Tech : Electrohome G08-003 image too big

I’m in the beginning of the process of restoring my Star Trek Captain’s
Chair:
http://www.austinmodders.com/modules.php?name=Forums&file=viewtopic&t=2724

having purchase an untested board set and an untested G08 Electrohome
monitor.

My goal is to verify the boards / monitor as good before I being the
recapping process.

I verified the board set as working after some initial debug - displaying
the vector graphics on my Oscope (see thread above).

I received a untested G08 by Fedex ground a week or so ago and began
debugging it Sunday. Initially; the monitor did not power up; and I detect
both F400 and F401 as blown. I immediately checked the Deflection
transistors and detected two of the transistors were shorted. I replaced
them with NTE388 (subs for MJ21196G according to Bills Classic Arcade
http://www.biltronix.com/Star_Trek_08.html ) on a quick run to Frys
Electronics.

I replaced the F4xx fuses with 4A Slow Blow as suggested by Bill and
F700/600 with 2A slow blows.

The monitor powered up and is vectoring the game; however, it only appears
to be rendering a "zoomed in" image. IE I can see part of the sega banner
and other graphics such as the plasma shots coming from the Klingons in
attract mode.

I've checked the transistors in the deflection portion of the deflection
board and they seem to be good based upon the dmm diode test.
I've measured most of the voltages except HV. +9.1 is a little low at 8.5V.
+400 is low at around 350V but varies based upon vector images. But unsure
that those would be the cause of the image issue.

I'm not 100% sure as it's difficult to determine but it looks like the
horizontal MAY be ok / unzoomed... and only to vertical is zoomed.

I'm looking for suggestions as to what to check.
John

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Received on Tue Feb 22 22:44:22 2011