IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
 

G'day folks, I have an IBM P70 (Type 6554-674) that no matter what
display mode I choose, (640*480 - 1600*1280), it always has approx.
30-35mm of each side of the screen unused when the horizontal size is
adjusted to %100. Vertical size is fully adjustable to the viewable
area limits.

I've tried different computers, (including one that will allow me to set
vert/horiz. frequencies other than the standard, the full range that the
monitor is capable of), and it still will not allow a full width picture.

If I turn up the brightness sufficiently I can see the raster edges end
approx 20-25mm from the edges of the viewable area, with the output
display ending approx 15mm short of that, if you know what I mean.
The output display is fully positional within the raster area.

Crappy ASCII pic follows, (haven't bothered showing top/bottom):

Screen edge Screen edge
v v
| 20 |15| |15| 20 |
| mm |mm| Display |mm| mm |
| | | output | | |
^ ^
Raster edge Raster edge

Would this possibly be because of reduced horizontal drive?

I have a Service Manual for the GDM-17SE2T, (has some minor control
differences), but before I got into the guts of the thing I was
wondering if anyone had any ideas?

TIA,
Dave

IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
 

Dave:
I have had some experience with this problem on Dell/Sony GDM-17SE2T
monitors. Behind the flyback, there is a small transformer in location
T403. Mine had the number 998-11 on it.
These transformers develop small cracks in the core that is on the
outside of the windings. This somehow affects the horizontal width.
I had two monitors with narrow widths. Replacing the transformers
with ones from junked chassis fixed the problem.

There is also another transformer in location T701. This one can
develop cracks too, but it controls the dynamic focus. You can
have good focus in the center, but be out-of-focus on the edges, or
vise-vera.
Hope this helps...
John

IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
 

John Gill wrote:
Dave:
I have had some experience with this problem on Dell/Sony GDM-17SE2T
monitors. Behind the flyback, there is a small transformer in location
T403. Mine had the number 998-11 on it.
These transformers develop small cracks in the core that is on the
outside of the windings. This somehow affects the horizontal width.
I had two monitors with narrow widths. Replacing the transformers
with ones from junked chassis fixed the problem.

Thanks John, I'd just put the D board into service position and was
about to check the B+ and associated items mentioned in Sam's Repair FAQ.

This will give me something else to look for, it might even be the real
cause, (ruling out caps, etc), since the width does not vary with
temperature, (just ~50mm too small).

There is also another transformer in location T701. This one can
develop cracks too, but it controls the dynamic focus. You can
have good focus in the center, but be out-of-focus on the edges, or
vise-vera.

Focus seems to be OK so far, though of course it hasn't gone to full
width yet.

Hope this helps...
John

Thanks again,
Dave

IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
 

John Gill wrote:
Dave:
I have had some experience with this problem on Dell/Sony GDM-17SE2T
monitors. Behind the flyback, there is a small transformer in location
T403. Mine had the number 998-11 on it.
These transformers develop small cracks in the core that is on the
outside of the windings. This somehow affects the horizontal width.
I had two monitors with narrow widths. Replacing the transformers
with ones from junked chassis fixed the problem.

Just a followup John, after checking the voltages and finding them
spot-on, I pulled T403 and had a good look at it - sure enough a small
crack. When I eased off the tape around it a section of the core
dropped off.

So thank you very, very much for sharing this with me, (and the rest of
us), this would have saved me hours checking resistors, ESR on caps, etc.

I only hope I can get a replacement now, (either the whole thing or
poss. the cores).

Thanks again,
Dave

IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
 

John Gill wrote:

Dave:
I have had some experience with this problem on Dell/Sony GDM-17SE2T
monitors. Behind the flyback, there is a small transformer in location
T403. Mine had the number 998-11 on it.
These transformers develop small cracks in the core that is on the
outside of the windings. This somehow affects the horizontal width.
I had two monitors with narrow widths. Replacing the transformers
with ones from junked chassis fixed the problem.

ARRGGHHH!! I had high hopes for this but unfortunately replacing the
relevant T403, (which had a cracked core), hasn't resolved the problem -
the raster is still 50-60mm too narrow, so back to the drawing board.

Dave