[AMRadio] SB620 experts here?

[CL in NC]

Hello all,

  I have a Heath SB620 with a scan problem I hope somebody has a solution for.  It was working just fine, and when last turned on, the trace started at the right hand side, and horiz position would not bring it back any farther than midscale. I have gone through the unit, checking the obvious, I did find a 12AT7 where a 12AU7 should have been as the horizontal amp, missed that when I overhauled it years ago, and tried a new 12AU7 with the same midscreen sweep start, and just for the heck of it, a new 12AT7, same result.  A 12AX7 gives a proper size trace, guessing due to it having the highest gain of the 12A--7 series, but to center it still requires almost all of the pot to place it correctly.  Volts, ohms, capacitors, horiz. amp plate resistors identical in value,  all good, the only thing left is the neon bulb oscillator, perhaps it is triggering too soon cutting off part of the sawtooth.  CRT potentials are correct.

Charlie, W4MEC in NC