Horizontal Not Running

[vts1134]

I have a 621ts on the bench that I've recapped. The horizontal oscillator is not running so I get no high voltage. I'm hoping some one will shout out something I've overlooked. The circuit is below.



Voltages on V108
Pin 1= -154
Pin 2= 145
Pin 3= -120
Pin 4= -154
Pin 5= 50
Pin 6= -120
Pin 7= 6.2vac
Pin 8= 0

I've got 253v on the "left" side of R157 and -120v on the "bottom" side of C134.
R155, R156, R157, and R158 are all on spec and I've swapped C133. The primary and secondary on T104 both read on spec. I've swapped V108 (although only once).

Reference waveform:



Actual:



Reference waveform:



Actual:



What could I be missing?

[kf4rca]

What do you have on pins 4,5, and 6 of the horizontal discharge section?
From the waveform, it looks like your osc is running. Good because horizontal oscillator transformer is not defective.
Is the output tube v109 plate glowing red after it runs after a minute or so? What voltage do you have on pin 5 of the output tube? If not negative I'd suspect R160 has changed value.

[vts1134]

Problem solved (mistake found). The grid of my horizontal output tube was positive. I had miss-wired the connection to the +225 feed instead of -110. The horizontal is singing like a bird now.

[old_coot88]

Yeeikes! You mean the control grid (pin 5) of the 6BG6 was that much positive and the tube's still good? How long was it running in that condition?

[vts1134]

Originally Posted by old_coot88

Yeeikes! You mean the control grid (pin 5) of the 6BG6 was that much positive and the tube's still good? How long was it running in that condition?

I would say no more than 40 seconds or so at a time. I would power up the chassis, take a few measurements, then power it back down.

[old_coot88]

Glad the tube survived. I woulda thought the grid, having such a tiny thermal mass, would light up incandescent with +225V on it.