Apple G4 AcBel API1PC36 PSU has a bad cap?

[Xandros]

Hello! I've seen quite a few posts on here regarding these PSU's. And indeed, there's quite a few places around the net of people having general issues with these supplies in their PowerMac G4's. Mine seems to exhibit a slightly different problem though.

The usual problem is, the Mac won't turn on, lights might flicker etc. I've also seen some people experience their Mac refusing to turn on unless they had an ADC monitor connected. My problem is the opposite to the latter, it won't turn on with an ADC monitor connected, but it turns on just fine without it plugged in. I do have another identical ADC monitor that the Mac will turn on when it's plugged in but it will randomly turn off and lose power, sometimes a few seconds after the Mac is turned on, sometimes it can last an hour (the Mac stays on just the monitor dies).

Everyone I've talked to about this has either been stumped or merely told me that my PSU is the likely culprit based on the fact I have a MDD and their PSU's are prone to failures. Some have suggested the monitor's probably have faulty inverter boards.

I figured I might as well open the PSU up and look inside it though given, they are prone to failures. And I have found one cap that appears to be bulged:

Here's a wider shot of the area with the cap hidden under the two black wires you can see, and then a close up with the apparent bad cap circled in red:


I notice in the other topics regarding these PSU's that, it's generally recommended to replace at least the main cap anyway, and probably a whole spread of caps too to be on the safe side.

The thing I'm wondering here is, is it indeed possible that one bad cap like the one I've pointed out (if it is bad that is) could cause the machine to refuse to turn on when there's an ADC monitor connected (but otherwise work fine when it isn't plugged in)? Or of course, power the monitor for a bit but eventually get fed up and die after a while as it does with the other monitor?

Or is it more likely these oddities with the monitors is a result of faulty monitor inverter boards or something and the PSU is actually OK (well, apart from that one cap)? Anyway, much appreciate any help I can get on this, I am a novice with basic soldering experience and, maybe some ability with a cheap multimeter, so nothing spectacular as you may have guessed.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

I've just realised I posted this in the wrong forum somehow. I think because I was browsing a thread about this model of PSU that was actually in this forum as opposed to the PSU forum. I can't edit it apparently so perhaps when a mod sees this they could move it to the Power supple design and troubleshooting forum instead. Thanks.

[dragos2009]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

yes that cap is definely bad and i would suggest you to change it

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Thanks for the advice. I've finally got round to pulling it. It's a Teapo, 1000uF, 10v, "SC105°" and says 10/03 and A3 under that. I'm guessing 10/03 is the date of manufacture?

Seen a lot of people suggest these Teapo caps can be a bit crap. Would anyone recommend a particular brand in it's place? I'm assuming I should go for a like for like replacement.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

So far, the only cap I've come across that seems similar is a Panasonic FC series.

It's the same size, uF and voltage and 105 degrees. I was looking at the Teapo cap specification sheet and trying to match them, and they're pretty much the same across the board except the Panasonic cap's max ripple is 995, where as the Teapo's is 1080. The max impedance is the same though at 0.065.

Is a difference of 85 in the ripple going to make a blind bit of difference? There are more caps I can look at but, I'm guessing that unless I find one bang on the same values (presumably unlikely) then a slightly lower max ripple is probably better than a slightly higher one or is that entirely wrong? Needless to say I haven't got a clue.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

how does the teapo compare to panasonic FR series? probably the FR is better.

btw, higher ripple is better - because it's ripple handling.

[ReeceyBurger123]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

how does the teapo compare to panasonic fr series? Probably the fr is better.

Btw, higher ripple is better - because it's ripple handling.

+1

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

So a cap with a higher max ripple and lower impedance would be better at the job than the old cap? Only there's a Rubycon ZL series here that's around 1250 max ripple and 0.041 impedance, same values everywhere else though (1000uF, 10v, 8x20mm, 105 degress) as the Teapo by the looks of it.

[ChaosLegionnaire]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

caps generally have a ±20% tolerance. so u can use any cap that is within 20% of the original's rated specs (capacitance, esr, ripple) without any nasty side effects or anything bad happening but NOT voltage!!! u want the same voltage or higher not less! unless u know what u are doing... e.g. some mobos use 10v caps for the 5v rail, in this case using a 6.3v cap is fine... since u are doing this for the first time, i suggest sticking to 10v caps.

btw, i'm not too familiar with how the psu in a mac is set up. is that psu just for powering the monitor or is the same psu used to power the motherboard where the cpu, ram and hard drive are as well? if its the former case, the panny fc will be fine as 80ma of ripple filtering isnt really critical for a monitor circuit. if its the latter, the mobo will prefer the lower esr of the ruby zl cap. the hard drive will also love the higher ripple handling and last longer!

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Hi. Yes I thought it might be wise to stick with the same voltages as the original cap, I've no idea what line volatge it's on but either way thanks for confirming that for me. Also the PSU powers the monitor and the rest of the computer. There's a 25v line that goes to the connector on the mobo that gets routed to the graphics card's ADC port for use with specific monitors.

It's because of the ADC monitors that I'm having issues of course. I don't know if this solitary bulged cap I shall replace is going to solve all the issues as I may even have a couple of faulty monitors to boot but I guess I won't know until I try.

I shall get the rubycon cap then and see what trouble I get myself into with it (lol). I've got a vague suspicion I'll probably end up having to replace more than one cap in this PSU since in all other posts I've read about it on here and other places that's what people seemed to be recommended to do, I'll be back with results anyway.

Cheers!

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

I got around to soldering the new cap in, put the PSU back together enough for it to work and hooked it back up. Unfortunately the newer monitor I have that doesn't allow the Mac to turn on unless I unplug/plug the monitor back in is still exhibiting those issues.

