GE 805 Focus Coil Question

[jr_tech]

These voltages are not correct. I read:

Pin 2, g1 .2 volt
Pin 10, g2 320 volts
Pin 11, cathode 0 to 110 volts varies with brightness control setting.

jr

[Chris K]

Originally Posted by jr_tech

These voltages are not correct. I read:

Pin 2, g1 .2 volt
Pin 10, g2 320 volts
Pin 11, cathode 0 to 110 volts varies with brightness control setting.

jr

Can I ask where you found those voltages because, as I said, the sams has voltages for the 12KP4 but not the 10BP4. Also, is that voltage for G1 0.2 volts?

[Chris K]

I'm reading directly from the Sams:
Pin 2, G1 3.1 volt
Pin 10, G2 365 volts
Pin 11, Cathode 100 volts

Like I said, this is for the 12KP4.

[Chris K]

Got the Riders service data now. Much more comprehensive.

[jr_tech]

Originally Posted by Chris K

Can I ask where you found those voltages because, as I said, the sams has voltages for the 12KP4 but not the 10BP4. Also, is that voltage for G1 0.2 volts?

I used this :

http://www.earlytelevision.org/pdf/g...sams_125-7.pdf

It may not be absolutely correct for your set, but the CRT voltages are close.

jr

[jr_tech]

Originally Posted by Chris K

The Sams gives voltages for the 12” version but I used them as a reference anyway. The cathode is supposed to be 365v DC and I’ve got 345v. G2 should be 100v and I’ve got 210v. When I was fishing to see if I could find a place to check G1, I found a 0.1uf cap connected between the lead going to the CRT and a coil had broken off of its solder tab. Of course at that moment I had to go upstairs and shut down for the night but I’m hoping that solves the issue. We’ll see. I wonder if the loss of that cap in the circuit could have led to the G2 voltage doubling?

No matter which reference you read, the cathode should not be higher than g2.

jr

[Chris K]

The Riders for the 805 chassis (also at the ETM site) has multiple versions of the TV by chassis revision and I think I found the correct specs and schematic for my chassis. It's an 805 U chassis having a cathode voltage of 340V, G1 at 110V and G2 at 25V. There is a note for the G2 voltage saying it's measured on a 50V scale (I'm assuming on a VTVM?) but that's just going to make he reading more precise on the old voltage meter correct?

[jr_tech]

Those voltages appear to be mixed up, CRT would be biased off. I would believe:

cathode 110v
g1 25v
g2 340v

would work.

[Chris K]

I must have the T or S version because this is exactly what I have. C269 is the capacitor that broke off its solder tab on the L258 coil side. Pin 10 is supposed to be 340V and I have 345V. Pin 11 is supposed to be 110V and I have 210V. Could the broken C269 capacitor solder joint account for the voltage being 100V higher on pin 11?

[Chris K]

...and you're right, I did mix up the voltage designations...that's why I'm sticking with pin # for now!!!

[jr_tech]

I would also check the caps/voltages around the brightness control. I suspect more problems than just the solder joint (should be able to vary control to get the cathode voltage closer to the g1 voltage to obtain the brightest picture ).

Also check the cap connected to the dc restorer.

jr

[Chris K]

Replaced C269

cathode 130v
g1 2.5v
g2 345v

I think I'll try the ion trap again tonight after replacing the additional caps you suggested.

[jr_tech]

Does varying the brightness control bring the cathode voltage closer to the g1 voltage?

jr

[Chris K]

Originally Posted by jr_tech

Does varying the brightness control bring the cathode voltage closer to the g1 voltage?

jr

No it does not

[Chris K]

The cathode voltage does vary from 130 to around 260 when the brightness pot is turned to the halfway position. G1 doesnt change nor does G1