Philips L9.2EAA (yes, a CRT:) abnormal RGB amp. supply voltage

[Amdry]

G'day mates,
yes, some CRTs are still alive...well this one barely.

It's a Philips 20' L9.2E AA chassis, works perfectly but turns off after couple of minutes. Service mode shows error 12, and service manual says "Black current loop instability protection. The black current could not be stabilised. The possible cause could be a defect in one or more of the RGB amplifiers, RGB guns or RGB driving signals."

I found that supply voltage of RGB amplifier is considerably larger than it should be! 195-200V instead of 160V! I checked all resistors and capacitors around horizontal output section, but no avail. Vbatt from main supply is 95V as it should be. Some other voltages generated in HOT are elevated too.

Please comment, hope some of you still remember how to deal with these dusty buzzing big ass beasts.

[Amdry]

Re: Philips L9.2EAA (yes, a CRT abnormal RGB amp. supply voltage

Oh my, just had to adjust G2 voltage as per instructions in service manual! Buzzing big bum bugger works again!

Cheers

[stj]

Re: Philips L9.2EAA (yes, a CRT abnormal RGB amp. supply voltage

lol
philips did make good manuals for crt's

[freakaftr8]

Re: Philips L9.2EAA (yes, a CRT abnormal RGB amp. supply voltage

Is that G2 drive a potentiometer on the flyback? If so I have seen hot and cold cycles start to change the resistance on the potentiometer overtime increasing. Yes sometimes just a tweak of the G2 drive will bring things back. I remember Sony when the G2 went to high it would blank out shutting down where others would just overdrive the CRT until it started flickering and dropping out because of the cathode couldn't handle the load

Also given how much voltage a flyback has going through it and high current a lot of dust accumulates in that section and sometimes gets behind the potentiometer and starts causing it to do all sorts of crazy things

[stj]

Re: Philips L9.2EAA (yes, a CRT abnormal RGB amp. supply voltage

pot problems on philips stuff is so rare i'v not heard of it.

common on some cheap crap though, i remember a monitor from Amstrad/schneider that used to lose it's focus because of the pot.