The older monitor that always did work but randomly used to turn off and remain off has thus far remained powered on while it's been in use. I'm not holding my breath on that though as like I say it exhibited the issue randomly; sometimes it'd work for hours other time it'd work for all of thirty seconds. Fingers crossed anyway that bad cap had something to do with it though I'm being pessimistic merely because most people that have repaired these PSU's have replaced quite a few caps across the board, not just one like I have, so I'd be silly to expect perfect results based on that knowledge.

Edit: On second thoughts having had it running for a while... I think the PSU is actually worse than it was before I started messing around with it. I've only just realised but it's making a prolonged creaking or clicking sound now. I think it did this before but I always assumed it was the hard disc but, it's not the hard disc as I've now realised since I leaned over to pick something up and realised the noise was coming from the PSU... Odd. Can't say I noticed it before either, though I'm not sure as it might have done it before but not as audible? If I move the mouse cursor around the screen the noise changes pitch too (hence why I thought it was the Hard disc at first).

At any rate, the oddities don't stop there. The system seems to hang now. OS X works, I can move the mouse around but that's about it. Works fine for a few minutes initially then I can't really do anything else except move the mouse around. Mac also doesn't seem to go to sleep properly anymore (it goes to sleep, eventually, if I press the button but all the fans stay on in the computer, though the PSU does stop making that weird noise). Before when you put it to sleep the fans would all turn off too and the power lights would start to glow.

Soooo... Yea. I guess I was right in thinking it needed more work doing to it than just replacing one bad cap. But, didn't think at all that replacing one obviously bad cap would actually make it worse... Or that it would have quite such an impact on the system as a whole.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

maybe it's the monitors too.

monitor caps seem to fail a lot faster than pc psu ones.
maybe because the psu has a fan.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Yea, quite possibly. I had thought perhaps the issue was monitor related but whenever I brought it up on the various Mac forums I frequented trying to gain answers to the problems, as soon as I let slip it was a Mirror Drive Door PowerMac everyone always seemed to just automatically brush it off as my PSU was the culprit since "they're prone to it" and I'd get no further responses.

With regards to the PSU making that weird noise though as per my edit above, I have since tried unplugging the monitor while it was running and the noise didn't go away. So clearly I've done something bad to it.

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

given the age of the psu, i would replace any cap that is 220uf or less.

i dont know that model, but i have an AC-BEL from a blue G3 and they are very well built.
most are made by Lite-ON.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

I shall do that then at some point. I might replace some/all of the other capacitors that are dotted around the area where the old bad cap was too while I'm at it. I'll forget about the monitors for now and work on having the PSU functioning like it was before I messed around with it at least.

Should I follow the same general rule of thumb as I did above when replacing the other cap, ie replacing a cap with one of the same voltage/uF/etc but that has a slightly higher max ripple and lower impedance is OK to do?

[stj]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

higher ripple is good, slightly lower impedence is fine.
watch the diameters because it's going to effect the distance between the wires too.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

Yea, I'll try and source caps of the same size where possible. I did with the other cap so it fit back in place of the old cap perfectly given how bloody awkward it was getting it out in the first place. Thanks!

Might be a while before I get around to doing this overhaul because of life getting in the way but I'll be back with results eventually.

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

A minor update: It looks like the problems were just the monitors being faulty and not the PSU after all (though I expect my PSU did and still does need an overhaul given it did have that one bad cap). Anyway long story short I was lucky enough to find another PSU identical to mine selling really cheap and in good working condition so I just slapped that in the Mac and tried the two monitors and they both exhibit the same problems.

No idea what's wrong with the one that refuses to let the Mac turn on but the one that would work but randomly turn off appears to be a backlight problem. I'd never noticed before (either because it didn't do it with the old PSU in place or because I just wasn't patient enough to look at it long enough to notice) but the power light flashes short-short-long now after it "turns off", which apparently means a backlight issue.

Sure enough shining a flashlight on the screen I can just about make out the desktop so, guess next stop is to open that up and have a look at the inverter board on it (will make a new topic about that though if I need help given it's not really related to this one, or PSU's in general seeing as these monitors don't have an internal PSU).

[Stefan Payne]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

btw, i'm not too familiar with how the psu in a mac is set up. is that psu just for powering the monitor or is the same psu used to power the motherboard where the cpu, ram and hard drive are as well?

Both...
There is a +25V Rail that's for the monitor, if you use an ADC one.

The rest is for the innards of the MAC.

I also have a G4 PowerMAC with an ACBEL Power Supply here...
And a GF4 MX with an ADC connector...

[Xandros]

Re: Apple G4 AcBel API1PC36 PSU has a bad cap?

So I thought I'd come back to the old PSU and carry on rebuilding it. But I have a question to put to you experts!

Before I took the PSU apart, it worked OK (the problem I had of course was the monitor not the PSU, even thought the PSU had a buldged cap it seemed to be functional in all other respects as far as I could tell). In the end I actually got another identical PSU as a bonus for buying some parts for the Mac so I left the old PSU as something to at a later date.

Anyway to recap (pun not intended) all I did was replace one cap (Teapo) with another (Rubycon) of the same size, voltage and uF rating, (1000uF and 10v) just with a slightly higher ripple (1250 over the original 1080) and a lower impedance (0.041 over the original 0.065).

It looked OK, put it all back together, powered it up but it was "squealing" quite badly. I'm fairly sure it didn't do this before I replaced the cap so, I just wonder what might cause that squealing noise to occur and, if it's because I made some sort of cock up with the replacement? Thanks.