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Old 03 May 2020, 14:14   #1
Alien8
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Did I kill my A4000D motherboard?

After many years out of the Amiga scene I finally got the time (confinement at home) to mess with my two Amigas again.

The A500 was in pretty good shape, so I replaced the FDD with a Gotek and the HDD in the GVP Impact II with a SCSI2SD interface. It was great fun getting both working. Next I wanted to upgrade the 1.3 ROM and found the Romulator, but is out of stock. I hope they make some more and I can get one.

During this both my monitors, 1084S and 1085S, died… now I have to wait until I can get out and have them repaired, so the A500 is on hold. I did order a scart cable to connect the A500 to a TV but I’m still waiting for it to arrive.

Turned my attention to the A4000D. I let that one to last because I was afraid of what I could find… and I was right, the battery had leaked. Removed the battery and cleaned the board the best I could. The damage was not to severe but there was damage.

Checked the power supply and it is in very good condition. All caps look good and voltages are rock solid. Since the A4000D has an RTG card I connected a VGA monitor and turned it on… great is working with only some minor faults that I thought could be fixed when I get the motherboard recapped by an Amiga tech service.

Time to “modernize” some easy things, like adding a Gotek as DF0: and keeping the FDD as DF1:. Got both working very well.

Time to replace the very old HDD with a CF adapter, but needed another FDD power plug for the adapter because the power supply only has two and I used those for the Gotek and the FDD… and this where I did fuxxup big time. Being a moron I failed to notice that the +5V and +12V lines in the HDD plugs are reversed from the FDD plugs.

Now the Amiga doesn’t boot and stays in a black screen.

Did I kill my A4000D motherboard or is it repairable?
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Old 03 May 2020, 14:44   #2
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Does your Caps Lock light blink or flash on power up?
Does your power light go on?

Remember that if you are running Kickstart 3.1 it will take forever (30 secs or so) to get to boot screen.

Last edited by theq; 03 May 2020 at 14:50. Reason: Added comments
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Old 03 May 2020, 15:07   #3
Alien8
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Yes, the caps lock flashes briefly and the power led is on.

I did wait for several minutes, because with nothing in the IDE connector, the boot times are very long. Noticed that when booting from the Gotek after installing it.
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Old 03 May 2020, 16:40   #4
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CPU seems fine then. Might help to reseat the CPU card.

I suggest getting a DiagROM, otherwise you'd have to trace which signal you have or haven't from the different chips.
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Old 04 May 2020, 02:37   #5
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Does the Caps lock light respond after 5-6 presses? As in can you turn the caps lock light on 10 times in a row?

And does the Power LED go High, just turning on doesn't really tell you anything. It should turn on then go brighter when the CPU is working.

But sure reseat the CPU card.
I actually did the same thing you did at one time and the power supply crowbarred, but no actual damage was done.
Most of the pins attached to the IDE connector go to the buffers and two GALs which make up the IDE controller. Those are all common parts (not custom chips) which should be easy enough to replace. Like U901-U904 and U351-U355.
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Old 04 May 2020, 21:54   #6
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Quote:
Originally Posted by theq View Post
CPU seems fine then. Might help to reseat the CPU card.

I suggest getting a DiagROM, otherwise you'd have to trace which signal you have or haven't from the different chips.
I removed and inserted the CPU card again. No change in the booting.

I ordered a set of DiagROM's 1.2 for the A4000, but I think I'll need a monitor on the Amiga video connector. Right now I have a VGA monitor connected to the CyberVision and I think the DiagROM doesn't output through an RTG card.
I'll try to get my monitors to a repair shop tomorrow. It's not that I can try the rom's before they arrive.

Quote:
Originally Posted by grelbfarlk View Post
Does the Caps lock light respond after 5-6 presses? As in can you turn the caps lock light on 10 times in a row?

And does the Power LED go High, just turning on doesn't really tell you anything. It should turn on then go brighter when the CPU is working.

But sure reseat the CPU card.
I actually did the same thing you did at one time and the power supply crowbarred, but no actual damage was done.
Most of the pins attached to the IDE connector go to the buffers and two GALs which make up the IDE controller. Those are all common parts (not custom chips) which should be easy enough to replace. Like U901-U904 and U351-U355.
No, the caps lock doesn't work. The led flashes on power up and when I do the keyboard reset 3 key combo but nothing more.

The brightness of the power led remains constant. I can't see any changes.

If one or more of the chips you referred need replacing I'll need someone to do it for me because messing with surface mounted components is beyond my abilities.
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Old 04 May 2020, 22:21   #7
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Then it sounds like you did kill your A4000. It could be the accelerator or some component on the motherboard, hard to say.
It's sounding like you gave it a pretty significant power event, did you let the magic smoke out? The power supply could be questionable at this stage as well and if knackered enough can make the machine not boot too-not that likely but possible.
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Old 06 May 2020, 20:15   #8
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Happy

I remembered that I still have my original A3640 board that came with the Amiga.
Took out the CyberStorm and put the A3640 in... no boot, black screen. So it's not the CPU but the board itself.

Magic smoke?
Nope, didn't get any, thankfully!

I checked the power supply again and, according to my voltmeter, it's ok.

