tommywiz Posted July 2, 2021 Share Posted July 2, 2021 (edited) I can find many articles and videos about the screen on the sx64 being "blank". But these all wind up being white, blue, multii colored, scrambled characters, etc but the screen at least comes on. Many of these appear to be fixed by replacing the PLA chip. In my case the built in crt doesnt appear to come on at all! Ive turned it on in a totally dark room and dont see any "glow" coming from the crt. Ive turned all the knobs behind the little door and didnt get any change. When I turn it on I do get the brief red light on the floppy drive. Ive connected an external 1701 monitor to the video port and do not get a signal on it either. Any suggestions on where to start? Edited July 2, 2021 by tommywiz Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 3, 2021 Share Posted July 3, 2021 You could have multiple problems. I would start by checking your power supply voltages. I have a lot of spares for the SX64 if it turns out you need a replacement screen. Quote Link to comment Share on other sites More sharing options...
Papalapa Posted July 3, 2021 Share Posted July 3, 2021 (edited) Maybe do you want to replace the original TRC by an LCD display. This guy has done this job and it's explained in this forum (in Spanish) http://www.retrowiki.es/viewtopic.php?f=48&t=200037073 Edited July 3, 2021 by Papalapa Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 7, 2021 Author Share Posted July 7, 2021 An update. Thanks for all your suggestions. I tried a power supply from a know working sx 64 and got the same results. Also, how common is it to have a bad monitor on one of these? An external monitor does work if a cartridge is plugged in! Im thinking I didnt push the plug in all on way on the back of the SX. Nothing shows up on the built in or external monitor if I just turn it on or from a floppy. The only time I get video is with a cartridge in the SX out to the external monitor! An interesting issue. The wires/cable that runs from the floppy drive to the floppy controller card has come issue, it could also be the controller card. The issue is that I have to "mess with it" to get the red light on the drive or an image on the external monitor. I cannot tell if its one or more of the wires, the solder joints on the floppy drive, the connector on the controller card, or the controller card. I just have to move the wires/cable somewhere along their length on either ends to get the floppy light and external video. Visual inspection with a bright light and magnifying glass doesnt reveal any nicks, cuts, or bad solder joints on the wires/cables, connector, or floppy controller card. I realize these things could actual be there it just wasn't noticeable. BTW, Ive also replaced the PLA chip. Quote Link to comment Share on other sites More sharing options...
carlsson Posted July 7, 2021 Share Posted July 7, 2021 (edited) The fact that it boots to external monitor if you have an autostarting cartridge, and you already replaced the PLA chip, makes me wonder if you're having a faulty BASIC ROM chip. The boot routine starts at the Kernel ROM, then checks for a cartridge and if there isn't one, goes ahead to BASIC start. (or perhaps bad RAM, in case the routine that clears/checks RAM gets stuck while booting into BASIC, but I would expect the external monitor to come on with the intended background and border colours if that was the case) The monitor issue however would be a separate one, since you don't get any action from it by any means. Edited July 7, 2021 by carlsson Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 8, 2021 Share Posted July 8, 2021 7 hours ago, tommywiz said: Also, how common is it to have a bad monitor on one of these? Not common, but it happens. Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 11, 2021 Author Share Posted July 11, 2021 This machine just got a bit more weird! I haven't done anything since last time other than power cycle! Now it boots to the main blue/white READY SX-64 screen but no prompt. It will no longer boot from a cartridge! Still no love to the internal screen! Quote Link to comment Share on other sites More sharing options...
carlsson Posted July 12, 2021 Share Posted July 12, 2021 If it wasn't for the fact that you mentioned you already had replaced the PLA chip, that had been my first suspect. Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 12, 2021 Share Posted July 12, 2021 5 hours ago, carlsson said: If it wasn't for the fact that you mentioned you already had replaced the PLA chip, that had been my first suspect. It’s possible the replacement PLA is bad? @tommywiz do you have a working C64 unit you can test chips in? Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 14, 2021 Author Share Posted July 14, 2021 On 7/12/2021 at 8:11 AM, mdivancic said: It’s possible the replacement PLA is bad? @tommywiz do you have a working C64 unit you can test chips in? I have been trying to acquire one off ebay but keep getting outbid or forget to bid! ? Quote Link to comment Share on other sites More sharing options...
