Burnt out track on my A1200

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Ed.D

Ed.D

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Tonight I took apart my tower so I can do some more modding to the case and noticed a burnt track on the under side of the motherboard.

I'm assuming I should be ok to repair it with a small link wire, yes?


track.jpg



track2.jpg
 
This is quite a common track burnout due to over current.
Remove the old tracking completely and solder an insulated wire of average guage between the soldered pins.

Dont use too thin a guage of wire.

TC :cool:
 
It seems I've messed up :(. Did the repair, turned it on, heard a slight pop and all I get now is a flashing power LED. Flashes 11 times, the 11th is slightly longer. I have a green screen as well.

I think I know what I did wrong. I bridged the track across to the pad marked in the following photo. Was this incorrect? ...and have I blown up my Chip RAM?

track3.jpg
 
That definitely looks like the wrong solder point, you confused the lettering labelling one of the SMD caps, with a track.
I'd have to dig out a spec sheet for the board you are working on to tell what you may have shorted, where does that track lead?
 
Hi Rojaws, thanks for your help mate. I've traced the track through to I think it's pin 4 on P9A. It's a Rev B board.

EDIT: I checked with a multimeter and it's definitely the pin indicated by the arrow.

track4.jpg


---------- Post added at 00:59 ---------- Previous post was at 00:36 ----------

...and on the front side of the board the track links as follows: That's the second pin down on the right hand side of the chip.

track5.jpg
 
Made some great progress on this one today. I've installed a socket for the ALICE chip and popped in a known working ALICE. I now have signs of life i.e. a green screen. This is because I have removed the chip RAM IC's.


Question for the techies if I may;

I'd like to add the chip RAM back in, one chip at a time. Can I do this and boot with a minimum of 512k (one chip) and would I need to add any kind of terminating link into the empty RAM positions as I go?

Thanks,
Ed.
 
Well, I thought I was getting somewhere, soldered all the chip RAM back on but I'm still getting a green screen. I did try with just one chip to start with; ...same result. :(
 
Hi,

i recently had a green screen on my 1200 mobo 2b. This was caused by one or two damaged tracks in the vicinity of the system 3.1 roms. Once these traces were repaired the purple wb prompt returned.

I would take another look at all your traces, especially in the area where you've needed to conduct repairs - is the repair complete and are there any other traces damaged near the repairs?

From what i gather a green screen may not necessarily indicate chip ram even though much of the info out there often points to chip ram...

If you've already followed the above and the green screen persists then it seems you may have a system failure due to component failure but finding the chip at fault may take some time :coffee:

Sorry i couldn't help any further
 
@Snoozy,

Thanks mate, yeah I did cause some damage to the tracks under the chip RAM but I believe I've repaired the linkage with some wire. I think some other component may have suffered. I'm hoping somebody might be able to suggest where to start looking, perhaps checking vcc, vbb? voltages at various places.

BTW I have to thank you for the thread you shared about your broken traces under the ROM socket. I won a spare broken 2B board on feebay and it had exactly the issue you had. A quick fix and working great. I'd still love to get my 1B working though as I've had it from new in the 90's and is part of my tower project.

Happy New Year! :D
 
I'd be tracing from the point where you accidentally soldered a connection looking (and smelling) for damaged components...
 
@ptp170

Thanks my friend. I'm all sniffed out looking for burnt bits :D. I think it's probably just one of the tiny smd resisitors, transistors or caps. I have the schematics, it's a shame they don't include expected voltages or signals at various regions, (might be a future project to map those :cool: ).

All the best.
 
I now have a picture but it's slightly corrupt. Had to replace ALICE and BUDGIE.

The picture below shows PAL HiRes with some odd vertical lines. My mouse pointer is diplayed twice and it has a small line added to it. The mouse will also only move vetically about 1 fifth of the screen, horizontal is ok.

I can get into a SHELL and the 'avail' command tells me I have 2Mb chip RAM.

Any ideas about what to check next would be most welcome. I'm thinking about swapping the LISA chip next. I wonder if I may have blown the whole chipset :unsure:

Cheers,
Ed.

1200bad.jpg
 
This reminds me of a problem my very first A1200 (1993) had out of the box.
Vertical lines with the border's colour, spaced exactly 32 pixels apart (the pointer was ok though).
Once I booted into ECS instead of AGA, they went away. I had hypothesised that something was wrong with 32-bit wide fetches and the last bit got lost. The service guys fixed it but never told me what the problem was, heck they wouldn't even tell me if they just replaced the complete motherboard.
Just for kicks, try booting in OCS/ECS mode.
 
:lol: LOL, just for kicks I tried, but my mouse won't move far enough on screen to select the option.
 
Try the Amiga button and arrow keys if you can't get your mouse to move. Alt is then the mouse button click. ;)
 
Ed.D said:
:lol: LOL, just for kicks I tried, but my mouse won't move far enough on screen to select the option.
Click to expand...

Are you sure the "hot spot" is in the same place as the pointer itself? My suspicion is that the pointer's being drawn in the wrong place and that you'd be able to click on the buttons if you can manage to find the right spot "blind"...
 
Thanks for the responses guys. A couple of hours and a large bag of twiglets later, I managed to fix the display by swapping out the LISA chip.

There is a remaining issue though. It takes a while to start up. I believe the Gayle chip may also have blown as I get a constant HDD LED when I add in my Fast ATA IDE interface. With just the device connected (no HDD) it boots. With a HDD connected it stops during the boot and won't go any further.

I need to test the onboard native ide first to see if a disk drive is seen in early boot up. This will hopefully tell me if Gayle needs replacing.
 
Nice stuff :thumbsup:
So the body count so far is Alice, Budgie, Lisa, possibly Gayle - think Paula's gonna make it? (booting from floppy is a good sign).
Total respect for you perseverance!
 
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