is something wrong with the feedback and something is higher in resistance than it should be?