Help for Monitor ADI PD-959 dead!

B

bricoman

Guest
Hi, i'm italian (sorry for my not good english) and i've a problem
with my
monitor.
This is a post about a problem whit my ADI PD-959 monitor and is EQUAL
to other question posted. I' d0't know if the other freinds had fixed
the fault.
Can anyone help me, please?


The monitor had Q831 shorted. I'd replaced with another BU2508DF but
not run yet. The green LED are lit all rthe time and both degauss and
vertical deflection works. The components around the Q831 (resistencs,
diodes ecc) are good and the B+ is present. The The FET Q563 (IRF740)
is good too (i changed it to test). With the scope i see a signal, 4 V
peak to peak, at the base of the HOT. The measured voltage, respect to
ground, both B, C and E starts initially
with approx 90V slowly raising to approx 220VDC over a period of
2,3 minutes; is correct this?
I've not the schematics or other information about, and i do't
know to do to fix the problem.
Many, many thanks for your attention
Regards
Alberto Malfatti
 
Alberto:
I would check the high-voltage transformer(flyback) next.
My flyback test is as follows:
1. Measure the resistance from the HV anode to ground. It should
read open circuit. Any resistance ususally means it is bad.
2. Check the capactance from anode to ground. It should read about 2.5
to 3 nano-farads. I usually assume 1.5 to 5 is OK.
3. Check the primary winding with a flyback ring tester.

Also
4. Check any electrolytic capactors near the horizontal driver transformer.
5. Check for any shorted FET's or bad electrolytic capacitors in the
circuit that supplies the B+ voltage to the flyback (and HOT).
Note: these tests will not always find a bad flyback.

Hope this helps...
John
 
Bad flyback causes the HOT to short, its a common problem, I've got a unit
here with a problem with the SMPS (blows fuse, problem in the module,
switcher transistor shorted, problem remained after replaced, couldn't find
anything else) I'm going to take anther crack at it after winter. The
resistance test should prove the flyback answer (I'm 75% sure when they go
bad they show this characteristic). If you decide to get rid of it instead
of fixing it I would like to buy it for parts. If interested email me at
JDC@CNYCONNECT.NET good luck.

-glasnostJDC

"bricoman" <albmalf@tin.it> wrote in message
news:1197771b.0309182223.98e5b26@posting.google.com...
Hi, i'm italian (sorry for my not good english) and i've a problem
with my
monitor.
This is a post about a problem whit my ADI PD-959 monitor and is EQUAL
to other question posted. I' d0't know if the other freinds had fixed
the fault.
Can anyone help me, please?


The monitor had Q831 shorted. I'd replaced with another BU2508DF but
not run yet. The green LED are lit all rthe time and both degauss and
vertical deflection works. The components around the Q831 (resistencs,
diodes ecc) are good and the B+ is present. The The FET Q563 (IRF740)
is good too (i changed it to test). With the scope i see a signal, 4 V
peak to peak, at the base of the HOT. The measured voltage, respect to
ground, both B, C and E starts initially
with approx 90V slowly raising to approx 220VDC over a period of
2,3 minutes; is correct this?
I've not the schematics or other information about, and i do't
know to do to fix the problem.
Many, many thanks for your attention
Regards
Alberto Malfatti
Click to expand...
 
Ok. Many thanks for your suggestion.
I will try.
Thanks
Alberto



albmalf@tin.it (bricoman) wrote in message news:<1197771b.0309182223.98e5b26@posting.google.com>...
Hi, i'm italian (sorry for my not good english) and i've a problem
with my
monitor.
This is a post about a problem whit my ADI PD-959 monitor and is EQUAL
to other question posted. I' d0't know if the other freinds had fixed
the fault.
Can anyone help me, please?


The monitor had Q831 shorted. I'd replaced with another BU2508DF but
not run yet. The green LED are lit all rthe time and both degauss and
vertical deflection works. The components around the Q831 (resistencs,
diodes ecc) are good and the B+ is present. The The FET Q563 (IRF740)
is good too (i changed it to test). With the scope i see a signal, 4 V
peak to peak, at the base of the HOT. The measured voltage, respect to
ground, both B, C and E starts initially
with approx 90V slowly raising to approx 220VDC over a period of
2,3 minutes; is correct this?
I've not the schematics or other information about, and i do't
know to do to fix the problem.
Many, many thanks for your attention
Regards
Alberto Malfatti
Click to expand...
 
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