• Please review our updated Terms and Rules here
  • Exhibitor application for VCF West 2022 is now open! If you are interested in exhibiting, please fill out the form here.

Amiga A500 REV 5A

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9
Hey there i have a issue with a old amiga 500 that is not working right now. It has the green screen as the issue as well as the beep code for the keyboard is 10 shorts 1 long. i found it is issue with fat agnus but after confirming it is working on diffrent amiga it doesn't make sense. the ram chips were replaced and still nothing is working. all the chips have been tested. is there any idea what could be stopping it? if this helps, she was found in dumpster all soaking wet. thankfully we dried it out and seem to be without any major damage. i tested the Ram data lines and Adress line all the way from the chips to Denise and agnus.

Edit: i miss read the revison and it is actually 6A not 5A!
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
5,269
Location
Connecticut, USA
first off cut that old barrel battery off. Its ancient and dangerous. has it started leaking yet? the image quality of that picture is low and doesnt really show anything
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9
I am not certain which one do you mean. if you could circle in one that you are speakign of? also i never even noticed any spills or leaks from any of the capacitors and all of them were intact.
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9
i think i should recap the whole life time with me and all that was done with it. My father found it in the trash bin in the rain during one cold day. it didn't freeze but it was really soaked through. we send it out to debug to a electronic guy who wanted to try out to "fix" it all he did was take it apart and said ram is bad. it sat at our desk for 2 years till we found a museum that fixes vintage computers. they managed to do a lot of work for rather cheap and get few things straight. First. they replaced all the ram chips and put them on sockets as well as they cleaned all the chips up so there was connectivity. One major issue they found was a JP2 was cut. so they managed to fix that up and get it to somewhat working order. they tried to check the traces because the upper 256 KB of ram was not working alright even if they changed up the chips. it was random and predictable. they went through it with mircoscope and tried to find all the issues near the ram chips and the data path so they could fix the passthrough or trace that is faulty. i will post all the img onto imgur and describe them all. They suspect that there might be a issue with traces but what is a odd ball that after testing all the Adress traces and Data traces nothing seemed wrong.
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9

the image order is a mess but from what they explained / said they did the order of action was around

1. Diagnostics. The board does not function and there seem to be a issue with ram.
2. Detach the ram and chips
3. added the legs and sockets for ram, paul and gary
4. replaced Ram and checked if it worked. as well as cleaned up the chips.
5. still doesn't work. But found the JP2 cut and set it to 1 and 2 soldered.
6. it seem to work but isn't persisent. sometimes breaks and can't read the 256KB futher.

At this point we were informed that they suspect a broken trace but it will work 99% of time if it is left alone. We were excited to see it live. they proposed they could look through the mircoscope. they also showed up the pictures and itemized what they replaced

[ ] 4x 44256 ram replaced
[ ] 4x sockets for ram 20pin
[ ] 2 springs for keyboard
[ ] Diagnosys
[ ] Cleaning the chips
[ ] Amikit
[ ] Diagrom
[ ] 2x 48pin sockets (gary, paula)
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
5,269
Location
Connecticut, USA
I said the barrel battery, cut off the barrel battery. Its probably leaking. All amigas have this issue. You can test the system without that RTC ram board anyway, but you should cut it off. As far as recapping it. Thats up to you but I didnt say you need to do it at this point.
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
5,269
Location
Connecticut, USA
You said you found it in a dumpster all wet. I would be concerned something got on the board and could be causing a short. Im a a big advocate for washing boards in the dishwasher to ensure there is no gunk or electrolytics, etc on the board. Wash it WITHOUT a heat cycle. You can remove all the socketed chips and check the legs and clean any dirty contacts if necessary. You said you replaced the RAM and they were "checked" what does that mean?

When I got my A500 it had battery damage. I had to soak it in vinegar for 2 days to neutralize the battery leakage. Then I washed it twice in the dishwasher to get the board sparkling. My amiga came with the ramboard and battery that was destroyed by the battery so I took it out. It also had this 1MB upgrade which runs a line to clip onto the Gary chip. There is also a cut trace (deliberately) on the board. I left it that way as I got it working in its current setup. I did replace the electrolytics because of how dingy the board was when I got it.
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9
i managed to find the exact issue. i didn't replace it my self. i found a group of people who were interested in the vintage computers they did that for me since they had plenty of other amigas. it came out to be a shortage RAS0 with ground near U35 chip resulting the ram to malfunction. i literally fixed it yesterday late at night.
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9
to be exact the back side of the U35 pin 19 solder was going on a _RAS0 trace resulting in ground shortining the trace pulling it constantly low.
 

Lsmine0

New Member
Joined
Jan 23, 2022
Messages
9

the image order is a mess but from what they explained / said they did the order of action was around

1. Diagnostics. The board does not function and there seem to be a issue with ram.
2. Detach the ram and chips
3. added the legs and sockets for ram, paul and gary
4. replaced Ram and checked if it worked. as well as cleaned up the chips.
5. still doesn't work. But found the JP2 cut and set it to 1 and 2 soldered.
6. it seem to work but isn't persisent. sometimes breaks and can't read the 256KB futher.

At this point we were informed that they suspect a broken trace but it will work 99% of time if it is left alone. We were excited to see it live. they proposed they could look through the mircoscope. they also showed up the pictures and itemized what they replaced
i shared it here.
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
5,269
Location
Connecticut, USA
So in a nutshell they socketed the RAM and soldered 1 trace. I mean photos of the repair not the screen. (board pictures)
 
Top