Is it worth trying to fix a power supply?

[Fama]

I was using my huge pedalboard a little ago and suddenly it started malfunctioning. Just a slow motorboating type sound, some pedals not lighting up, smelled like burning. I finally got around to troubleshooting in more detail, and it looks like my Truetone 1Spot CS12 is broken.

To be more accurate, the changeable 9V/12V outputs are outputting less than 1V each in either mode. Same with the 18V outputs on that same side. The other outputs seem to work fine, although I only tested them one by one with a multimeter and not under load.

What do you think, is it worth opening it up and trying to fix it? Obviously it has 230V running into it, and I wouldn't plug it in while the case is open, but I'm feeling a bit iffy about doing DIY repairs on it.

I bought it used over a year ago, and the date code seems to say it's from 2015 originally, so no chances of warranty.

Edit: I popped it open, each output has it's own voltage regulator (or at least I assume that's what they are, huge heat sinks). I doubt 6 of those just broke at the same time, but I can't see where there could be a split between either side (first 6 do not work, the other 6 presumably work, I didn't test the AC but the other 5 work), or if they are somehow partially chained and the issue could be where the chain is. A ton of caps and diodes, no visible signs of problems.

 

[Feral Feline]

Glad you're keeping the old supply Fama, because as your abilities and confidence grow, you may come back to it and get it working. ( I sure hope so!)

I'm with Chris Knudson on checking to make sure the big caps are fully drained even if it's been a few minutes.
Since you're like me and new to the high-voltage stuff, and even if we were old hands (hacks?) at it...

It's just simply good procedure/practice/habit to ALWAYS make sure everything's drained — it doesn't take long to do so, and if ever something goes awry with whatever equipment you're working on and after a few minutes it doesn't drain itself for whatever reason...

 

[Fama]

Glad you're keeping the old supply Fama, because as your abilities and confidence grow, you may come back to it and get it working. ( I sure hope so!)

I'm with Chris Knudson on checking to make sure the big caps are fully drained even if it's been a few minutes.
Since you're like me and new to the high-voltage stuff, and even if we were old hands (hacks?) at it...

It's just simply good procedure/practice/habit to ALWAYS make sure everything's drained — it doesn't take long to do so, and if ever something goes awry with whatever equipment you're working on and after a few minutes it doesn't drain itself for whatever reason...

That's a good point, at this stage it has been unplugged for weeks I think, so I'm fairly sure it's all drained, but like you said - it's a good habit to develop (and practice with something where I probably won't get a shock even if I mess it up a little).

I probably wouldn't have tried this if I didn't get a really good tip about where the issue is because there's just so many components, and I figured it wouldn't be something as simple as a diode on one of the channels, so that's definitely at least worth a shot.

 

[mzy12]

I am gonna reverse engineer this power supply at some stage, because it is very good, but has some less than perfect design choices. (Power LED runs on the 9VAC transformer and the fact that the 9VAC is derived from a transformer on the mains means you still have to choose the input AC voltage). Obviously, Feral is correct in mentioning you need to discharge the caps, normally I do mention it any time I discuss SMPS stuff, I just forgot this time haha. Only time I've ever got zapped was from one of those bad boys!

 

[Spiff4565]

My Voodoo Labs Pedal Power 2 started humming.

Popped the cover off and found one of the 1000uF caps bulging. Took it out and the dielectric was leaking out the bottom.

So I replaced all the electrolytic caps. Him was greatly reduced but not zero.

Replaced all electrical with low ESR caps. Unfortunately I didn't order the correct quantity of the 10uF's, but those will arrive today.

I also replaced all eight of the power regulators, just because I was already in desoldering mode. Those are now replaced.

The only thing I have not replaced are these things, as I have no idea what the are:




I don't believe there is anything exotic or overtly technical in a typical PS. I'd say crack the beast open and see what's under the hood.

 

[Fama]

My Voodoo Labs Pedal Power 2 started humming.

Popped the cover off and found one of the 1000uF caps bulging. Took it out and the dielectric was leaking out the bottom.

So I replaced all the electrolytic caps. Him was greatly reduced but not zero.

Replaced all electrical with low ESR caps. Unfortunately I didn't order the correct quantity of the 10uF's, but those will arrive today.

I also replaced all eight of the power regulators, just because I was already in desoldering mode. Those are now replaced.

The only thing I have not replaced are these things, as I have no idea what the are:
View attachment 76212

View attachment 76213

I don't believe there is anything exotic or overtly technical in a typical PS. I'd say crack the beast open and see what's under the hood.

Best I could find for AM151 is that it might be a bridge rectifier diode, and here could be an alternative https://www.newark.com/multicomp-pr...h/dp/99AC4581?rpsku=rel3:AM151&isexcsku=false which does look sort of similar. But I could also be very wrong, and I can't make anything of the presumed manufacturer name above the AM151. Do the components have 4 legs (you should be able to check on the underside)?

 

[Spiff4565]

Best I could find for AM151 is that it might be a bridge rectifier diode, and here could be an alternative https://www.newark.com/multicomp-pr...h/dp/99AC4581?rpsku=rel3:AM151&isexcsku=false which does look sort of similar. But I could also be very wrong, and I can't make anything of the presumed manufacturer name above the AM151. Do the components have 4 legs (you should be able to check on the underside)?

Yes, it has four legs. Thank you for researching this. so far after replacing all the caps and power regulators it appears to be cured of its hum.

 

[andrewsrea]

Yes, it has four legs. Thank you for researching this. so far after replacing all the caps and power regulators it appears to be cured of its hum.

The mystery component is a 'bridge rectifier,' consisting of an interval array of four 1N4003 or 1N4004 equivalent diodes. They either work (change AC to DC with a small ripple, hence the filter caps and chokes), or don't they work (typically short out, then fry then measure 'open'), It is unlikely with what you have said so far, that it needs to be replaced.