Safely opening Amiga Brick Power supplies?

[AmiNeo]

Let me repeat...


Guys, is it possible to test this without opening it atall with a multimeter? I'd imagine so but I'm not sure how you'd go about it...

---------- Post added at 12:21 ---------- Previous post was at 12:18 ----------

disclaimer!

if anyone here believed my remark about licking PSU caps, then i'm sorry but you deserve to die! it's natural selection or just plain old Darwinian!

I didn't Juv, hence my response


But since its not only members that read this... lol. Better safe than sorry. I can just imagine some idiot doing a google search on how to test capacitors and spotting your comment... "Ohhhh, LICK IT!" ... BZZFTTT!!! :nuts:

 

[Elerion]

Guys, is it possible to test this without opening it atall with a multimeter? I'd imagine so but I'm not sure how you'd go about it...

Yes
You could measure the AC component within DC output while in full operation. Higher values sugest that caps may be dry.
The thing is... You don't know what nominal values are, so...

There are other methods.
- You can easily check for leaking caps by visual examinantion.
- You can check if audio is clear wiht no brum or buzz, that would suggest DC is not flat enough, or small distorsions of video output exist, etc.

If it doesn't show any problems - don't fix it.

 

[AmiNeo]

I actually have a PSU here which caused me a lot of trouble with that very same thing. I had a few motherboards and I was blaming the caps on them, replacing them over and over, STILL BUZZ IN THE SOUND! ... Wasn't until zetr0 or merlin said something that it clicked! THE PSU!

The aftermath from that resulted in a lot of Zetr0 pestering! lol

---------- Post added at 12:31 ---------- Previous post was at 12:29 ----------

Guys, is it possible to test this without opening it atall with a multimeter? I'd imagine so but I'm not sure how you'd go about it...

Yes
You could measure the AC component within DC output while in full operation. Higher values sugest that caps may be dry.
The thing is... You don't know what nominal values are, so...

There are other methods.
- You can easily check for leaking caps by visual examinantion.
- You can check if audio is clear wiht no brum or buzz, that would suggest DC is not flat enough, or small distorsions of video output exist, etc.

If it doesn't show any problems - don't fix it.

And we may not know what nominal values are but wouldnt someone more experienced know? Like Zetr0?

---------- Post added at 12:56 ---------- Previous post was at 12:31 ----------

'If it isnt broke dont fix it is a rule I can understand' but I'm sorry, as for "if you have to ask, you should not to do it!" thats the worst advice ever... Okay if something is dangerous I might agree with it for some people but generally, if people dont ask and try things for themselves we'd all just be a bunch of lazy no hopers that gets other people to do things for them and never learns anything for themselves.

How can you learn anything if you dont ask and try it for yourself when you're equipped with knowledge? We're not born with instincts to repair stuff. If you want to get good at doing this stuff you have to start from a position of knowing nothing like everyone else.

 

[Elerion]

@AmiNeo:
You can check some measurements from my A4000 psu before and after caps replacement here. But these are also just some numbers, not a benchmark.

The "if you have to ask, you should not to do it!" is not a general rule, but applies in this case. There are too many questions that should be asked. From: What kind of tools I need?, How to remove charged cap?, Ground the board to soldering iron or not?, etc, etc.

And even after everything is done correctly, shit might happen. While returning the screws, one might slip, make a short circuit, and cause explosion somewhere. So it is definitely a job for someone with more experience.

It's OK if you are ready to accept a few destroyed PSU's, as a part of your electronics training.

 

[Jumping Anaconda]

I was only going to do a visual inspection of the capacitors. If it is not likely to be safe after 10 days, if I leave it another couple of weeks, would it be likely to be discharged?

 

[AmiNeo]

@AmiNeo:
You can check some measurements from my A4000 psu before and after caps replacement here. But these are also just some numbers, not a benchmark.

The "if you have to ask, you should not to do it!" is not a general rule, but applies in this case. There are too many questions that should be asked. From: What kind of tools I need?, How to remove charged cap?, Ground the board to soldering iron or not?, etc, etc.

And even after everything is done correctly, shit might happen. While returning the screws, one might slip, make a short circuit, and cause explosion somewhere. So it is definitely a job for someone with more experience.

It's OK if you are ready to accept a few destroyed PSU's, as a part of your electronics training.

Yup. For a complete novice im in complete agreeance, which is why I suggested starting on some smaller caps and learning to discharge those first to get used to the job without the element of danger if you do screw up. But to be fair, even the best screw up and destroy the odd peice of hardware occasionally. It's nothing to feel bad about. Just gotta keep yourself safe.

---------- Post added at 13:44 ---------- Previous post was at 13:36 ----------

I was only going to do a visual inspection of the capacitors. If it is not likely to be safe after 10 days, if I leave it another couple of weeks, would it be likely to be discharged?

It depends on the capacitors, I've heard of caps holding charge for months but I dont know how long the Amiga PSU caps would hold charge. They can pick up residual charge after theyve discharged too so ideally you'd manually discharge them prior to working.

 

[Elerion]

I was only going to do a visual inspection of the capacitors. If it is not likely to be safe after 10 days, if I leave it another couple of weeks, would it be likely to be discharged?

