Paweł Posted April 20, 2022 Share Posted April 20, 2022 I'm trying to fix my old SC1224 (goldstar ca-3) monitor which was in basement around 20 years ;-). I know that it was faulty when it was stored. Root cause was as kid I broke V.Lin adjustable resistor (R635) and it was replaced by someone who at that time had TV repair shop ;-), but still not working. I run it and it was looks like that V deflection is not working (big white line on the screen). I figured out that V.Size adjustable resistor (R616) had broken leg, so I fixed and right now I have grey screen see picture. This screen is without signal from atari st. I tried to adjust all 5 adjustable resistor, but no luck (with and without signal). When signal is give there is some change in sync. My monitor is 110v, my atari is 220v, but I'm using improved TOS switching between 50Hz/60Hz there some difference on screen, but I wasn't able to see any picture that at least I can recognise it's always grey. I'm not electronics hobbies and it's first time when I'm trying to fix CRT monitor. I scan repair manual and I don't recognise flow which match to this. As I understand in case of missing sync I should see something and in case of missing signal screen should be black, but not in my case. Any hint is welcome, what is worth to check? I googled a lot, but found one similar case, but not solution there, discussion at the end was about signal for atari st. Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/ Share on other sites More sharing options...
TGB1718 Posted April 20, 2022 Share Posted April 20, 2022 With no signal, that looks like the tube is being overdriven (brightness circuit), apart from the normal control on the front, there should be some adjustment of the coarse brightness. Could also be caused by tube avoervoltage but that requires specialist equipment to check. Look for any adjusters around the HT circuit, please don't do this with it powered, any adjustment should be done with long plastic screwdrivers, if your not sure, would be best to see if there's someone who can still fix these things. 1 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5044306 Share on other sites More sharing options...
Paweł Posted April 21, 2022 Author Share Posted April 21, 2022 Hurry, monitor back to live. Issue was R363 (except of adjustable resistor). 5 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5045197 Share on other sites More sharing options...
Albert Posted April 21, 2022 Share Posted April 21, 2022 Nice work! 1 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5045199 Share on other sites More sharing options...
tjlazer Posted May 21, 2022 Share Posted May 21, 2022 How were you able to find the fault? 1 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5061496 Share on other sites More sharing options...
Paweł Posted May 21, 2022 Author Share Posted May 21, 2022 Yes, please check 3rd post in this thread (#3) Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5061498 Share on other sites More sharing options...
Tillek Posted May 21, 2022 Share Posted May 21, 2022 2 hours ago, Paweł said: Yes, please check 3rd post in this thread (#3) Actually, the question (I believe) was what steps did you take to narrow down the problem. I think that would be something of interest as troubleshooting monitor issues is probably a weak point for most of us here. 1 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5061579 Share on other sites More sharing options...
SviRu Posted October 9, 2023 Share Posted October 9, 2023 On 4/20/2022 at 8:43 AM, Paweł said: I'm trying to fix my old SC1224 (goldstar ca-3) monitor which was in basement around 20 years ;-). I know that it was faulty when it was stored. Root cause was as kid I broke V.Lin adjustable resistor (R635) and it was replaced by someone who at that time had TV repair shop ;-), but still not working. I run it and it was looks like that V deflection is not working (big white line on the screen). I figured out that V.Size adjustable resistor (R616) had broken leg, so I fixed and right now I have grey screen see picture. This screen is without signal from atari st. I tried to adjust all 5 adjustable resistor, but no luck (with and without signal). When signal is give there is some change in sync. My monitor is 110v, my atari is 220v, but I'm using improved TOS switching between 50Hz/60Hz there some difference on screen, but I wasn't able to see any picture that at least I can recognise it's always grey. I'm not electronics hobbies and it's first time when I'm trying to fix CRT monitor. I scan repair manual and I don't recognise flow which match to this. As I understand in case of missing sync I should see something and in case of missing signal screen should be black, but not in my case. Any hint is welcome, what is worth to check? I googled a lot, but found one similar case, but not solution there, discussion at the end was about signal for atari st. I have very similar problem. Grey screen only. sc1425 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5330544 Share on other sites More sharing options...
CommodoreDecker Posted October 11, 2023 Share Posted October 11, 2023 (edited) On 5/21/2022 at 2:00 PM, Tillek said: Actually, the question (I believe) was what steps did you take to narrow down the problem. I think that would be something of interest as troubleshooting monitor issues is probably a weak point for most of us here. Based on post 1 and wanting to take a wild pot shot guess, and I'd have to find the schematics, I would surmise that R363 might pertain to the brightness part of the circuit? Given the number of resistors on the circuit board, it's not quite a needle in a haystack but approaching it... resistors don't go bad as often but it does happen, of course... yay for entropy! I'd probably replace the capacitors on the board as well for good measure as well - after ensuring they're all discharged... Edited October 11, 2023 by CommodoreDecker 1 Quote Link to comment https://forums.atariage.com/topic/334469-sc1224-grey-screen-with-lines/#findComment-5331387 Share on other sites More sharing options...
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