Think my A4000 is dying. Possible PSU problem.

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daveh35

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AmiBayer
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Hi all, would appreciate some advice.

My A4000D which has always worked perfectly has recently developed a fault when I power it on. For the first 10 - 20 seconds, I am getting no fan noise from the PSU, a regular clicking from the disks as they seem to try to spin up and fail and a flashing power light. After those initial problems, the fan will suddenly start and the machine powers up and works perfectly for hours. The problem seems worse if it has been switched off for a long time. If it is running and I power it off and back on again immediately it starts up fine.

What do you think? Power supply problem? I am seeing voltages of 4.9 and 11.5 with the machine running and measuring at a spare molex connector. It has the original Skynet 145W psu.
 
maybe a capacitor problem?

as you are getting this problem in the first few seconds of boot time.
 
Yes it does sound like the PSU; unless you find an electronics technician to repair it, I'd look for a new one
 
Indeed the PSU have some about-to-die capacitors on it.

If you have not electronic skills, ask a technician to replace all those little things for you or grab a converted ATX power supply.
 
Thanks for the replies which confirm my initial thoughts. I'll open it up and see if my soldering skills are up to the job but most likely I'll have to find someone to do it for me.
 
I highly suggest not to power up your A4000 until the PSU is fixed/replaced.
What you're describing can cause serious damage to the hardware!
 
lostrego said:
Yo may find this thread at the photo booth section very useful if you decide to replace the Skynet's Caps:

https://www.amibay.com/showthread.php?t=10132

Along it You'll find also some google docs tables with the needed capacitors.

Hope it helps :) .
Click to expand...
Wow, that's all very useful. Thanks for pointing it out and thanks d0pefish for putting all that information together.
 
I have dismantled the PSU and can see one capacitor which looks to have been leaking. All others look ok but I'm going to go ahead and replace them all.

While I have it in pieces I'm also going to get a quieter fan but I'm wondering what flow rate I should get. For a 12V 80mm fan I can get 0.5 to 1.25 cubic metres per minute with a noise level of 12 to 35 dbA. I have no idea what dbA the current fan is, I just know it is very noisy and I want it much quieter.

Any suggestions for a suitable fan?
Thanks.
 
im a bit worried about the fan noise problem because i see peaple talking about slowing the fan down(not the same as getting a fan thats has more blades and is less noisy by design)
im not saying this is what you may/maynot do i just think its worth a mention.

the reason im saying this is beacause the power supply is the air flow system for these machines slowing the fan down may make the system hotter inside because the fan isent moving the air fast enough.

ok its fair to assume not all big amigas are brimming with hardware,but you see what im saying.

i would just get the same size fan thats less noisy and equal or more air flow than the original one or has the same airflow but with less rpm's.
 
roy_bates said:
i would just get the same size fan thats less noisy and equal or more air flow than the original one or has the same airflow but with less rpm's.
Click to expand...

Totally agree with everything you say. I have no intention of reducing the noise at the expense of less cooling. Problem is I have no idea of the spec of the current fan in terms of airflow, rpm or noise level so choosing another is a bit tricky, hence the question.
 
Capacitors now replaced in the PSU and it's working perfectly again. I used d0pefish's excellent post and list of capacitors and replaced the same ones he did. Voltages are now 5.04 and 12.03. Not quite the 12.57 d0pefish shows in one of his photos but everything is running ok so I guess it's not a problem.

Haven't bought another fan yet as I was waiting to make sure the PSU was ok first.

Thanks again for everyone's advice. The A4000 lives again :D
 
Nice to hear that :thumbsup:

For the fan/airflow thing, the main problem with the Skynet PSU type is more related to the air intake "grille" and the rear vents of the PSU case that impede a good air flow, modding it is up to you.

I'd consider first what kind of gear are you running on that 4000, say that if you are running an stock 3630 plus some simple zorro gear, then something equal to the stock ventilation should be enough, but if you are running there a more complex setup (say CSPPC plus a mediator/grexx + some "hot" PCI GFX card) then improving the air flow is a must, also a more powerful PSU solution is desirable.
 
Or at least a decent airflow modification.

The best mod I saw to this day is sawing off the grill vents in the PSU and replace it with metal mesh and a rubber border to have a nice finish. Lots of air moving with little aerodynamic resistance.
 
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