A500+ Help me Obi Wan, you're my only hope.

Problems with your machine in general.
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PaulJ_2.0
Posts: 48
Joined: Sat May 11, 2019 11:32 pm

A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Mon May 20, 2019 10:39 pm

New here, so if anyone has read my welcome message, you might have read that I have a couple of 500+ boards that have been the bane of my life for far too long.
I had pretty much given up on them, but I dug one out today, to see if I can find the problem (there could be multiple).
The history of it is that it had battery damage and had caused corrosion and killed Gary, the U12 IC and had taken some traces with it.
The socketed chips are all tested fine and work in another board, the ram is also all tested fine.
+12V -12V and 5V rails all test fine
I've repaired/replaced those but cant seem to get past the issue it presents now.
The light on the keyboard flashes 10 times, and I can press the caps lock 6 times (indicating the cpu isn't functioning, I think) and I have this on the screen:
IMG_20190520_222618.jpg
IMG_20190520_222618.jpg (47.44 KiB) Viewed 387 times
Does anyone have experience in what causes this? My first thought was Agnus, but that checks out and the board does the same with another inserted.
No rush, this board has been causing me headaches for an age.

Maximilian
Posts: 73
Joined: Thu Feb 28, 2019 5:02 pm

Re: A500+ Help me Obi Wan, you're my only hope.

Post by Maximilian » Wed May 22, 2019 12:05 am

For the blink codes look at:
http://www.lemonamiga.com/forum/viewtopic.php?t=13978

The first thing i would do is use http://www.amigapcb.org/ to check the traces for breaks and shorts, also check under IC's when in doubt.
If you have the correct PLCC puller i would also reseat Agnus after cleaning the socket.

What kind of Kickstart is mounted?

What does the startup look like?

PaulJ_2.0
Posts: 48
Joined: Sat May 11, 2019 11:32 pm

Re: A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Wed May 22, 2019 12:37 am

The blinks point to Agnus, but the chip is tested working as I mentioned. The socket is clean and the chip seems to be seating nicely.
Kickstart mounted makes no difference, I have put multiple in with the same result.
The screen pictured is what comes on instantly and reset loops along with the led blinks.
The goto fixes on this board aren't making any difference at all. It's almost certainly a passive or two somewhere.

terriblefire
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Re: A500+ Help me Obi Wan, you're my only hope.

Post by terriblefire » Wed May 22, 2019 7:52 am

Honestly I’d get one of the red A500+ bare boards and solder it up... battery damaged A500s are never reliable
———
I get cranky when asked to repeat myself.

PaulJ_2.0
Posts: 48
Joined: Sat May 11, 2019 11:32 pm

Re: A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Thu May 23, 2019 10:38 am

Whilst I would agree if it meant anything to me, It's just that the board is something that I would like to fix so as to increase my knowledge of such things. Renewing the board would be admitting defeat :)

PaulJ_2.0
Posts: 48
Joined: Sat May 11, 2019 11:32 pm

Re: A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Fri May 31, 2019 11:51 am

Well I decided yesterday that this particular 500+ board has been a problem for far too long and so I decided to work out what was wrong once and for all. I had previously checked all of the traces and everything checked out fine after 2 small repairs, the socketed chips all checked out fine in another board, so I knew they were all fine and I had socketed most of the other ic's and ram, all of which are known good.

So, I still had this error that pointed to Agnus and diagrom pretty much says the same as the graphical tests were falling over.
Like I said previously, the Agnus is fine as I had put it into another board and everything checked out good and if I placed another known good Agnus in the faulty board, the same error persisted.
Cant be Agnus.
All the rest of the system checked out fine with voltages and signals, so that was me stumped for ages.
Yesterday I had the idea of checking the continuity of the pins from the agnus socket, down to the underside of the board and well damn, a pin had indeed corroded on the underside of the socket. Changed the socket, reseated Angus and it fired up perfectly!

You dont want to know how many hours I have invested in this board, but the important thing is that I have learned another valuable lesson in my quest for knowledge.

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