carlsson Posted July 14, 2021 Share Posted July 14, 2021 Hm, do you need a special PLA solution for a SX-64, so all those replacements intended for long board C64 would not work? I think there are plenty of options but perhaps not so many selling through eBay, Etsy or similar. Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 15, 2021 Share Posted July 15, 2021 Standard PLA 906114-01. Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 25, 2021 Author Share Posted July 25, 2021 Finally acquired a new PLA and C-64. Turns out the PLA that was already in the SX64 was good!!! I swapped it out for the one in the 64 and it worked! Inserted the PLA from the 64 into the SX and got the same results as before. I again removed, cleaned, and reinserted ALL socketed chips (except any that might be on the CRT boards) and can now consistently get video to an external monitor, still nothing on the internal CRT. The brown and white(?) wires/connector that run from the power supply to the CRT board shows about 12.3 volts. This is on the side that plugs into the CRT. Ive also removed the speaker so I can see the neck of the CRT and I dont see any glow when powered on. At this point Im thinking the CRT or one of its boards is where the problem lies. Ive looked at articles on replacing the CRT with an LCD but cant seem to find an LCD and controller. 1 Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 26, 2021 Share Posted July 26, 2021 I got mine here: SX64 Screen Replacement You just have to put your name on the list and wait for them to become available. Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 28, 2021 Author Share Posted July 28, 2021 On 7/26/2021 at 9:19 AM, mdivancic said: I got mine here: SX64 Screen Replacement You just have to put your name on the list and wait for them to become available. Yeah, Ive done that already. Anyone know if these come back very often? Quote Link to comment Share on other sites More sharing options...
mdivancic Posted July 28, 2021 Share Posted July 28, 2021 7 hours ago, tommywiz said: Yeah, Ive done that already. Anyone know if these come back very often? When I put mine in it was four or five months. They had five in and it took several months to sell them all. This was September of last year. I wish I had gotten two. Quote Link to comment Share on other sites More sharing options...
tommywiz Posted July 28, 2021 Author Share Posted July 28, 2021 (edited) I gather the problem is not the monitor itself but finding the right controller that has s-video enabled. Edited July 28, 2021 by tommywiz Quote Link to comment Share on other sites More sharing options...
carlsson Posted July 28, 2021 Share Posted July 28, 2021 (edited) Did you get the service manual yet? http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/sx-64/index.html Ray Carlsen also has a few things to say about the SX-64. http://personalpages.tds.net/~rcarlsen/cbm/sx64/ Edited July 28, 2021 by carlsson Quote Link to comment Share on other sites More sharing options...
tommywiz Posted August 2, 2021 Author Share Posted August 2, 2021 On 7/28/2021 at 5:43 PM, carlsson said: Did you get the service manual yet? http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/sx-64/index.html Ray Carlsen also has a few things to say about the SX-64. http://personalpages.tds.net/~rcarlsen/cbm/sx64/ Yes, Ive printed all those documents and read over them several times. Quote Link to comment Share on other sites More sharing options...
tommywiz Posted August 5, 2021 Author Share Posted August 5, 2021 OK, I just couldnt resist. Ive purchased a second SX-64. This one didnt come with the handle or keyboard and is all scratched up but it works! Well, sorta. The screen works great on this one but its all black and white, no color even on an eternal monitor. I know its not the PLA chip as Ive switched it on my other C64's and they all show color. Ive read that on a regular C-64 something called a Trimmer CT1 is at fault. Quote Link to comment Share on other sites More sharing options...
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