Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Bennett Price
 
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Default Focus problem on old VDT

I've got a NEC Multisync-II VDT (JC-1402HMA), about 10-15 years old.
Brightness and contrast are OK, not stunning. But when cold, it's badly
out of focus and becomes acceptable after ~10 minutes as it warms up. I
can twiddle the focus adjustment to get good focus when cold but then
focus is bad when warm. Brightness/contrast don't appear to change much
as it warms up.

Is there any particular component or two which would fix the problem?
I've got the service manual so I won't be totally in the dark.

Thanks
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JANA
 
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Default Focus problem on old VDT

Common causes are from the high voltage multiplier, and the CRT itself is
going weak. The high voltage multiplier may be a separate module, or
combined with the flyback, depending on the chassis type.

As components age, some may become thermo sensitive, and change their
specifications with temperature, age, and use.

Depending on the exact nature of the fault, this monitor will most likely
not be worth for to have it serviced.

--

JANA
_____


"Bennett Price" wrote in message
. ..
I've got a NEC Multisync-II VDT (JC-1402HMA), about 10-15 years old.
Brightness and contrast are OK, not stunning. But when cold, it's badly
out of focus and becomes acceptable after ~10 minutes as it warms up. I
can twiddle the focus adjustment to get good focus when cold but then
focus is bad when warm. Brightness/contrast don't appear to change much
as it warms up.

Is there any particular component or two which would fix the problem?
I've got the service manual so I won't be totally in the dark.

Thanks


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Yukio YANO
 
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Default Focus problem on old VDT

Bennett Price wrote:
I've got a NEC Multisync-II VDT (JC-1402HMA), about 10-15 years old.
Brightness and contrast are OK, not stunning. But when cold, it's badly
out of focus and becomes acceptable after ~10 minutes as it warms up. I
can twiddle the focus adjustment to get good focus when cold but then
focus is bad when warm. Brightness/contrast don't appear to change much
as it warms up.

Is there any particular component or two which would fix the problem?
I've got the service manual so I won't be totally in the dark.

Thanks

Bad filter capacitor in focus voltage/high voltage stage ?? pulling down
focus/high-voltage voltage.

Yukio YANO
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