Pet Rescue
Experienced Member
Hi All it's been a while, I decided to dust off my 2001 Chicklet and have a go at repairing it.
The story so far has been a toughie!! I have repaired it, it runs for a while then fails. I repair it again and something else fails.
I don't think it likes being switched on, anyway my first lot of repairs involved the dreaded Mos 6550 Rams. A few failed and I shuffled them around and then half an hour later another failed etc.I bought two old 2114 replacement Ram boards and these worked a treat. Sure enough though on about 20 mins and it fails, this time it was the 74ls244's that had gone faulty. I replaced those two and it worked again so I left it on around 30 mins and it failed.I made an adapter to test the 6540 Roms and found one faulty. I built an adapter to use a 2716 but it didn't alter so it must have another fault as well. In my wisdom I decided to make extension wires so that I can take the mainboard out and run it outside the case for better fault finding. (bad idea!)
Unfortunately I mixed two of the wires up on the main plug J8, the one with two reds two browns and a black (got a red and brown the wrong way around). I turned on the pet and instantly blew the 0.75 A fuse. seeing what I had done wrong I put the wires back correctly. Replaced the fuse and turned it on again but Pop! it went again, from the initial fault I created upon checking the board, it had blown the middle Diode of the three in a row near J8. I replaced the damaged diode but when it turned on the transformer hums and the tube at the neck glows but nothing is on the screen. I got out my scope and checked at the Video plug J7 for the Hor, ver and vid signals and they looked fine compared to the sheet on zimmers.
So I made a composite out adapter and put that on to J7 and although it wasn't very stable it had a picture of garbage displayed on my TV.
Therefore the monitor itself no longer displays anything! Could the short have damaged the video board?
I tested the transformer and have 15VAC there and 12VDC on the voltage reg on the video board and that's as far as I have got.
It's hard enough repairing them as it is, without adding more faults myself!
Have you guys any pointers where to test on the video board or what I may have blown from my error?
The story so far has been a toughie!! I have repaired it, it runs for a while then fails. I repair it again and something else fails.
I don't think it likes being switched on, anyway my first lot of repairs involved the dreaded Mos 6550 Rams. A few failed and I shuffled them around and then half an hour later another failed etc.I bought two old 2114 replacement Ram boards and these worked a treat. Sure enough though on about 20 mins and it fails, this time it was the 74ls244's that had gone faulty. I replaced those two and it worked again so I left it on around 30 mins and it failed.I made an adapter to test the 6540 Roms and found one faulty. I built an adapter to use a 2716 but it didn't alter so it must have another fault as well. In my wisdom I decided to make extension wires so that I can take the mainboard out and run it outside the case for better fault finding. (bad idea!)
Unfortunately I mixed two of the wires up on the main plug J8, the one with two reds two browns and a black (got a red and brown the wrong way around). I turned on the pet and instantly blew the 0.75 A fuse. seeing what I had done wrong I put the wires back correctly. Replaced the fuse and turned it on again but Pop! it went again, from the initial fault I created upon checking the board, it had blown the middle Diode of the three in a row near J8. I replaced the damaged diode but when it turned on the transformer hums and the tube at the neck glows but nothing is on the screen. I got out my scope and checked at the Video plug J7 for the Hor, ver and vid signals and they looked fine compared to the sheet on zimmers.
So I made a composite out adapter and put that on to J7 and although it wasn't very stable it had a picture of garbage displayed on my TV.
Therefore the monitor itself no longer displays anything! Could the short have damaged the video board?
I tested the transformer and have 15VAC there and 12VDC on the voltage reg on the video board and that's as far as I have got.
It's hard enough repairing them as it is, without adding more faults myself!
Have you guys any pointers where to test on the video board or what I may have blown from my error?
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