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Old 22 May 2013, 22:24   #1
Jawd
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Amiga 4000 repair question

As i am trying to get the A4000D working again i have some questions.
The board was working fine before i bought it (seen it working), but when i got it there was no more life in it.
After checking the board i noticed the board had the jumpers on J100 wrong, this is that it was bridged from ext to int on the middle pins and on the left pins.

. . . instead of ._. .
| | instead of ._. .
' ' '

Now i have put the jumpers good but it keeps rebooting (flickering power led).
If i have a 3630 in it and remove the chipram i get a green screen, but it keeps rebooting.
If i use a cs mk1 060 i get the rainbow colors so i guess the cpu is connected alright.
Also if i connect a deneb i get the A1000 bootsound that is active on it, getting me to think the zorro's are also good.
Looking at these two things video and sound also seem to work.
There has been some damage from a leaking battery but there seem no traces broken, there is some corrosion on the philips chips.
Before i strip half the board i thought i might ask for some tips in faultfinding.
I do have access to a good multimeter and a analogue scope...

Thanks for looking....
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Old 23 May 2013, 02:06   #2
direktorn
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Your amiga wont break down if you placed the jumpers incorrectly. Are you sure they are in the righ place? Checking your RAM is also a good practice.
How do you connect video?
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Old 23 May 2013, 02:15   #3
Jawd
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The jumpers are in the right configuration now.
The memory is known working (only chipmem present) as i pulled it from my other 4000.
All the jumpers on both boards are the same, so there should not be an error.
I use a C= 1960 monitor with the c= vga adapter.
I suspect the jumpering because the board was working before, only thing changed was those jumpers.
Those where removed because there was a 060 before and i got a 030 with the setup.
But instead of setting the jumper to internal he bridged the 2 lines, wont that make a short in the ep8700?
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Old 23 May 2013, 09:27   #4
Marcelv
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Maybe you can check the clock signals on J100 and J104 using your scope.

Or try with a 3640, if that works there is something wrong with the onboard cpu clock circuit.

Last edited by Marcelv; 23 May 2013 at 10:33.
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Old 23 May 2013, 16:24   #5
Cymru
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Amiga 4000 repair question

Or the lye from the battery leak was never washed away and is continuing to dissolve your tracks. Clock traces then ram traces then video traces.
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Old 24 May 2013, 00:55   #6
Jawd
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With a 3640 and with a cs mk1 060 i get the same results, but i will check the clock signals tomorrow. Just got home from a long day at work.
The acid from the battery should all be gone, but if the problem is not with the clock signal i think i have to strip the area around the battery and clean and check the traces beneath the chips.
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Old 24 May 2013, 02:02   #7
Marcelv
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With the 3640 and the j100 and j104 jumpers on EXT the clock on the 3640 is used...
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Old 28 May 2013, 05:31   #8
Jawd
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Been probing the clock (both internal and external) and this seems fine.
Also removed the motorolla and the two phillips chips next to where the battery once was to check and clean and also there no problems.
So re-placed those chips and as suspected (as nothing changed except some solder) changed.
I think at least, now if i put in my cs 060 or 040 without any fast memory on the 4000 board or on the cs the power-led does not flicker.
Still no action but cant remember if it did flicker before, probably not...
With a standard C= 030 or 040 led still flickers.
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Old 28 May 2013, 12:14   #9
Loedown
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You should be looking at power rails and alike, the led will sit on the +5 volt rail and if it's flickering then you are more likely to have a flakey power supply or bad capacitors. The other possibility is a subtle short or component failure which is bouncing the +5 volt rail, hence the flickering.
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Old 02 June 2013, 03:56   #10
Jawd
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It took some time but finally got around to check the volt rail at some random places and get a nice 4,97v so this seems fine, 12v line gives 11,73 a bit low but should be fine (i think???).
The psu works fine with my other 4000 so i dont think there are any problems with that.
I will explain the flickering power-led, it blinks 6 short times and than 1 long, and this repeats itself into infinity...
Replaced the buster with a know good one just to be safe but this also did not solve (or improved) anything.
So i know works:
Video (get green screen w/o chipmem and rainbow colors with CS 060)
sound (deneb with a1000 startup-tune active)
Zorro (else deneb should not work)
Keyboard (can press caps-lock 6 times until lockup, ctrl-a-a reboots)
It is getting late and i am out of ideas for the moment so will pick this up tomorrow...
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Old 02 June 2013, 09:06   #11
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Now you mention the power light in a sequence. I can't find mention on the net anywhere about POST codes that are for A4000D, it's all about screen colours usually. In having said that it may be that your CPU cards are doing the actual error reporting via the power led. Anyone else know of CPU cards that did this?

The PSU voltages are ok, within spec.
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Old 29 June 2013, 07:55   #12
EdgarZimmerma
 
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Quote:
Originally Posted by Jawd View Post
As i am trying to get the A4000D working again i have some questions.
The board was working fine before i bought it (seen it working), but when i got it there was no more life in it.
After checking the board i noticed the board had the jumpers on J100 wrong, this is that it was bridged from ext to int on the middle pins and on the left pins.

