low width and pincushion

hi there again!

Could anyone help me out this monitor?

NTC, model No: KM-411 The problem is low width and pincushion. It also has slight breathing. I checked diodes, and transistors in the horizontal and pinamp area but

not found the culprit. Check coils by substitution but still no effect.

Comparing the voltage from a known good monitor, I discovered that this

one has low B+ output. Measured from flyback primary winding, the good monitor has 200 volts. But the defective one has only 170 volts. Anyway, I have tested capacitors with my ESR meter in the psu and horizotal. They seem okay. Disconnecting flyback primary winding creeps

up the voltage to 215 volts. Does it mean the problem lies on the horizontal section and not on the low voltage power supply section? Where should I look now. It seems I'm lost.

Thanks in advance for troubleshooting tips.


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Hi, Ian. Please post this at sci.electronics.repair. You'll have a better chance of getting a good answer.

Good luck Chris

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good day! thanks for the advise. I've originally posted this in sci.electronics.repair but with no replies. Tha't why I tried it here. Thanks you responded.

Before I post this message, I've already found the problem. It's the flyback. Substituted it by a known good one and the set was fixed. I just dont know why flyback fails this way. I guess its defective internally. Maybe partially shorted or open. I am not sure. Its because when i disconnect the B+ supply in the primary winding of the flyback before the problem was solved, the voltages in the horizontal section creeps up to 200 volts.

So if someone encounters this problem, NTC, Model No: KM-411, if after checking yokes, capacitors esr and capacitance and other components especially in the low voltage psu and horiz section reveals nothing, a big chance its the flyback breaking down when under load.

ian b. (philippines)

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