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AuthorTopic: "New" A4000 power problem  (Read 1221 times)

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Offline stopthegop

"New" A4000 power problem
« on: November 30, 2006, 03:49:52 AM »
Hello
Just got a "new" A4000 desktop off craigslist.  It was advertised as non-working, good for parts only.  Paid a whopping $30.  The machine is actually complete and in decent physical condition incredibly, with no battery leakage.  It has a power problem though and I just wanted to fish for ideas here before I get too far on the wrong tangent.  It powers up for maybe three seconds, then just shuts down.  The fans spin, but not as fast as you would think.  When it gets power it sounds very "weak", then just shuts itself off.  The PSU is ok, I think.  5v and 12v output are ok.  115vac input is good, too.  Its got a 3640 installed and thats it.  Any suggestions?
Primary:
A4000T. Phase5 PPC604e-233mhz/060-66mhz. Mediator, Z3 Fastlane, Voodoo5, Delfina, X-Surf, AD516, Peggy Plus.

Collection:
A4000D, A1200, A500, Milan060 (Atari clone), Atari MegaSTE, Atari TT030, C64, C128, Mattel Aquarius, (2) HP Jornada....
 

Offline pedro7

Re: "New" A4000 power problem
« Reply #1 on: November 30, 2006, 11:59:03 AM »
What happens when it shuts off, does everything lose power ie fans/drives spin down completely, LEDs off? Have you tried monitoring the PSU voltages as this happens?
If you tested the PSU without anything connected to it might be that it gives the correct voltages when no load is on it but when a current is drawn the voltages drop. I'd test it with another PSU if you can.
 

Offline _ThEcRoW

Re: "New" A4000 power problem
« Reply #2 on: November 30, 2006, 03:09:28 PM »
It seems a psu problem. Like pedro said, when power is sucked then maybe it can't keep the voltage needed to the system to be stable, so therefore it shuts off.
Amiga 1200 desktop. Apollo 030/50 Mhz 8mb ram + ClassicWB + Wb 3.1
Amiga 500 + ACA500Plus + 16gb CF | ECS Power!!!
C64 DTV + Keyboard mod. Waiting for a 1541 disk ve...
Mac Mini G4 1.42Ghz 1gb OSX(tiger)/Morphos 3.7 Registered
C64mini + usb drive with loads of games...
 

Offline tonyvdb

Re: "New" A4000 power problem
« Reply #3 on: November 30, 2006, 03:36:46 PM »
Just replace the power supply with an ATX one and get the adapter from Amigakit. That should solve the problem.
Amiga 2000HD Indivision ECS
Amiga 4000D towerised OS 3.1 and 3.9 on CF cards
Indivision AGA, Mediator 4000
Video Toaster 4000 Flyer v4.3 Millenium.
202gig of video drive space & 5gig audio.
 

Offline stopthegop

Re: "New" A4000 power problem
« Reply #4 on: November 30, 2006, 04:41:01 PM »
I don't think it the power supply.  I swapped with a known good PSU.  Same problem.  Well, not exactly.  Now I get a bright green display before it shuts itself off.  Previously it just shut itself off after 3 seconds.  Now it stays on for perhaps 10 seconds, displaying bright green from the AGA port immediately before shutting itself down.  Bad memory?  Zorro problem?  AGA problem?  What would cause it to just lose power like that besides the PSU?
Primary:
A4000T. Phase5 PPC604e-233mhz/060-66mhz. Mediator, Z3 Fastlane, Voodoo5, Delfina, X-Surf, AD516, Peggy Plus.

Collection:
A4000D, A1200, A500, Milan060 (Atari clone), Atari MegaSTE, Atari TT030, C64, C128, Mattel Aquarius, (2) HP Jornada....
 

Offline pedro7

Re: "New" A4000 power problem
« Reply #5 on: November 30, 2006, 05:40:32 PM »
Hmm, strange.
Maybe there is a short circuit between ground and one of the power lines on the circuit board. This could explain the known good PSU lasting longer, the other one could have been damaged by repeated short circuiting. I'd suggest using a replacable AT/ATX PSU for any more tests.
Check with a multimeter for any shorts between the power lines. I think I read somewhere that the a4000 can have problems with the pins from the power connector on the circuit board underside touching the case and shorting. Is there any physical damage to the board anywhere? Bent pins? Pins touching in the zorro connectors? fried components or heat damage from shorting?
It can't hurt to take out the zorro backplane and everything else non-essential and reseat chips and ram.
 

Offline AmiSake

Re: "New" A4000 power problem
« Reply #6 on: November 30, 2006, 05:51:08 PM »
It's been  a while since I used my Amiga but I seem to remember that during POST the screen colors will tell you what's wrong:

see this link:

http://www.amicue.org/TechStuff/amigaboot.html
 

Offline Tomas

Re: "New" A4000 power problem
« Reply #7 on: November 30, 2006, 05:51:42 PM »
Try removing any addons..