. . . instead of ._. .
| | instead of ._. .
' ' '

Now i have put the jumpers good but it keeps rebooting (flickering power
led light).
If i have a 3630 in it and remove the chipram i get a green screen, but it keeps rebooting.
If i use a cs mk1 060 i get the rainbow colors so i guess the cpu is connected alright.
Also if i connect a deneb i get the A1000 bootsound that is active on it, getting me to think the zorro's are also good.
Looking at these two things video and sound also seem to work.
There has been some damage from a leaking battery but there seem no traces broken, there is some corrosion on the philips chips.
Before i strip half the board i thought i might ask for some tips in faultfinding.
I do have access to a good multimeter and a analogue scope...

Thanks for looking...
.
Nice build up.. I am in process of getting my A4000D in working condition and I hope the thread provides me enough information...

Last edited by EdgarZimmerma; 29 June 2013 at 09:59.
 
Old 29 June 2013, 22:39   #13
Cymru
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Quote:
Originally Posted by Jawd View Post
It took some time but finally got around to check the volt rail at some random places and get a nice 4,97v so this seems fine, 12v line gives 11,73 a bit low but should be fine (i think???).
The psu works fine with my other 4000 so i dont think there are any problems with that.
I will explain the flickering power-led, it blinks 6 short times and than 1 long, and this repeats itself into infinity...
Replaced the buster with a know good one just to be safe but this also did not solve (or improved) anything.
So i know works:
Video (get green screen w/o chipmem and rainbow colors with CS 060)
sound (deneb with a1000 startup-tune active)
Zorro (else deneb should not work)
Keyboard (can press caps-lock 6 times until lockup, ctrl-a-a reboots)
It is getting late and i am out of ideas for the moment so will pick this up tomorrow...
CPU or CIA error from the caps light link. CS060 should be set to int, ROM speed to 200ns if stock ROMs, try no RAM on CS MK 1; check jumpers on Chip ram.
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Old 19 September 2013, 18:30   #14
Jawd
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Okey, it has been some time and trere is a little progress.
I got some Logica Diagnostic rom's in it to see what that would bring me...
And the damn system boots with the diag rom's and passes all tests (i only have the rom's so can't test the ports), only thing i notice i that it tells me there is no clock.
There is no battery present on this board but that also is missing from my other 4000's and on those it does not tell me there is no clock, it just shows the time (it is jumping around but there is a clock).
So my first guess would be that there is a problem with the clock circuit, does this seem reasenable to anybody else?
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Old 19 September 2013, 19:29   #15
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Well First I would say I am no expert on electronics, so here is my small idea.

Just an idea, but what ROMs do you use original 3.0 or 3.1 can you enter early startup and boot with no startup-sequence if you press both mouse buttons?

I have try older ROMs om A4000 which keeps rebooting if system has been installed with OS3.5+ or higher since it needs kickstart 40 or ROM3.1s, and I think that flashes alot on the power led no matter what CPU card you use and it keeps rebooting like and endless loop, unless you boot without a startup-sequence.

Is it possible for you to try with ROM3.1 on your system or is it just ROM3.0? (just an idea)
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Old 19 September 2013, 20:12   #16
Jawd
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I tried 3.0 and 3.1 roms... same result, dark screen and blinking powerled and reboots almost directly after poweron.
So it wont get to early startup
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Old 19 September 2013, 21:04   #17
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did you try to reseat all chips?
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Old 19 September 2013, 21:08   #18
Jawd
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Jep, all chips are well seated, also everything (sound, video, zorro, chip-ram, diskdrive) seems to work.
Only when a normal kickstart is used it refuses to boot-up....
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Old 20 September 2013, 07:28   #19
Loedown
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Quote:
Originally Posted by Jawd View Post
Okey, it has been some time and trere is a little progress.
I got some Logica Diagnostic rom's in it to see what that would bring me...
And the damn system boots with the diag rom's and passes all tests (i only have the rom's so can't test the ports), only thing i notice i that it tells me there is no clock.
There is no battery present on this board but that also is missing from my other 4000's and on those it does not tell me there is no clock, it just shows the time (it is jumping around but there is a clock).
So my first guess would be that there is a problem with the clock circuit, does this seem reasenable to anybody else?
No I think there's an address error or switching error, check your logic circuitry and I would bet the clock is mapped high in the address lines, something isn't switching properly. From what I recall the diagnostic ROM is smaller than Kickstart and you may not be accessing the faulty address line is my theory without looking at the schematics.

Now I've looked at the schematic, check U177 and make sure that RP176 is orientated the correct way. The whole fault is connected between booting and not seeing the clock, also check that the battery isn't flat.

Last edited by Loedown; 20 September 2013 at 07:49.
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Old 29 September 2013, 20:53   #20
Jawd
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@Loedown: Thanks for the response, you might be right about the diag-rom.
It is indeed smaller than a normal rom.
I already replaced U177 last time (in the right orientation) but I have some ordered and will try replacing it again as it might be possible this one was bad also.
The battery is missing so i guess that means flat; but should the clock not work anyway, it just would not save the time...right?
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