Killer A3000!!!!

Oh dear,

my luck with Amiga hardware is well on form.

I have just had an a3k refurbished - new caps installed on it and the daughterboard etc.

Received the boards back, installed it all with a Cybervision 64 gfx card and installed OS 3.9.

All working well. After about 15 minutes of usage, suddenly the pass through part of the Cybervision 64 develops a fault and starts showing everything in shades of red. Weird.

I then noticed the chips on the Cybervision 64 getting very hot. But, the RTG output was still perfect.

Left it running for about 2 hours, came back - the Cybervision 64 is now completely dead. Very weird.

Pulled it to get it sent away and looked at. Installed my Toccata sound card. Set it up. All good.

Hour later, the Toccata is no longer working. Will not even appear in the Board diagnostic start screen of ks. Very very weird.

Hmmmm, wondering if the daughterboard is outputting too high a coltage and killing boards, so I plugged in a "disposable" board. A Vlab Motion board. It shows up working... but the chip on board starts getting VERY hot (whilst it is not even working, nor even software installed).

Pulled board before it could be completely destroyed.

Any ideas?

Quote:

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Originally Posted by abraXXious

Hmmmm, wondering if the daughterboard is outputting too high a coltage and killing boards, so I plugged in a "disposable" board. A Vlab Motion board. It shows up working... but the chip on board starts getting VERY hot (whilst it is not even working, nor even software installed).

Pulled board before it could be completely destroyed.

Any ideas?

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Any measurements of +5V +12V and -12V?

We are talking about 15+ years hardware, so better to check power first by connecting spare HDD (with bad secors or so) to PSU and check voltage. This is my standard porcedure when I test unknown PSU.
And remember - please DO NOT switch on PSU witout load (1 or 2 spare HDD will do the job).

Update!

I have noticed that a few chips on the a3k mb are getting very hot, you can touch them, but only just.

These chips are the small ICs - U705, U715 etc etc.

The ram chips and a few others are getting warm, but only warm. These other ICs, about half a dozen are getting VERY hot.

Is this normal for an a3k?

It's normal for the PAL chips (U202, U714 etc) to run hot. Ideally, they should have been replaced with cooler running GAL chips if you had your board refurbished. U705 & U715 are just logic chips,
and shouldn't run hot though..

You need to shut it off until you have a multimeter to test your voltages from your power supply, I'm going to guess your +5 is over voltage.


Later,
dabone

@ abbraxious

Spare this board from the hammer of the skip, for the love of God... I'm sure that with help from the members on here, it can be fixed... just don't kill it...

U704 and U254 get especially hot. These look like standard logic ICs (to me) so that does not bode well. Althought the system appears to function perfectly (despite doubling as a space heater :)), apart from the daughterboard from hell, I will shut it down to prevent any possible heat related damage until I can check the voltages coming from the psu.

Thanks for your help guys.

@Abraxxy

it would seem that you have a spikey psu - as other have said - get a multimeter - without this you might as well be a blind man atempting to do a rubix cube!

unplug the A3000 mobo - there's no need for it to be suffering such torture - load up a couple of 3.5" HDD's and get the multimeter out... test over 45 minutes to an hour -

1. test on start-up both +5, +12, -12, -5 (bolded are important!)
2. test at 10 or 15 minute intervals
3. repeat tests at least 3 times

I suspect you -5v and or +5 is running rampant as dabone states

Interestingly enough the A3000 is the only Amiga that uses -5 volts

The upper limit of the voltage should not be any more or less that 5%

so a 5V rail should give you (maximum limits)

LOWEST = 4.75v
HIGHEST = 5.25v

if you get anything less or greater than these your PSU is pooped!

Personally I would hack-in an ATX PSU =)

Hmm, strange you only have problems with cards. The doughter board deasn't change any voltage, or is that false? If the PSU is bad and gives too much power, also the A3000 motherboard could have been damaged because the chips are also running at 5 V.

Also too less power could be the problem. So, the cards can't run how they should. If you upgrade with more cards, it needs more power, so the PSU is over-used (old PSUs often get that. I had an A2000, hooked up a turboboard and after 10 minutes running, it got some failures in graphics, later the PSU was dead completly).

Also you can try clean the contacts, if that could be the fault also, but not sure if that has something to do with your problem.


What BUSTER do you have? Some cards/combinations run with buster 11 only. If you have buster 9 that also could be the Zorro problem.


That just ideas, what I would check. Hope you can fix it and find out. Tell us what was wrong, thanks,

gehtjanx

Thanks for the tips Zetr0 - will dig out my Multimeter in the morning and post the results.

Hi gehtjanx. I think you may have misunderstood my original post. The a3000 has actually KILLED two zorro cards. They are actually dead now, fried even. They got very hot, then dies. In the case of the Cybervision card, bit by bit. I have tried them in two other good machines and they do not even appear in the early boot screen under board diagnostic. :(

Will post results of psu testing shortly.

---------- Post added at 02:14 ---------- Previous post was at 02:12 ----------

Out of interest, how far over voltage does the +5 rail need to get before it start killing things? Im used to electronics that can handle +30% voltage before you run the risk of damage. Obviously amiga gear is more sensitive to voltage. That is of course it is not uncommon for something like the +5v line to go as high as say 6.5v on a defective psu.... is this possible?