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

Problems with your machine in general.
PaulJ_2.0
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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 1100 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
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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
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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
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PaulJ_2.0
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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
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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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8 Bit Dreams
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Re: A500+ Help me Obi Wan, you're my only hope.

Post by 8 Bit Dreams » Sat Jul 06, 2019 10:08 pm

Oh! great! Can You please help me!? Have similar problem here...just a small battery leakage...
2019-07-06 15.57.30.jpg
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PaulJ_2.0
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Re: A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Sat Jul 06, 2019 10:41 pm

I have fixed a whole bunch of 500+ as they are my favourite board an easy route to 2MB chipram and ECS chipset makes them the premium 500 by a long walk.

Anyhow, the first and most important thing you can do is to neutralise that alkaline with some acid. Anything will do, I'm no snob. I've used lemonade in the past, but white vinegar is preferable.

Once youre sure its done and there is no fizzing, its time to get that acid cleaned. IPA will work just fine.

Once that is done, you need to remove some of the chips and probably the Gary socket as that tends to corrode away a leg or three.
Chips you'll want to remove are U9 to U13, those have traces underneath that will need cleaning up and checking for continuity.
It's also a good idea to socket those whilst they are out, but wait until after youve done the repairs because there could be a bunch.

Use this site, it will save your sanity:
http://www.amigapcb.org/

Start at the gary chip and test all pins that the traces go to where they should, then down through U9 to U13.
dont worry too much about the passives at this point you'll be checking them with over as you're checking the traces of the chips.

Once you have done that, power it up and tell me what you do/dont see on the screen.
Oh and in the meantime, get a diagrom handy.

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

Post by 8 Bit Dreams » Sun Jul 07, 2019 12:42 am

Are You serious, Paul? I was just kidding... will NEVER EVER repair something useless like A500... its a waste of parts, to be fair...
Will Better move these parts to something like this:
20190704_194436.jpg
20190704_194436.jpg (353.91 KiB) Viewed 619 times

PaulJ_2.0
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Re: A500+ Help me Obi Wan, you're my only hope.

Post by PaulJ_2.0 » Sun Jul 07, 2019 12:51 am

Oh I was never going to get that joke, I repair those battery damaged boards on a weekly basis (I was even doing one at the time you posted the board).

Can I get that 500+ board off you when you've scavenged the parts from it?
Please dont throw it away, It hurts me when I hear people do this...

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