nicktasios
Member
Last Activity: 12-23-2024, 02:22 AM
Joined: 09-16-2023
Location: Eindhoven
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Macintosh Quadra 840AV PSU
I had my Quadra 840AV (which I recapped and had working) plugged in for some time without using it and randomly decided to turn it on today. Unfortunately it did not turn on. After checking the PSU, I found out I was not getting anything from 12V, only from the 5V rail. After a few minutes, I removed the PSU and plugged it back in the electrical outlet and it suddenly started making a weird sound and soon after smoke started coming out. I quickly unplugged it. I opened it up but on first instance I didn't see anything out of the ordinary really. I later turned it back on and one of the MOVs blew... -
Re: Troubleshooting Apple Multiple Scan 17 Display
Oops, my bad! I had two cables switched around. I was always wondering what these cables were for so I checked the markings on the power board and they are labeled as 'rotation' and 'v.stat'. So I swapped the cables around and presto! After resetting the settings, the convergence problems are mostly gone. There are still slight geometry issues, but I'm afraid I'm not experience enough to mess with the more advanced yoke adjustments. How are these normally adjusted? Do I need a pattern generator or can I just put some images fullscreen?... -
Re: Troubleshooting Apple Multiple Scan 17 Display
The replacement component finally arrived! Unfortunately they forgot to ship it so it took a week longer to receive. I immediately replaced it and was ready to be disappointed, but I'm happy to report that it worked brilliantly!
On the other hand, I noticed quite a bit of a convergence issue as you can see in the first few pictures, so I tried to fix it with the buttons on the front panel. To my surprise, the vertical convergence button did little, and I noticed it actually rotated the screen a little instead of doing...Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
No problem! I'm also doing renovation in the house in the meantime. I'm really grateful for the help, it sounds like you really know a lot about CRTs and helping me just from the pictures. I have to shine a light through the board to find out where all the traces go!
Sorry, I meant VPS07T, not LS07T. Here is the datasheet[URL="https://pdf1.alldatasheet.com/datasheet-pdf/view/88418/SANYO/VPS07.html"]https://pdf1.alldatasheet.com/datasheet-pdf/view/88418/SANYO/VPS07.html[/URL]. This one is for...Last edited by nicktasios; 10-03-2023, 03:36 AM.Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
So, this becoming more of a repair log, but hopefully someone might benefit from it in the future.
After the last post I spent like 12 hours trying to figure out what the problem was. I removed the transistor Q204 on the green line and then got the expected readings on D209, so I thought that the transistor was the problematic part. In diode mode it was reading fine so I decided to swap it with the one from the red line, Q104. Alas, the problem was exactly the same. I then swapped D209 with D109, but again the same....Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
I went ahead and removed IC001 from the board, and (un)fortunately it was not the component causing the problems, so I went ahead and removed IC002 too, but again, the difference in the diode readings remained.
The remaining circuit for each of the R, G, and B is not that big, so I mapped them. In the attachment I show two separate schematics for the R and B parts. You see that some parts are the same, and in reality, the RGB parts are connected at these points (note that there are some other capacitors connected between...Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
I made some progress! The nice thing with these neck boards is that in principle the red green and blue parts of the board should actually be clones of each other. So I put my multimeter in diode mode and checked the pins R.In, G.In, and B.In, and found that R and B were reading the same (0.66V), but G was different (0.86V). This leads me to believe that there is a faulty component somewhere along the green part. Following the path with my multimeter, I end up at IC001 (R and B reading 0.56V and G reading 1.28V). If I'm understanding...Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
I reflowed the solder joints as you suggested, and then some, but unfortunately I still get a purple screen. Not sure if it's related to the reflowing or not, but now it doesn't seem to get its color back and convergence somehow became worse (look attachment).
I then went ahead and replaced C062, C201, and C007, since I had replacements at hand, but unfortunately that didn't have any effect.
Maybe worth mentioning, the monitor has adjustments for horizontal and vertical convergence. Horizontal adjustment...Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
I posted images of the boards here [URL="https://imgur.com/a/VbrZR9i"]https://imgur.com/a/VbrZR9i[/URL] . Below I attached an overview of the two main boards.
The capacitors are mostly Matsushita, with some ELNA, Rubycon, and I think some Nippon Chemi-Con.Re: Troubleshooting Apple Multiple Scan 17 Display
I posted images of the boards here [URL="https://imgur.com/a/VbrZR9i"]https://imgur.com/a/VbrZR9i[/URL] . Below I attached an overview of the two main boards.
The capacitors...Last edited by nicktasios; 09-25-2023, 02:36 PM.Leave a comment:
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Re: Troubleshooting Apple Multiple Scan 17 Display
Funny that you ask, but indeed, the monitor gets back its color suddenly. I disassembled the monitor completely and inspected both boards thoroughly and I found that they looked superb, shiny pads, no leakage close to caps nor any bulging. Close to the flyback transformer it's a bit darker, I guess from dust and heat. I did clean both boards from the accumulated dust.
I didn't find any cracked joints, but I guess these are often tricky to detect with the naked eye.
If I post some pictures could you...Leave a comment:
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Troubleshooting Apple Multiple Scan 17 Display
I recently picked up a Quadra with a Apple Multiple Scan 17 Display. The Quadra was not working, it clearly had corrosion from leaking caps so I replaced them and luckily it chimed and worked properly.
The next problem to tackle was the screen. Sometimes it turns on and off multiple times before finally turning on, and then it sometimes turns purple. After waiting some time, without doing anything, it regains all colors. Another symptom is that it sometimes seems to momentarily blink.
Also, not sure if this is related, but sometimes, after experiencing these problems,...Last edited by nicktasios; 09-17-2023, 03:54 AM. -
Re: New Members - please post your introductions here
Hi everyone. I'm Nick, AI scientist, and like to tinker with old machines. I started repairing old electronics with the Game Gear, which I got from a friend, I guess over 10 years ago. Unfortunately I was never able to repair that one. I probably caused a short, frying one of the ICs while troubleshooting. Now I have repaired a few consoles and PCs, but I'm still learning and I can use the help of more experienced tinkerers.Leave a comment:
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