User avatar
grshaw

Posted Wed Jan 01, 2020 10:02 am

I have an A2000 PSU which I bought from eBay. I wonder whether it needs to be recapped. Certainly, it's not behaving like I expect it to. The situation is complicated by the fact that I am testing it whilst it is not connected to an A2000. I just have it sitting on my workbench, plugged in to the Mains. The symptoms it has are as follows:

  • The fan does not spin up every time that the PSU is switched on. Strangely, it always seems to start spinning on the third on / off cycle of the power switch on the PSU.
  • The voltages are way off from what they should be. I am expecting +-5V and +-12V. In fact, I am seeing less than 1V on pretty much all the wires. I am testing with a standard Multimeter, inserting the probes into GND and the relevant holes in the main Power connector.
So, I am wondering, is the PSU faulty and perhaps in need of recapping, or is this strange behaviour resulting from the way I am testing it? Perhaps the PSU detects that there is no load and goes into some kind of failsafe mode?

NB - I replaced the fan today with a Noctua silent fan in the hopes that this would fix the first issue. It runs much more silently now - but the intermittent behaviour with the fan not spinning up remains unchanged.

Any ideas would be much appreciated.

User avatar
intric8
Seattle, WA, USA
Website

Posted Wed Jan 01, 2020 2:52 pm

I've never seen an A2000 fan behave like that, plugged in with load or out on the floor. They are built like tanks and I've never had to recap any of mine, but of course it's certainly possible. Something odd is going on there for sure.

PSA
If you take the thing apart, be really careful if you give the thing power. Those really large caps - almost the size of C-batteries - can kill you.

User avatar
grshaw

Posted Thu Jan 02, 2020 6:09 am

Thanks for the advice.

I will try recapping and see if that resolves the issue ( because I cannot think of anything else to try ).
If you take the thing apart, be really careful if you give the thing power. Those really large caps - almost the size of C-batteries - can kill you.
I know the ones you mean. I bought a capacitor discharging tool specifically for this purpose. Certainly sound advise though.

User avatar
A10001986

Posted Sat Jan 04, 2020 2:39 am

I had all my A2K power supplies recapped. If you can actually see your floppy drive working on the screen (flicker, light-dark-distortions), it's definitely about time.

Also, look at the big caps. Some models came (I forget which ones) with cheap ones, these are prone to leak. If they show a bulge, get them out.

User avatar
grshaw

Posted Sat Jan 04, 2020 11:20 am

I can't see any bulging. To be honest, I am not at all sure that it's the capacitors that are the problem. I am not too clued up on these PSUs, so I don't really know what else to fix. I am planning to try swapping the caps. If that does not fix the problem then I may have to give up on it and go down the road of putting an ATX power supply in there instead.

User avatar
Christian

Posted Sun Jan 05, 2020 2:33 am

Test it with a load such as an old hard disk. Without a load, most big box Amiga power supplies will shut down. Also the Elec&Eltek or Phi Hong A2000 power supplies shut down if the fan doesn’t draw a minimum load. I don’t think that is the case with the Liton A2000 power supplies.

User avatar
grshaw

Posted Sun Jan 05, 2020 6:35 am

That's a good call. It's a Phi Nong PSU.

With an Amiga Floppy Drive plugged in, I see values much nearer to what I would expect. However +5V is actually taking the value +6.1V. Additionally, Orange, which should be +12V is way too low, taking the value of only 7.2V. I am now thinking that a recap may in fact fix this issue. Still not sure, but at least the values are vaguely in the right ballpark now, which suggests that it may be some caps which are not behaving as they should be.

Thanks.





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