Who are the experts in XY monitors?

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

I thought I was pretty good with these old B&W XY monitors
until I received a tough one for repair. The problem is that
there is something loading down the B+ (+40VDC) line;
the B- is okay. If the yoke is unplugged or if the deflection
transistors are unplugged, the B+ is correct. The bad board
is a Well Garner deflection PCB; I'm using a 15" Electrohome
chassis to attempt repairs with. I know there are differences
between the 15" and 19" yokes, but would it be enough to
cause too much loading on the B+? I'm pretty sure the answer
is no, but correct me if I'm wrong. The B+ is still too low
(but not quite as low) if the yoke is plugged in, but only
one set of the chassis mounted transistors are plugged in;
doesn't matter which set is left plugged in; still gets loaded
down. I plan to check the MPSU deflection transistors next;
any other ideas?

Best Regards,

John Hermann
Buy, Sell, Trade, and Repair Video and Pinball Machines.
Located near Dallas, TX.
http://www.geocities.com/SiliconValley/Circuit/8393

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Try replacing the zener diodes. I have come across 2 BW XY's and 3
color XY's that had low b+ voltage and the zener diodes in the HV cage
were the culprits.
Cody

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Are you sure the yoke itself isn't leaking?

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

John Hermann <jhermann@hifi07.dal.design.ti.com> wrote:
: I thought I was pretty good with these old B&W XY monitors
: until I received a tough one for repair. The problem is that

Check the veectorlist archives:
http://www.vectorlist.org/

And secificly the BW vector faq:
http://www.vectorlist.org/Documents/bw_vector_monitor_faq.pdf

This isn't a particular problem I remember, but the archives are index, if
it ever came up it will be there.

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