C128 display problems
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Hi again,
OK it's for 90% the timing IC near VIC II. I ordered one but I don't if it's the right one. It's a CBM timing IC for C128 but on my C128 it have 3885 S inscription and on the ordered one 3701 (PAL / NTSC or another version of the same IC?). Anyway I concluded this when after a "toothbrushing" of the IC and socket with isopropranolol the C128 started to works correctly for 15 minutes then the same problem with display. Another wash'n'go of the IC and another 15 minutes of no display craziness.... :roll:
OK it's for 90% the timing IC near VIC II. I ordered one but I don't if it's the right one. It's a CBM timing IC for C128 but on my C128 it have 3885 S inscription and on the ordered one 3701 (PAL / NTSC or another version of the same IC?). Anyway I concluded this when after a "toothbrushing" of the IC and socket with isopropranolol the C128 started to works correctly for 15 minutes then the same problem with display. Another wash'n'go of the IC and another 15 minutes of no display craziness.... :roll:
Overheating not so sure. When switching off for 30 minutes to let the ICs to cool down and then switching on the problem still persist. Only a good washing with isopropranolol and a toothbrush of the IC and the socket makes the C128 to works proprely for a while (about 10 to 15 minutes). It may be a combined overheating and bad chip problem (while the case is open the problems occurs after 10-15 minutes, if closed after 5 to 8 minutes).
Cleaning it with isopropyl will cause a cooling action too as the alcohol evaporates and takes with it excess heat. You could probably confirm that by adding a small heatsink.
Does the chip feel warm under operation? If not, it could be possible that one of the connections is ever so slightly fractured. As the system warms up, it causes the fracture to expand slightly leading to weird errors. reflowing the sockets connections on the motherboard would sort that out, hopefully.
Does the chip feel warm under operation? If not, it could be possible that one of the connections is ever so slightly fractured. As the system warms up, it causes the fracture to expand slightly leading to weird errors. reflowing the sockets connections on the motherboard would sort that out, hopefully.
Interestingly, you mention that you are getting errors due to the timing IC. 9v is used by the CIA chip which is tied in with the ToD and connected to the PAL/ NTSC selection.
Have you tested what voltages that the VIC II and those ICs you mention are receiving?
Have you tested what voltages that the VIC II and those ICs you mention are receiving?
If i have time today I will try to add some thermal paste on the IC and a small aluminium plate and why not to measure voltage on VIC II and timming IC.
---------- Post added at 11:08 ---------- Previous post was at 10:49 ----------
Hmmm cannot find timing IC pinout.....
---------- Post added at 11:08 ---------- Previous post was at 10:49 ----------
Hmmm cannot find timing IC pinout.....
It's maybe not a too good thing but it was defective so.... Anyway I ordered the IC and I hope that my C128 and me, after the chip replacement, will live happy for.....the next failure 
I'm feeling like a romantic writer, fighting for a long lost and fogotten cause
Starting at the beginning, I started the c128 again yesterday and the same problem stiil there. I opened the c128 resoldered the socket, washed it with isopropranolol as well as the ICs' pins. I checked the connection between the upper edge of the pins and the back of the mobo (everything was OK) then some nearest tracks (OK there too). Put some thermal paste and a small heat dispatcher on the IC. Started the c128 and it worked fine for 8-10 minutes then black screen (the power led was lit though). Turned off the computer then turned on nothing the same black screen (power led on).
I'm feeling like a romantic writer, fighting for a long lost and fogotten cause
Starting at the beginning, I started the c128 again yesterday and the same problem stiil there. I opened the c128 resoldered the socket, washed it with isopropranolol as well as the ICs' pins. I checked the connection between the upper edge of the pins and the back of the mobo (everything was OK) then some nearest tracks (OK there too). Put some thermal paste and a small heat dispatcher on the IC. Started the c128 and it worked fine for 8-10 minutes then black screen (the power led was lit though). Turned off the computer then turned on nothing the same black screen (power led on).
Last edited:
Hi,
I checked the VIC II voltage and it's 4.94VDC. I took a 8701 chip from the C64C and inserted it to the c128. The C128 worked without a problem for 10 minutes then the same display error. Reinserted the chip in the c64 and everything fine.....
What is going on....:double
I checked the VIC II voltage and it's 4.94VDC. I took a 8701 chip from the C64C and inserted it to the c128. The C128 worked without a problem for 10 minutes then the same display error. Reinserted the chip in the c64 and everything fine.....
What is going on....:double
