Is this a bad CRT? 10BP4

[CJVx]

Okay, the 1M resistor is reading on spec. The HV is 8.4kV at no brightness up to usable brightness, and when the brightness is turned up all the way, presenting very pronounced retrace lines, loss of focus, and blooming, the HV measures 7.8kV. I still have the issue with the focus control, providing the best focus at the fully shorted side of the rotation.

Also, I connected the CRT filament directly to a DC power supply, and when driven at 8V, the picture did brighten some.

With any luck, this Saturday I will be picking up another one of these sets in unrestored condition. Picture tube condition Unknown, but could be interesting to see what another picture tube perspective would look like in this set.

[CJVx]

Some additions things I measured. On a variac @ 117V, I’m getting 244V at the focus coil, when it should be 215V according to the service manual. After adjusting the horizontal drive and such, I do get the sharpest image a touch above full turn to one direction. Still not sure what to make of all of this.

PS, I baked the CRT at 8.5V overnight and it has slightly improved.

[Username1]

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Usually a picture tube produces a noticeable improvement in brightness when the filament
voltage is increased, especially if the tube is getting weak. As for the HV, it's not all
that low, 1kv but you can check on a few things....

6BG6 V112 is suppose to have -115V at pin 5, is that correct? it drives the H Output
tube & gives you the HV to the picture tube.

Also at the green wire to the focus coil there should be 215V - is it correct?

And trying that spare 10bp4 when you get it is always a good idea.....


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[Username1]

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The schematic does say that at 117V source, that voltages should he within 20%, so
244v hits that..... Not sure what you should do about that..... How are all the other
voltage sources ?


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