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roj_matt

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  1. Techknight, chalk another one up to your number of SE/30s saved. I replaced UE8 with a new 74LS166AD, and my video is like new again! Thank you thank you!
  2. So I successfully replaced UC6 and UC7 with MT42C4064-12 chips. After all the soldering and desoldering, I was excited to hear the familiar chime after all was said and done, but was extremely disappointed that the problem persists. In fact, I'm wondering if there might be multiple issues. White or black pixels still track cursor and window movement on the screen, but there is also a lot of pixel flickering. It kind of reminds me of "snow" on old analog TVs when a TV signal is weak. The other strange thing is that this flickering matches hard drive activity. So there seems to be an electrical issue somewhere. Since I can't seem to upload video files, here is a Dropbox link to a video that shows what I'm seeing: https://www.dropbox.com/s/t92izeq7j80jzuu/se30_pixel_issues.mp4?dl=0 I have a working SE/30, and I see the problems when I install the board into either machine. Any help or suggestions are greatly appreciated! My wife is wanting me to downsize my vintage computer collection, and I need to find a good home for this SE/30, but I'd like to get it working like new again, and not make this someone else's problem.
  3. Thanks! I found MT42C4064-12 chips on eBay, but not the MT42C4064-15 (which are currently used on the board). Comparing spec sheets, the only difference I can see is max access time (120 ms vs 150 ms). Is it safe to assume that the -12s will work just in place of the -15s?
  4. So there are one or two SE/30s on eBay for parts only. I'm considering buying one just to get the VRAM chips. I'd prefer to buy the chips directly if they are available, to avoid the risk of buying a broken machine that won't fix my problem. Does anyone know if they are still available somewhere? My usual electronics sources (Mouser, Jameco) don't stock any, which makes me think that the chips aren't made any more.
  5. I checked continuity with all 24 pins on UC6 and UC7, and everything tested ok. As techknight and Paralel have stated, it must be bad VRAM (which means UC6 and/or UC7 may need to be replaced...). I was REALLY hoping it would be a bad trace, or something like that that's easy to fix... What am I up against here? It seems like the most difficult thing here would be acquiring 2 replacement ICs for UC6 and UC7. My initial Google searches reveal that these chips aren't easy to come by (but I could be wrong). I've sifted through some of the other topics, and apparently you have replaced VRAM chips before. Do you know where I can find these chips?
  6. Thanks, apm! I'm an idiot. So seeing that you mentioned that it sounds more like a digital problem than an analog problem, I went back and swapped logic boards between my working and semi-working machine, just to double check. The problem followed the logic board. I could have sworn that I tried this bad board in my other machine.... So this really is a digital issue. I will check the address lines and report back.
  7. I recently recapped and refurbished an SE/30 to the point where the sound is loud and clear, and everything else seems to work great except for the display itself. During my refurbish process I replaced the CRT, as the old one had severe burn-in. Things appear much clearer on the new one, but random artifacts appear on the screen. As you can see in the photo, there are some white pixels right by the mouse pointer, the MacintoshHD window (and its icon) and other places on the screen. As I move the mouse pointer or drag the window elsewhere, the pixel artifacts follow the movement. I also get flickering pixels (not visible in the photo) that get worse the longer I have the machine powered on. It kind of looks like there is some kind of interference, but I don't have any other electronics powered on nearby. I'm pretty sure something is faulty on either the analog board or the yoke/CRT, or both. I have a working SE/30 that I've used to test this machine's logic board, and it works great. I haven't replaced any components or done anything else on the analog board--it's in the same state as when I received this machine. I did try adjusting the focus, cut-off, height, etc. No change. I've visually inspected the analog board, and there are no obvious smoking guns (leakings caps, cracked solder joints, residue, etc.). I've read up on other posts where replacing the flyback transformer fixed certain display issues (but none of the issues I can find are exactly like mine). Can someone confirm that this might be my problem? Any other ideas where I should start as far checking/replacing components?
  8. I guess you're "techknight" for a reason. I replaced the op-amp and once again the sound is working loud and clear! Thank you! I have searched these forums over and over looking for people whose SE/30s had similar symptoms to mine, and haven't found any that quite matched. Hopefully this thread helps someone else. So to summarize what I did to fix this issue: - after a successful recap, the sound mysteriously faded to static (completely unrelated to the new ROM chip I happened to install at the same time) - performed continuity tests between capacitors (c1 - c10) and the Sony sound chips (everything checked out) - used a DMM (digital multimeter) on diode test mode to test the Q1 NPN and Q2 PNP transistors; Q1 was in doubt - I replaced Q1 (didn't fix the problem) - I then replaced the op-amp chip (UA9 on the board) That did the trick! No more static! The power-on chime is loud and clear!
  9. So I ordered a few MMBT3904 transistors. I removed the old one and soldered the new one on. I now get readings with the resistance check, but still just static (no sound). I didn't see your updates to this post until after I had already removed the old transistor. You mention testing it with a diode check is the only accurate way to do it, so now I'm doubting I was even testing it correctly to begin with... Most online tutorials have you test a transistor using resistance (the negative lead on the emitter or collector, positive on the base should give you numbers in the MOhms). I have a diode test mode on my DMM, but I'm not sure what I'm looking for. The numbers I get are in volts instead of ohms... As you can see, I'm confused. Do you know the part number for the op-amp? The writing on it says "TL071B 804". There appear to be a few different TL071B chips out there. Anyway, now that my original diagnosis is in question, is replacing the op-amp still the next best thing to try? I'm not quite ready to give up yet, but just out of curiosity, what is the typical going rate for you or others to troubleshoot and fix boards?
  10. So I think I've narrowed the problem down to the Q1 NPN transistor. Comparing this board side by side to one of my working boards, I get no resistance readings between emitter (-) and base (+) nor between collector (-) and base (+) on my broken board. The same readings on my working board look normal (numbers in the MOhms). The Q2 PNP transistor tests the same on both boards. I'm not familiar with the component specs. The lettering on it says "1A." I searched for 1A surface mount NPN transistors, and found some. Unfortunately they come in 10K, 22K, and 47K varieties (on Amazon). Do you know the kind of transistor I'll need? Are there different transistors that might be better? Thanks!
  11. Ok, so I found the schematics and did continuity tests. I tested the address lines between UE10 and UK6 (as well as UJ11, and UI12). Everything checks out fine. I also checked for continuity from the Sony sound chips (UB10 and UB11) to UE10. All is well there too. Do you have any other suggestions?
  12. Thanks, Doug! The verdict is...the ROM chip works great in my other SE/30! Previously I didn't dare try it in another machine for fear of breaking it too. Now that that's out of the way, I need to find schematics, pull out my multimeter and start testing continuity.
  13. Since I'm convinced at this point that your chip has nothing directly to do with the sound issue, I'll try it in my working SE/30... (crossing my fingers)
  14. Thanks, techknight! Pardon my ignorance, though it was easy enough to identify the 8530 and the 53C80, I'm not sure which chip is the ASC. What is the location of that chip (as printed on the board)? I can track down some schematics and test continuity between the chips (in fact, if anyone has a link to a good copy of the schematics, that would be fantastic). I haven't experienced any freezes, crashes or address errors. As I mentioned previously, aside from the sound, everything seems to work perfectly.
  15. I haven't been so bold as to put the board in the dishwasher, as some people have done. I did try to clean the board with rubbing alcohol and Q-tips.
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