A4000 boot failure

[Kin-Hell]

Shamus...check your PM's mate!  :-)

[Shamus_]

Have done and just did etc....  :lol:

I'm just about ready to have my 4000 put down if the psu thingy isn't the cause of the problem, even though I can't see anything obvious wrong with it. I gave the psu a bath the other day to clean the accumulated crud off the various bits inside but to no avail. Looking to grab another psu off ebay. A spare wouldn't hurt....

[CLS2086]

Final solution : send it to repair at AmigaCenter

[Flash]

Hi,

From a recent experience from one of my A1200's, Ihad a failure in one of the 3.1 rom chips which produced a similar occurrence, I tried a downgrade to 3.0 roms and my computer booted no problems. Therefore check your rom chips are correctly seated, especially as they tend to draw out from the socket holders over time.

Yours Flash      :idea:

[Shamus_]

CLS2086 wrote:
Final solution : send it to repair at AmigaCenter

It's not a bad idea but the Heap-O-Crap™ would cost more than it's worth to freight to France and back from Oz.  I should have a new PSU for it in a week or so. If that doesn't work I might just scrap it as parts. :-(

[Shamus_]

Flash wrote:
Hi,

From a recent experience from one of my A1200's, Ihad a failure in one of the 3.1 rom chips which produced a similar occurrence, I tried a downgrade to 3.0 roms and my computer booted no problems. Therefore check your rom chips are correctly seated, especially as they tend to draw out from the socket holders over time.

Yours Flash      :idea:

A good idea but it's not the problem. If you look through the thread I've swapped out the motherboard with others and got the same result. All chips on all boards are properly seated and the PSU is the only component that hasn't been changed.

[Zac67]

A word on electrolytic capacitors: Their tops must be absolutely flat. When they break the top bulges out, not always do they leak and very rarely rupture.

Open the PSU and check that for bulged caps, too. Don't touch anything inside, there may be hazardous voltages, even when disconnected from mains!

Check PSU voltages (under normal load), there shouldn't be more tolerance than 5%. Also try the multimeter set to AC to check for ripple in the voltage - more than ~100 mV isn't to good either (vary CPU load, floppy, hard disk access while doing that).

[Homer]

Hi Shamus, did you try leaving the molex in the hard drive but taking out the IDE cable before booting up? That should load the psu without bothering the IDE bus........
Do let me know what happens  :-D

[Shamus_]

Zac67 wrote:
A word on electrolytic capacitors: Their tops must be absolutely flat. When they break the top bulges out, not always do they leak and very rarely rupture.

Open the PSU and check that for bulged caps, too. Don't touch anything inside, there may be hazardous voltages, even when disconnected from mains!

Check PSU voltages (under normal load), there shouldn't be more tolerance than 5%. Also try the multimeter set to AC to check for ripple in the voltage - more than ~100 mV isn't to good either (vary CPU load, floppy, hard disk access while doing that).

I'll have to get a mate of mine to do this as my skill with electronics is only surpassed by my skill as a photographer. .. which I will demonstrate shortly. The tops of the capacitors are all dead flat. No bulging etc. The one thing I did find after a close look was a white, dry residue on one of the larger capacitors. I have no idea if it was always like that or it's the source of the problem. Have a look for yourself here:

http://users.tpg.com.au/adsldxhe/piccy.jpg

[Shamus_]

Homer wrote:
Hi Shamus, did you try leaving the molex in the hard drive but taking out the IDE cable before booting up? That should load the psu without bothering the IDE bus........
Do let me know what happens  :-D

Heya mate.

I did try that but nothing changes. Remember that I've tried 3 different motherboards and they all do the same thing... that is if I pull all the RAM out, I don't get a green screen (CHIP RAM failure) when it tries to boot. The only things plugged in are the PSU, m/board and o4o card. That's it and the PSU is the only thing that remains constant.

[rkauer]

Caps can die with no external signals of their deaths.

 They simply "dries" inside and then no more do their job (filtering, decoupling, etc).

 Your best bet is just change all of them OR put a new AT PSU (from a peecee). It's an easy hack to do in an A4000.

[Shamus_]

Hoping to pick up another PSU next week. For someone with no electronics ability at all, how difficult is the hack? Is there a schematic around somewhere that I can toss at a mate of mine who understands it?

It's infuriating. My Cybervision card is sitting in its box unopened. I've also got a scsi card, network card and extra drives ready to go in once it's up and running. I dug up an old hub with a BNC port on the back so the Ami can slot into the rest of my network. B*stard of a thing.