Best way to discharge it is to plug it in to Amiga, (without pluging in the 230V) and leave like this for a few minutes.
Then plug it out and short circuit all pins of the power connector to ground pin, one by one. (sparks are normal, and they should not destroy anything at this point.)

Some charge will be left in PSU, but it will be much better then just waiting.

Largest high voltage caps in the psu will be left charged, because they are separated from the rest of the circuit. You should remove and replace them first, making sure polarity is correct.
When they are out, you can discharge them by shorting them out, but do not do this while they are on the board.

Be careful that PSU is at all times removed from the 230V current until you reasamble it, use insulated tools, do not ground the soldering iron, and the experience should not kill you.

There! But if something explodes still, don't say you have not been warned.

 

[AndyLandy]

I was only going to do a visual inspection of the capacitors. If it is not likely to be safe after 10 days, if I leave it another couple of weeks, would it be likely to be discharged?

Best way to discharge it is to plug it in to Amiga, (without pluging in the 230V) and leave like this for a few minutes.
Then plug it out and short circuit all pins of the power connector to ground pin, one by one. (sparks are normal, and they should not destroy anything at this point.)

Some charge will be left in PSU, but it will be much better then just waiting.

Largest high voltage caps in the psu will be left charged, because they are separated from the rest of the circuit. You should remove and replace them first, making sure polarity is correct.
When they are out, you can discharge them by shorting them out, but do not do this while they are on the board.

Be careful that PSU is at all times removed from the 230V current until you reasamble it, use insulated tools, do not ground the soldering iron, and the experience should not kill you.

There! But if something explodes still, don't say you have not been warned.

I don't think you can say fairer than that. As it happens, I'm fairly cavalier myself, I've been inside a few ATX power supplies over the years and have never had a problem. Just show this stuff the respect it deserves and you'll be fine!

 

[Jumping Anaconda]

If it is that dangerous I will not take the risk. I probably need to have someone replace the capacitors in the A1200 anyway. Maybe someone will be able to look at the power supply at the same time?

---------- Post added at 14:18 ---------- Previous post was at 14:17 ----------

BTW, thanks for all the replies and information.

 

[AmiNeo]

Better yet. Find yourself a converted ATX PSU, more juice plus itll be way newer so lastability shouldnt be a problem. Caps in your system mightnt need replacing just yet atall.

If you have sound issues, it could be the PSU or the caps on the motherboard.
Trying the miggy with a converted ATX PSU would be a good test as the sound should be perfect using that if your PSU was letting you down.

 

[Jumping Anaconda]

I think the PSU is a good place to start, particularly as I am having trouble with expansions and hard drives in my A1200. I'd liek to trace faults first though, rather than just starting changing things wholesale. I am guessing that the A1200 capacitor replacements need to be done sooner or later though, although I do have a UK made Commodore machine. Maybe this increasingly the likelihood of higher quality components being in place?

 

[Elerion]

I agree. Both on a place to start and the need to replace caps.
But don't think that A1200 made in UK is somehow special. All A1200's and A4000 amigas have cheap Taiwanese caps installed. All of them will start to leak withnin 10-20 years or so. Japanese solid caps that will not leak look a bit different, and I didn's see any Japanese caps in any A1200 or A4000 Amigas. Not even in ones made in Japan.

 

[rkauer]

People, please quit scaring JA!

All mains capacitors on PSU must have a discharge resistor in parallel. After a couple of minutes the capacitors will be flat ( = no voltage at all = 0 = zero). Those are the biggest units inside the PSU.

Just discharge the low-voltages units plugging-in the PSU to the Amiga while the PSU is disconnected from mains and all is sorted.

Beware the polarity when replacing the cappies. That's all.

 

[AndyLandy]

People, please quit scaring JA!

All mains capacitors on PSU must have a discharge resistor in parallel. After a couple of minutes the capacitors will be flat ( = no voltage at all = 0 = zero). Those are the biggest units inside the PSU.

Just discharge the low-voltages units plugging-in the PSU to the Amiga while the PSU is disconnected from mains and all is sorted.

Beware the polarity when replacing the cappies. That's all.

Oh wow! That makes things a lot safer and easier. For me, I'd still practice caution... just in case.

 

[Tajmaster]

Thats super advice rkauer Nice and crystal clear for novices

 

[AmiNeo]

People, please quit scaring JA!

All mains capacitors on PSU must have a discharge resistor in parallel. After a couple of minutes the capacitors will be flat ( = no voltage at all = 0 = zero). Those are the biggest units inside the PSU.

Just discharge the low-voltages units plugging-in the PSU to the Amiga while the PSU is disconnected from mains and all is sorted.

Beware the polarity when replacing the cappies. That's all.

Oh wow! That makes things a lot safer and easier. For me, I'd still practice caution... just in case.

Okay well I had no idea it was compulsary to have a discharge resistor in parallel on all PSUs. Just going by what I've been taught as an IT Tech and the warning labels on all the PSUs.
If you're certain the old miggy PSUs are that safe I have a few projects I may now feel easier going ahead with

 

[Justin]

oh FGS!!! just give the caps a test lick!! go on you know you want to

 

[AmiNeo]

Oh alright... :shock: :woot:

 

[cosmicfrog]

Licking caps is the only way I know how to jump over small buildings
extra boost to my froggie legs

 

[AmiNeo]

Hehe, bloody fast way to cook frogs legs too