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? Fixing Vertical Deflection Problem on Old Screen

Hi,

I've got an old Commodore monitor that's been having some problems for the past several months. Sometimes it's fine but more and more often, the picture shrinks to a few lines in the middle of the screen.

These past two weeks have pretty much confirmed what the problem is since last Monday (when it was hotter than Hell), it worked fine for a few days but stopped during the weekend (when it cooled down a lot), and then the same pattern repeated this week.

Obviously the vertical deflection circuit has developed a problem, either a bad (thermo-sensitive) capacitor, or perhaps just a loose connection (solder joint).

I haven't cracked it open since figuring out what the problem likely is, but I hope to finally fix it this weekend. I just don't know what to look for in this old thing. I am hoping that someone can advise me of what to look for and an effective technique for pinpointing the problem area. Pictures are more than welcome. In fact, I will try to take a photo of the area and post it.

Thanks a lot.

Reply to
googroups
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Okay, I've taken a few shots of the yoke and surrounding area. I tried to clean them up a bit, but this camera's not very good. I hope they help.

It's 764KB for the three:

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Thanks again.

Reply to
googroups

The vertical deflection is not on the CRT board, it's on the main board. It might be marked "VERTICAL", "VERT", etc. THere should be an IC and several small capacitors. Replace the caps, resolder the ICs, everything should be fine. I can't tell for sure but the IC mounted to a heat sink under the front of the Yoke could be it.

Reply to
Jumpster Jiver

Sounds like cracked solder joints on the mainboard. Trace the 4 wire cable from the deflection yoke to the mainboard connector. It may even be right there.

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Reply to
Sam Goldwasser

On Fri, 29 Jun 2007 09:48:19 -0700, snipped-for-privacy@hotmail.com put finger to keyboard and composed:

There are four wires going to the yoke. Two will be for the horizontal, and the other two for the vertical. Follow them back to the PCB. The thicker (?) wires are probably the horizontal.

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.
Reply to
Franc Zabkar

Thanks for the tips Sam and Franc. There is a four-wire connector that goes from the yoke to the board. The red wire is the thickest, and the other three are the same.

I traced it on the PCB and looked around but could not find an obvious bad joint. I poked a bit at the board and the various connections in the area with a rubber pointer and it occasionally did work for a moment, but I was unable to identify one concretely.

Here's a shot of the area. The connector is the vertical strip just to the right of center, next to the box (the first three are the thin wires, the fourth is not connected, and the bottom is the thick red). I could not find any labels identifying the vertical deflection, or any ICs or caps in the area.

I should also point out that there seems to be a lot of yellow, crusty materials on and around the board. Some of the components seem to be glued in place by some yucky old-and hardened-gunk (almost like it has leaked out from the bottom), and there are other splotches on various places. Some of it may be residual flux, but others are not. I considered cleaning some of it, but decided against it for now.

I also called around town and there was only one place that said they could/would fix it, but it would cost a ridiculous amount. I'm going to end up having to fix it myself because I can't afford to have someone fix it, and I don't want to just replace it (assuming that I could afford to) because it's an authentic C64 monitor for an authentic C64-assuming that I can find the console, disk drive, etc. in the basement.

Reply to
n/a

Thanks for the tips everyone. There is a four-wire connector that goes from the yoke to the board. The red wire is the thickest, and the other three are the same.

I traced it on the PCB and looked around but could not find an obvious bad joint. I poked a bit at the board and the various connections in the area with a rubber pointer and it occasionally did work for a moment, but I was unable to identify one concretely.

Here's a shot of the area. The connector is the vertical strip just to the right of center, next to the box (the first three are the thin wires, the fourth is not connected, and the bottom is the thick red). I could not find any labels identifying the vertical deflection, or any ICs or caps in the area.

I should also point out that there seems to be a lot of yellow, crusty materials on and around the board. Some of the components seem to be glued in place by some yucky old-and hardened-gunk (almost like it has leaked out from the bottom), and there are other splotches on various places. Some of it may be residual flux, but others are not. I considered cleaning some of it, but decided against it for now.

I also called around town and there was only one place that said they could/would fix it, but it would cost a ridiculous amount. I'm going to end up having to fix it myself because I can't afford to have someone fix it, and I don't want to just replace it (assuming that I could afford to) because it's an authentic C64 monitor for an authentic C64-assuming that I can find the console, disk drive, etc. in the basement.

Reply to
n/a

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