A4000 gone dead!

[dvvrue95]

Hi there,
my A4000 recently obtained from Ebay has died on me.
I was installing a 2nd (replacement) drive and decided to use Disksalv 'cause of the problems (errors) with HDInstall
so I left the machine on overnight.
On my return the machine power light was on but not much else, I had powered off monitor last night but when I switched it on it was just a bank screen.
I tried a soft reboot but inspit of some hd activity and hd light flashing no joy and then I noticed the powere light was flashing. So I powered off and disconnected both drives and powered on this time I just had the green power light flashing?? Any ideas what it could be. I dont think it is anything to do with hd's.I get a blnk screen no
no WB 3.0 insert disk icon.

thanks, Ian

[CLS2086]

Hi,
test your PSU, and send your motherboard to Amigacenter in France. try to reseat your CPU card

[doctorq]

Try stripping the computer to the bare bones, so only motherboard, daughterboard and CPU card is installed. Power up, and wait 2-3 minutes to see if you get the purple boot screen (it takes a while to get to the boot screen since the computer can't find neither floppy nor hdd).

Try giving all socketed chips a firm push, and make sure the CPU card is firmly inserted.

[alexh]

A continually flashing PSU light (audio filter on, audio filter off) with no GURU MEDITATION usually means a crash during kickstart execution... check your kickstart ROMs make sure they are seated

[tonyvdb]

Have a look at the battery, If it has any corrosion on or around it remove it imediatly (the 4000 dosent need it to work) clean up the board around the battery with a q-tip and some rubbing alcohal and check to see if the traces are broken in that area.

[dvvrue95]

Hi thanks for ALL feedback,

A.
I unplugged psu from motherboard and
measured :-
-17v on Red (-12v)
+6.8v on Orange (+12v)
+5.04 on Yellow (+5v)

all open cct. i.e. nothing connected to psu
can anybody please check their setup I have shown what I think are the correct voltages in brackets, WOULD A DODGY +12V rail cause these problems? If I'm correct
it looks like psu has gone down.PLEASE ADVISE.

B.
I stripped everything down to motherboard and then re-seated socketed chips, daughterboard, and A3640 board. Reconnected psu and switched on (without hd's or fd connected initially I got a guru meditation (s/w error) message followed by purple screen, so I switched off reconncted fd and switched back on this time just a flashing power led! oh and the fan in the psu runs - since then just a flashing power led and fan running.

C.
IWhen I first got the machine I stripped the battery out since it looked in a bad way, have cleaned up as much as possible and replaced with a NiMh battery but clock settings still does not seem to hold up that was after a couple of days of having machine on charging new battery.

[Homer]

Can you check those supply voltages with the motherboard connected to show us on load voltages ? Otherwise can you get hold of a spare pc AT or ATX psu to rule that out ??

[Boot_WB]

dvvrue95 wrote:
Hi thanks for ALL feedback,

A.
I unplugged psu from motherboard and
measured :-
-17v on Red (-12v)
+6.8v on Orange (+12v)
+5.04 on Yellow (+5v)

Seems rather odd that both 12v rails are out by +5v.  Are you certain you were measuring the voltage between +12 and earth, -12v and earth?
Apologies if this seems insulting, but it is a very strange reading.
It would be explained if you were measuring voltage between +12v and +5v (=~7V), and -12V and +5V (=17V).

If these strange readings are indeed correct I would not plug that psu back into my a4000 - or back into ANYTHING.  The +6.8V will just underpower things, but the -17V could burn tracks clean off the board.

[alexh]

dvvrue95 wrote:
I got a guru meditation (s/w error) message followed by purple screen

http://www.amiga.org/modules/xoopsfaq/index.php?cat_id=3

[dvvrue95]

Hi,

OK voltages measured with psu connected to MB, but no hd or fd connected :-

ORG +7.11V
RD  -17V
YL  +4.92V

all measured with reference to GND.

Having done that test again comments about not reconnecting psu to anything noted!

thanks again

Will try to track down a spare AT/ATX psu in the next few days to eliminate psu.

[Tomas]

Check that all chips are placed properly and also check that the battery has not leaked over the board.

I am no expert, but those voltages also seems pretty bad.. Could definitely be a reason as well.

[MigaMan]

Well the +12 and -12 lines are probably for op-amps and comparator cirucits in the video amp. circuits.  If they aren't reading right, then that would cause a video problem.  Your hard drives run on the 5V line so that shouldn't be a problem.  Are you checking the voltages out of the power supply with the GND on the power supply cable?  Also, how many cables go into the connector?  It could be possible that each power line has its own GND line associated with it.  Then you would need to read between these two to get the correct voltage out.  

[metalman]

dvvrue95 wrote:

OK voltages measured with psu connected to MB, but no hd or fd connected :-

ORG +7.11V
RD  -17V
YL  +4.92V

all measured with reference to GND.

GND = Black?

The harddrive uses both +12vdc and +5vdc
Don't use that PSU anymore!
The PSU needs repair, trim pot(s) on the 12v side are suspect

[dvvrue95]

Amiga Ground is Blue not Black.......
OK so I'm an idiot!

It was only when I was trying to match up the A400 psu leads with a "borrowed" ATX psu that I realized my previously silly mistake in measuring the voltages from the A4000 psu.

The A400 uses a power good indicator (logic 1, which I have taken as +5volts) which comes out on the Brown wire, previously I hade been looking at some (duff) info which suggested that was Ground, in fact there are two Blue wires which are Ground.
If I measure using this convention I now read the following :-

Gnd (Blue) Red    (-11.95)
 "     "   Orange (+11.48)
 "     "   Yellow ( +5.02)

also if I measure Gnd (Blue) Brown (+4.95), which I guess is the logic 1, power good indicator from the psu.

All above measured connected to mb without hd's or fd connected.
I have reseated all socketed chips, including removing and refitting the 3.0 roms, if I switch on now I get the flshing green power led which seems to flash quickly for five or six times, pauses and then repeats five or six quick flashes accompanied by a Yellow screen which displays twice and then screen goes blank.

I think (but I'm not too sure after the voltage fiasco)a Yellow screen is supposed to indicate a "68000 detected h/w or s/w error" ---- whatever that means. http://www.amiga.org/uploads/smil402e47bbde2c2.gif
http://www.amiga.org/uploads/smil402e47bbde2c2.gif
I have managed to "borrow" a ATX psu and will be getting a converter cable later in the week so will try to use that to eliminate the A4000 psu.
Sorry for the naff readings at the start of this article, hopefully the ATX psu will do the trick.
Thanks again for all your contributions,
Ian