Help! - My beautiful A500+ suddenly died

stephenfalken

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Lancashire
Hey guys. My beautiful A500+ suddenly died on me yesterday evening and I really need help getting it going again!

I have had this machine for years and removed the battery years ago, and there was a little bit of leakage but nothing too serious and I cleaned it up best I could. The machine was running and I was playing Prince of Persia when the screen suddenly went black. I didn't think too much of it and figured the game had just crashed or something. Sadly a soft reset or complete power off now just produces a blank black screen :(

There is a signal being produced, as my SCART connection activates and changes to the correct tv source etc - but there is no output at all, just a stable power LED (ie it doesn't change brightness like a usual boot), and there is no floppy seek so it doesn't look like the boot sequence is even starting.

I have done some basic troubleshooting, I have an older plain A500 machine so one by one I tested each of the socketed chips in the other A500 and everything works as expected?! (apart from Agnus, I dont want to risk bending one of those pins)

I'm really not sure what to do next. I thought perhaps there was some battery damage that I hadn't noticed before, and a few of the pins on GARY were a little green, but not by much and all the chips came out of their sockets OK, so cleaned those up.

I just can't understand why it would suddenly give up like that while being used... it had been running a couple of hours perhaps.

Below are a few photos of the board, I have followed a few of the tracks in the battery area and checked for continuity and I cant find any broken. Can anyone spot anything amiss or point me towards anything worth checking?

Im really gutted as this is my only 2MB chip A500.

Note: The 68000 in here originally came from a different machine so has a bit of green on the pins (it originally belonged in an A2000), but the CPU works fine in the other machine so am happy that isn't at fault...

HELP!! ... and thanks in advance

Edit: Just remembered that the forum resized the images, HiRes versions here:
http://8bitdreaming.com/A1000/IMG_1844.jpg
http://8bitdreaming.com/A1000/IMG_1845.jpg
http://8bitdreaming.com/A1000/IMG_1846.jpg
http://8bitdreaming.com/A1000/IMG_1846.jpg

IMG_1844.jpg


IMG_1845.jpg


IMG_1846.jpg


IMG_1847.jpg
 
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You could try another Gary or Paula from another machine? If you have one available.

Sadly I'm not much help with repairs but if you bring it along to Cheltenham there's a whole bunch of experts going to be there :)
 
You could try another Gary or Paula from another machine? If you have one available.

Sadly I'm not much help with repairs but if you bring it along to Cheltenham there's a whole bunch of experts going to be there :)

Thanks for the reply Steve. As it happens this was the machine I was planning on bringing to Cheltenham... but to use, not repair lol

I have tried Gary and Paula from this machine in another working plain A500 and they work fine so I don't suspect them at this point.
 
You won't be able to test the agnus in a standard 500 as its not pin compatible. The 500 uses the 8371/8372 1mb agnus while the 500+ uses the 8375 2mb agnus.

Personally i'd remove all chips and clean the legs and sockets with some ipa/contact cleaner ( i know you've said you've tried them in a 500 but still worth trying).
If you're getting a black screen i'd start with trying a different CPU, next i would try another kickstart rom and see if you get anywhere
 
You won't be able to test the agnus in a standard 500 as its not pin compatible. The 500 uses the 8371/8372 1mb agnus while the 500+ uses the 8375 2mb agnus.

Personally i'd remove all chips and clean the legs and sockets with some ipa/contact cleaner ( i know you've said you've tried them in a 500 but still worth trying).
If you're getting a black screen i'd start with trying a different CPU, next i would try another kickstart rom and see if you get anywhere

Yeh I know about the different Agnus, but hate removing them anyway. Good point about cleaning the legs and sockets, will give that a try - thanks.

If I recall correctly, even without a Kickstart the Amiga should still boot possibly to a coloured screen, is that right?

Many thanks :)
 
You won't be able to test the agnus in a standard 500 as its not pin compatible. The 500 uses the 8371/8372 1mb agnus while the 500+ uses the 8375 2mb agnus.