I had contacted Amigastore before to arrange for a recap. I was waiting to the restritions to be eased a bit before sending it to them. Now I hope they can fixit.
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Old 07 May 2020, 01:06   #9
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Which Cyberstorm was it, did you move the jumpers to EXT for the A3640?
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Old 07 May 2020, 09:01   #10
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i can repair your mobo
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Old 08 May 2020, 10:21   #11
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Have you disconnected everything on the IDE just leaving the floppy drive connected?
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Old 08 May 2020, 12:29   #12
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Quote:
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CPU seems fine then. Might help to reseat the CPU card.
.
One flash of the keyboard is from the controller, I think. It means you have power. When the CPU is running, you can press it more than 5 times as without CPU the buffer runs full and the caps-lock stops going on and off (this is what griblebark hints at).
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Old 08 May 2020, 17:06   #13
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Quote:
Originally Posted by grelbfarlk View Post
Which Cyberstorm was it, did you move the jumpers to EXT for the A3640?
It's an Mk II with the 060 CPU.
Regarding the jumpers, I did move them from the INT to the EXT position for the A3640 board.


Quote:
Originally Posted by cpiac64 View Post
i can repair your mobo
Really!? :-)
That would be wonderful!


Quote:
Originally Posted by theq View Post
Have you disconnected everything on the IDE just leaving the floppy drive connected?
Yes, I tried with nothing connect, with only the Gotek, with only the FDD and even with the old HDD, and got no reaction from de Amiga.
The Gotek has a small OLED display and I can see that it selects the adf file (I think it means that the drive is ready) but no reading occurs.


Quote:
Originally Posted by Hedeon View Post
One flash of the keyboard is from the controller, I think. It means you have power. When the CPU is running, you can press it more than 5 times as without CPU the buffer runs full and the caps-lock stops going on and off (this is what griblebark hints at).
So none of the CPU's is working when I power up the Amiga, or at least, the board is not listening to them.
Maybe they don't get initialized because of missing signals?
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Old 08 May 2020, 18:10   #14
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If I understand correctly you wired up a FDD but swapped the 5v & 12v lines. This should have just fried the CF adapter I think.

Have you tried removing everything? All drives, floppies and even the zorro riser.
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Old 09 May 2020, 18:23   #15
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If I understand correctly you wired up a FDD but swapped the 5v & 12v lines. This should have just fried the CF adapter I think.

Have you tried removing everything? All drives, floppies and even the zorro riser.
Yes, I did swap the 5v and 12v lines in the FDD plug that I needed to power the adapter.
I don't know about the adapter because I can't test it, but the CF card isn't damaged. I test it in a PC with a USB card reader and it is working normally.
I formatted and filled it with files and then tested the files from the card and got no errors.

I removed all the drives and tried with one at a time and with no drives, got nothing from the board.

As for the zorro riser, I didn't remove that one because I need it to connect the CyberVision card. As soon as I get my 1085S repaired, or the RGB cable I ordered arrives, I'll try with no graphic card and no riser.
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Old 09 May 2020, 21:08   #16
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Understand. Hope it works out.
I think DiagROM outputs on the serial port so you might want to get a null modem cable.
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Old 10 May 2020, 03:21   #17
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If your Power LED doesn't go from half->full bright after about 1 seconds on powerup then your system is stuck in early boot sequence. If the battery damage (corrosion) is extensive then it's pretty typical that the tracks around the RTC circuit are weakened, and often the tracks on the other side of the barrel battery also (around the corner of the SIMM sockets).

When people try to clean the battery area I've seen many times that tracks break and create opens when the PCB is scrubbed (even if gently) especially around the 3 TTLs that sit below the RTC area (U975,976 and 177) and above the battery at the larger buffer chip (U891). These sit directly on the address bus and could cause all kind of issues if they can't do their job, in your case I would bet on U891 and the are around it. But hard to tell just based on the symptoms. Btw. just recapping won't make this problem go away, no point trying.
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Old 10 May 2020, 05:34   #18
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It’s dead Jim, time for a resurrection.
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Old 18 May 2020, 19:24   #19
Alien8
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Finally I have my 1085S repaired and the DiagROM's 1.2.
Time to strip the board to the minimum and do some tests!

Now, the HI and LO ROM chips got on to which side...
HI ROM is to be used at U175 on the Amiga 4000, that's the right socket.
LO ROM is to be used at U176 on the Amiga 4000, left socket.

I'll post the results of the tests later.
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Old 22 May 2020, 16:16   #20
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First test:
A4000 motherboard with 3.1 ROMS + A3640 + 2 MB CHIP RAM + Original power supply + 1085S + Keyboard + MOUSE =
Kick blink of caps lock (but that key was not working before, one of the small faults identified before the fuxxup event); power led displays constant brightness; no reaction on the monitor display, nothing!
Powered it off after 3 minutes of waiting.

Second test:
A4000 motherboard with 3.1 ROMS + A3640 + 2 MB CHIP RAM + PC power supply with connector adapter + 1085S + Keyboard + MOUSE =
Got the same results of the first test.
After that tested the PC power supply with a voltmeter and the 12v lines are under the minimum levels.
In the next test I will use only the original power supply.

Third test:
A4000 motherboard with DiagROMS 1.2 + A3640 + 2 MB CHIP RAM + Original power supply + 1085S + Keyboard + MOUSE =
And again, nothing!
Obviously there's no video output from the motherboard.
I known the DiagRoMS output some data thought the serial port, but I have nothing to connect to it.

So it's really dead! :-(

Time to get it repaired.

Maybe I should accept cpiac64 offer or search for alternatives?
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