Pilot tv brightness problem

[old_coot88]

Originally Posted by timmy

It’s odd pin 1 of v9

So what is V9? Is it the CRT or something else? Any chance of posting a (hopefully legible) print of the video and CRT region?

[timmy]

Originally Posted by old_coot88

So what is V9? Is it the CRT or something else? Any chance of posting a (hopefully legible) print of the video and CRT region?

V9 is dc restore and sync tube

[jr_tech]

Sams here:

http://www.earlytelevision.org/pdf/p...sams_62-16.pdf

jr

[timmy]

Originally Posted by jr_tech

Sams here:

http://www.earlytelevision.org/pdf/p...sams_62-16.pdf

jr

Yes that’s the one and I also checked the 1n34 for laughs and it’s good. And also checked all the power supply electrolytics all good. I’m lost at this point. The resistors at the bright pot are spot on.

[old_coot88]

Hey Tim, just to cut to the chase, what are the voltages (measuring from ground) to the CRT cathode (pin 3) and G1 (pin 2)?

Since the brt. control varys the cathode voltage, what is the voltage swing lock-to lock?

Hope you're running the set on an isolation xfmr since it's a hot chassis.

[timmy]

Originally Posted by old_coot88

Hey Tim, just to cut to the chase, what are the voltages (measuring from ground) to the CRT cathode (pin 3) and G1 (pin 2)?

Since the brt. control varys the cathode voltage, what is the voltage swing lock-to lock?

Hope you're running the set on an isolation xfmr since it's a hot chassis.

Should I swing the brightness control up and down while checking these voltages or just check the voltages. And no don’t have an isolation xfmr. Lock to lock ?

[old_coot88]

Yeah, with the meter connected, just turn the control lock to lock and jot down the reading at both ends. The range can then be compared to the G1 (control grid) voltage. What you're in effect doing is varying G1 with respect to cathode, and this varys beam current (brightness) in the CRT

BTW, your meter is a digital 10 meg impedance (not an old analog VOM), right?