Maker Pro
Maker Pro

? 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.
 
J

Jumpster Jiver

Jan 1, 1970
0
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:

http://img519.imageshack.us/img519/8052/commodoremonitorverticaby1.jpg
http://img519.imageshack.us/img519/8156/commodoremonitorverticaws8.jpg
http://img519.imageshack.us/img519/2538/commodoremonitorverticapm3.jpg


Thanks again.

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.
 
S

Sam Goldwasser

Jan 1, 1970
0
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:

http://img519.imageshack.us/img519/8052/commodoremonitorverticaby1.jpg
http://img519.imageshack.us/img519/8156/commodoremonitorverticaws8.jpg
http://img519.imageshack.us/img519/2538/commodoremonitorverticapm3.jpg

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.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
 
F

Franc Zabkar

Jan 1, 1970
0
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.

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
 
N

n/a

Jan 1, 1970
0
On Fri, 29 Jun 2007 09:48:19 -0700, [email protected] put finger

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.

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.
 
N

n/a

Jan 1, 1970
0
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.
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.
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.


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.
 
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