Hi Reviving Retro. Thanks for all your great SX-64 videos, as there aren't too many great resources for fixing SX-64's about the place. I have a question if i can. I was recently very lucky to obtain on SX-64 in Australia. It came in great condition, worked perfectly, and even had the Commodore storage bag! Cost $1500AUD mind you, but that's life in Australia. Anyway, I started playing around with it, and about 30 mins in, I discovered that the SID, while working, sounded terrible. Swapped it out for another and bang... white screen. I've tested everything - all removable chips have been tested and all are working in multiple C64s. Tried only with the mainboard, and with the IO board to try a dead test cartridge, but still only have a white screen, no flashers or symbols like this video. I'm not new to fixing the odd Commodore machine but really don't want to stuff this one - considering how much i've paid! I have new RAM and 74LS257's available (UA3 and UB3) as Im assuming this is the next thing to look at? I'm wondering if you might have any recommendations or suggestions for next steps? Thanks in advance! Adam
I would try it without the SID chip installed. Keep it out and try the dead test cart. If still white screen I would take the main board out. You probably already know this, but you don't have to have the main board plugged in to test - just have the power and video connected to it. I would retest your chips again, especially PLA, ROMS and VIC-II. Make sure they're plugged in well and facing the correct direction. You no doubt saw the mistake I made in my video here :) If you still get a white screen and you've tested all the socketed chips then I'm afraid it starts coming down to RAM or the multiplexers, but those going out is not very typical. At this point though, you have the main board out so it's a matter of finding the bad element. Unfortunately, even an oscilloscope isn't very useful here because a bad RAM could potentially cascade its issue to others causing false readings.
great fix - the 82s100 PLAs are very reliable (not being MOS logic) - UE3 OTH like all MOS replacements ICs for normal logic would also be my fist suspicion :-)
Agreed - rare I come across a dead 82S100 - I burn my own PLAs using PLS100N chips which do the job nicely as well. Of all the SX-64 repairs I've done where the drive has had an issues, that UE3 (when it's been a 7707), has been consistently faulty :) BTW - I loved your SX-64/Kawari video. I'm working on a super modded sx-64 right now and used your video as a guide to put in NTSC/PAL switching. I hadn't thought of doing that until I saw your well put together video. If folks are reading this, they should click on your channel name here and check that video out!
@@revivingretro Thanks for the shout! I was actually so surprised it worked I just threw together the video as I went. I probably should re-do it properly, LOL.
Hi Reviving Retro.
Thanks for all your great SX-64 videos, as there aren't too many great resources for fixing SX-64's about the place.
I have a question if i can. I was recently very lucky to obtain on SX-64 in Australia. It came in great condition, worked perfectly, and even had the Commodore storage bag! Cost $1500AUD mind you, but that's life in Australia.
Anyway, I started playing around with it, and about 30 mins in, I discovered that the SID, while working, sounded terrible. Swapped it out for another and bang... white screen. I've tested everything - all removable chips have been tested and all are working in multiple C64s.
Tried only with the mainboard, and with the IO board to try a dead test cartridge, but still only have a white screen, no flashers or symbols like this video. I'm not new to fixing the odd Commodore machine but really don't want to stuff this one - considering how much i've paid!
I have new RAM and 74LS257's available (UA3 and UB3) as Im assuming this is the next thing to look at?
I'm wondering if you might have any recommendations or suggestions for next steps?
Thanks in advance!
Adam
I would try it without the SID chip installed. Keep it out and try the dead test cart. If still white screen I would take the main board out. You probably already know this, but you don't have to have the main board plugged in to test - just have the power and video connected to it. I would retest your chips again, especially PLA, ROMS and VIC-II. Make sure they're plugged in well and facing the correct direction. You no doubt saw the mistake I made in my video here :)
If you still get a white screen and you've tested all the socketed chips then I'm afraid it starts coming down to RAM or the multiplexers, but those going out is not very typical. At this point though, you have the main board out so it's a matter of finding the bad element. Unfortunately, even an oscilloscope isn't very useful here because a bad RAM could potentially cascade its issue to others causing false readings.
great fix - the 82s100 PLAs are very reliable (not being MOS logic) - UE3 OTH like all MOS replacements ICs for normal logic would also be my fist suspicion :-)
Agreed - rare I come across a dead 82S100 - I burn my own PLAs using PLS100N chips which do the job nicely as well. Of all the SX-64 repairs I've done where the drive has had an issues, that UE3 (when it's been a 7707), has been consistently faulty :)
BTW - I loved your SX-64/Kawari video. I'm working on a super modded sx-64 right now and used your video as a guide to put in NTSC/PAL switching. I hadn't thought of doing that until I saw your well put together video. If folks are reading this, they should click on your channel name here and check that video out!
@@revivingretro Thanks for the shout! I was actually so surprised it worked I just threw together the video as I went. I probably should re-do it properly, LOL.
Are you planning to sale the surplus of sx64 you have? 🙂
I only sell units locally now and then when collectors visit Grants Pass, Oregon - I don't ship for now. Sorry. Maybe one day in the future.