Re: identical G05-802 problem with 2 different deflection PCBs

On 14 Dec 2009, at 01:45, John Robertson wrote:

> Colin O'Brien wrote:
>> FInally got some spare time to check this out today. The voltage at G1 is climbing, others (G2 etc) are stable.
>>
>> Thoroughly inspected the board but all components check out ok, even replaced a few just to be sure. The thing is this voltage increase seems to be coming into the board from G1.
>>
>> If I set both pots to 0, I start out with 0V at Pin 2 of P500 (G1). Then it starts climbing, I remain at 0 or close to 0 on the pot side of R518 but on the P500 side it keeps growing to about 50V when I cut it off to avoid damage. At that point everything is very bright and retrace lines are visible. A quick check to other pins shows no change.
>>
>> Not sure where to go from here.
>>
>> Thanks,
>> Colin
>>
>>
> This sounds like a problem with the HV section. Can you pull it out and set it on the bench and feed it 35VDC to see if the HV and other voltages are stable? I put the HV lead into a ceramic cup to avoid shocks, and leave a HV probe touching it to monitor the HVDC...if it changes, turn off the HV and then feel the HV diode - as it is not connected to a picture tube there will be no stored charge - it should only be around room temperature or warm to the touch, hot means it is bad.
>

I'll give it a go. Thanks for the testing tips.

> A quick side question - are you sure that you are using two IDENTICAL monitor boards? Electrohome and Wells Gardner both made B&W chassis that look similar but (AIR) can't be plugged into the others chassis.

Yes, they're exactly the same model and same revision. There's an electrohome logo on the back, the only difference is the soldermask colour.

Thanks,
Colin

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Received on Mon Dec 14 12:07:34 2009