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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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Help for Monitor ADI PD-959 dead!
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 |
#2
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Help for Monitor ADI PD-959 dead!
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 |
#4
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Help for Monitor ADI PD-959 dead!
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