Admiral 19A1, no vertical sweep (video attached)

[Kevin Kuehn]

That's strange. What's on pins 2,5,6 while you're at it? Got another 6AS5 to try?

[Kamakiri]

166 on pin 2, 164 on pin 5, 293 on pin 6. Might have one laying around here.

[Kevin Kuehn]

Better check R48,R49 too. Those two resistors bias the grid.

[Kevin Kuehn]

Pin 2,5 should be about half of whatever's on pin 6 - because the voltage on pin 6 should be basically divided in half by the 470k and 560k resistors in series going to ground. The grid(pins2-5) get's it's bias from the junction of those two resistors. Not sure why your source feeding pin 6 is so high. You might go back and measure the AC voltage on pins 4,6 of the 5Y3. Suppose to be 240vac from each pin to ground. Then 240vdc on pins 2,8.

[Kamakiri]

R48 is high....should be 560K, it's reading 704K. R49 isn't terrible, it should be 470K, testing at 496K. I should have that value here to replace.

[Kevin Kuehn]

704k isn't that far out. Basically your measured 166v is roughly half of 293v.
Better back up and measure AC volts on pins 4,6 of the 5Y3 - should be 240vac each pin to ground. Then 240vdc on pins 2,8. What's your AC line voltage?

[Kamakiri]

With the resistor changed to 550K (closest I could come), voltages dropped to exactly 152 on both pins 2 and 5. Still no changes otherwise, not that I'd have expected there to be at this point

[Kamakiri]

Originally Posted by Kevin Kuehn

704k isn't that far out. Basically your measured 166v is roughly half of 293v.
Better back up and measure AC volts on pins 4,6 of the 5Y3 - should be 240vac each pin to ground. Then 240vdc on pins 2,8. What's your AC line voltage?

Pins 4 and 6 are at 280 VAC, and 2 and 8 are at 310 VDC. Line current is 118 VAC.

[Kevin Kuehn]

That seems awfully high. Honestly I'm not familiar with how much current the HV oscillator circuit pulls from the LV supply on this set. Possibly if that's not running and producing HV, that it's making the other B+ voltages high. It's as if there's hardly any load on the LV supply.

[Kevin Kuehn]

Read back and didn't see where you measured voltage on pin 3 of the 6V6 HV osc. Sams says 3 volts, which would be 30ma across that 100 ohm cathode resistor. I suppose that's a significant part of the total load on the LV supply? Were these supply voltages always high, even when you had HV?

[Kamakiri]

I still have HV, just no sweep whatsoever. The dot in the center is horrifically bright, the only way I could get it so that it wouldn't put a nasty ion burn on the screen is to bring it way out of focus. Brightness control has zero effect on it.

[Kevin Kuehn]

Have you've checked the brightness control, and the 1M resistor coming off it's center tap? The brightness pot is fed by the same B+ on pin 6 of the 6AS5. The voltage on pin 2 of the CRT should vary from 72-180v(according to Sams) with rotation of that control. Make sure you don't accidentally measure the HV with your VOM.

[Kamakiri]

I'll get on that tomorrow morning and let you know my findings. It's 19 degrees out, and I'm pooped out from moving DuMonts in the cold that weigh as much as a conversion van

[Kamakiri]

My Sams is showing me that the 6V6 should have 3 VDC on pin 8. I've got 6.32. On pin 3, I've got 281 VDC, should be 220.

And now, seems I've lost raster......

[init4fun]

Originally Posted by Kamakiri

My Sams is showing me that the 6V6 should have 3 VDC on pin 8. I've got 6.32. On pin 3, I've got 281 VDC, should be 220.

And now, seems I've lost raster......

Tim , If this is the same set that's been kickin yer nuts with the selenium replacement and such , here's my offer ;

Next time your gonna be in eastern Mass. PM me and we can spend a couple hours going over it together . I may not be a total rocket scientist , but I did work in radio/TV repair back in the 60s and 70s (and as a special bonus I CAN even spell "rocket scientist" )