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Old 02 October 2018, 16:00   #1
reflex
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Is this Amiga 4000 CPU slot faulty?

Hello friends,

i have the following problem with my beloved amiga 4000.
I have a micronik full tower with Mediator PCI board, the computer works ok, but after some time the CPU board seem not to make proper contact anymore.
In fact it could happen that at a cold boot the green light doesn't flash, remaining at the low green color, the screen stays black, the floppy drive doesn't click.
If I unplug the CPU board then plug it on again it works ok for a while that the problem comes out again.
Sometimes it happen even while the system booted and i am using the computer, amigaOS freezes and if I make a warm reboot the green light acts the same (doesn't flash and stays in the first low stage).

It cannot be the CPU board as it makes exactly the same both with the CSPPC and the 3640 original board.

Last year the mob had some repair (new capacitor, 64mb hack, clock battery leak) and i asked the repairer to change the CPU slot (so now it should be almost brand new) but the problem come back and was never truly solved.

What could it be? Any suggestion how to solve it and who can repair it once for ever?
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Old 02 October 2018, 17:49   #2
elenachen
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Hmm, could be the Slot or a cold solder joint. Try inspecting the backside of the connector with a magnifying lens. Is you PSU ok?
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Old 02 October 2018, 18:19   #3
Hedeon
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Using risers which you can screw tight instead of the plastic ones?

I had something similar and even the weight of the SCSI cable would sometimes just dislodge the CSPPC to the point I got a black screen. Reseating would help everytime. Now the board is screwed in place.
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Old 02 October 2018, 20:49   #4
nexus
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Quote:
Originally Posted by elenachen View Post
Hmm, could be the Slot or a cold solder joint. Try inspecting the backside of the connector with a magnifying lens. Is you PSU ok?
he should use a multimeter not a magnifying lens
cant hurt to go over all with flux and reflow them
but i would also make sure everything is clean
get all contacts both sides well with alcohol

if the socket was replaced maybe whoever didnt do a great clean up and flux got on pins

if you have the board out of the case you can check continuity from mobo to accel while its mounted
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Old 03 October 2018, 00:33   #5
elenachen
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Quote:
Originally Posted by nexus View Post
he should use a multimeter not a magnifying lens
cant hurt to go over all with flux and reflow them
but i would also make sure everything is clean
get all contacts both sides well with alcohol

if the socket was replaced maybe whoever didnt do a great clean up and flux got on pins

if you have the board out of the case you can check continuity from mobo to accel while its mounted

The magnifying lens for looking at dicky contacts. Could be intermitten and yes reflow them if theres no solution. But maybe like Hadeon said the force on the connector itself, because of missing risers is the problem.
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Old 03 October 2018, 01:08   #6
reflex
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Quote:
Originally Posted by Hedeon View Post
Using risers which you can screw tight instead of the plastic ones?

I had something similar and even the weight of the SCSI cable would sometimes just dislodge the CSPPC to the point I got a black screen. Reseating would help everytime. Now the board is screwed in place.
I already have screw metallic spacers, don't use the plastic ones anymore.

Problem remain the same.
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Old 03 October 2018, 01:10   #7
reflex
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Quote:
Originally Posted by elenachen View Post
Hmm, could be the Slot or a cold solder joint. Try inspecting the backside of the connector with a magnifying lens. Is you PSU ok?
I changed 2 or 3 PSU with no result.
What should I see with the magnifying lens?
I mean what kind of problem should I see?
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Old 03 October 2018, 02:10   #8
nexus
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you wont see anything only people who do this for a living would inspect afterwards that way
you need to do as i said use a multimeter and check continuity on each pin from mobo to accel card while mounted if each pin checks out then that isnt your issue
once you done that then we can proceed further
pics would also help

Last edited by nexus; 03 October 2018 at 02:16.
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Old 03 October 2018, 05:17   #9
grelbfarlk
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The other thing I would wonder if it isn't your Mikchronic busboard working its way out. Plugging in those fullsize busboards is finicky and when you take the system apart to reseat the CPU card, you might be slightly shifting the busboard and fixing it. Unless the Accelerator is obviously coming out of the slot, next time take the side off of your tower and give the busboard a slight push along the connector, and leave the accelerator alone.

I'm just wondering if when you take your Amiga apart to reseat the accelerator you're not reseating something else which is actually fixing the issue.

How often does this happen?
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Old 03 October 2018, 10:19   #10
reflex
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Quote:
Originally Posted by grelbfarlk View Post
The other thing I would wonder if it isn't your Mikchronic busboard working its way out. Plugging in those fullsize busboards is finicky and when you take the system apart to reseat the CPU card, you might be slightly shifting the busboard and fixing it. Unless the Accelerator is obviously coming out of the slot, next time take the side off of your tower and give the busboard a slight push along the connector, and leave the accelerator alone.

I'm just wondering if when you take your Amiga apart to reseat the accelerator you're not reseating something else which is actually fixing the issue.

How often does this happen?
it'a Mediator busboard, not the original micronik one. I almost don't move the Amiga 4000 when i reseat the CPU card, it's a lot of time that i leave it open and unmount the floppy drive bay in order to access the CPU slot easily so definitely it's not the bustard the problem.

before asking here I made a lot of tests.

I have a multimeter, I can check continuity, it will be only tricky to unmount everything :P
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Old 03 October 2018, 14:08   #11
hooverphonique
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Using a multimeter to check bad solderjoints can be problematic because when pressing the probe against the joint you may affect continuity.
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Old 03 October 2018, 20:33   #12
nexus
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no you shouldnt be using that much pressure
lightly touch dont stab
its not rocket science you just take the board out with the accel mounted like he has it screwed down as he isnt using the plastic standoffs

put 1 test lead on the bottom 1 on the top check each pin simple

also like i said if his repair guy redid the socket then its possible flux made its way to the contacts from a poor cleaning job or a bad joint
still be nice to see some close up pics of this board
just fyi solder joints should be shinny not dull
and many use crappy solder
use too much creating blobs or not using enough flux
even some companies cheap out and not use enough solder

Last edited by nexus; 03 October 2018 at 20:45.
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