Personally i'd remove all chips and clean the legs and sockets with some ipa/contact cleaner ( i know you've said you've tried them in a 500 but still worth trying).
If you're getting a black screen i'd start with trying a different CPU, next i would try another kickstart rom and see if you get anywhere

+1

My A500+ came as not working, black screen no boot etc etc. I just cleaned and reseated all the custom ICs and it is working just fine since then. Give it a try.
 
Hey guys. My beautiful A500+ suddenly died on me yesterday evening and I really need help getting it going again!

I have had this machine for years and removed the battery years ago, and there was a little bit of leakage but nothing too serious and I cleaned it up best I could. The machine was running and I was playing Prince of Persia when the screen suddenly went black. I didn't think too much of it and figured the game had just crashed or something. Sadly a soft reset or complete power off now just produces a blank black screen :(

There is a signal being produced, as my SCART connection activates and changes to the correct tv source etc - but there is no output at all, just a stable power LED (ie it doesn't change brightness like a usual boot), and there is no floppy seek so it doesn't look like the boot sequence is even starting.

I have done some basic troubleshooting, I have an older plain A500 machine so one by one I tested each of the socketed chips in the other A500 and everything works as expected?! (apart from Agnus, I dont want to risk bending one of those pins)

I'm really not sure what to do next. I thought perhaps there was some battery damage that I hadn't noticed before, and a few of the pins on GARY were a little green, but not by much and all the chips came out of their sockets OK, so cleaned those up.

I just can't understand why it would suddenly give up like that while being used... it had been running a couple of hours perhaps.

Below are a few photos of the board, I have followed a few of the tracks in the battery area and checked for continuity and I cant find any broken. Can anyone spot anything amiss or point me towards anything worth checking?

Im really gutted as this is my only 2MB chip A500.

Note: The 68000 in here originally came from a different machine so has a bit of green on the pins (it originally belonged in an A2000), but the CPU works fine in the other machine so am happy that isn't at fault...

HELP!! ... and thanks in advance

Edit: Just remembered that the forum resized the images, HiRes versions here:
http://8bitdreaming.com/A1000/IMG_1844.jpg
http://8bitdreaming.com/A1000/IMG_1845.jpg
http://8bitdreaming.com/A1000/IMG_1846.jpg
http://8bitdreaming.com/A1000/IMG_1846.jpg

View attachment 143897


View attachment 143898


View attachment 143899


View attachment 143900

Sad to hear, but start with checking your powersupply.

Ahh, re-read and saw you are swapping parts.... so I guess power is good.

Tommy
 
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maybe even traces to left of the battery (black screen if they are cut) or gary/paula sockets... you really need to take off those buffers u12 etc to really see under the traces, plus that corrosion can travel under the soldermask unfortunately, it's why i sourced a rare a500+ sold as 500 without battery. can never trust a leak as it could be more serious over time.
 
Cheers for all the suggestions so far. I spent a couple more hours on it tonight without any luck.

I've just been probing with a meter and noticed that the RST line seems to be held permenantly low. From what I gather this should stay low momentarily after powering up then release? Maybe something is holding it low preventing the CPU from starting. I'm drawn to the 555 timer at U42... but don't have time to be desoldering right now however lol
 
Short reset with some mini-croc ? It's probably more the capacitor that the IC

Capacitor you think?

Im just curious as to why it suddenly died while in use. I would have thought a cap issue would show intermittent behaviour or perhaps fail at next power on.

Is there anything else that could fail and hold the RST low permanently?

Thanks!
 
Ok so if I remove GARY and power up the system, RST goes high a moment after power up. With gary back in, RST stays low...

This gary works fine in another A500 though so doubt that is causing the problem.
 
Cheers for all the suggestions so far. I spent a couple more hours on it tonight without any luck.

I've just been probing with a meter and noticed that the RST line seems to be held permenantly low. From what I gather this should stay low momentarily after powering up then release? Maybe something is holding it low preventing the CPU from starting. I'm drawn to the 555 timer at U42... but don't have time to be desoldering right now however lol

You can isolate 555 by cutting JP1 open. This will disable the initial power-up reset of course, you will have to manually issue a keyboard reset to the same effect after power-up. If nothing changes, you can re-bridge JP1 and look elsewhere for the problem.
 
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