TEK 465 troubleshooting

[beaug]

Tektronix 465 (S/N B276519)

I am trying to get an old Tek 465 working. I have been able to get Ch-2 working but Ch-1 will only show the trace at the very top of the display when using Beam Finder. Using the service manual, O-scope troubleshooting guide and forums I think I have isolated the problem to the Ch-1 Preamp section.

I have performed the following:

• checked DC voltage and ripple on all rails minus 2k rail all rails DC values were good. Ripple less than 4 mVAC RMS except 110V rail was 11 mV RMS (55 mVAC p-p) and had an unusual blip (see pic below). not sure if this is normal.
  
• used the Common-mode technique on TP322 and TP324. this moved the trace to the vertical center of the display (per the troubleshooting guide this indicates that the problem is in a stage prior to the Vert. Switch. section, which also tracks with the fact that CH-2 works but CH-1 does not).
• used the Common-mode technique on TP141 and TP147. This had no effect.
• checked DC values at the following test points:
       
  • TP322: +0.6135VDC
  • TP324: -0.8034VDC
  • TP326: +1.6321VDC
  • TP141: +8.529VDC
  • TP147: +7.975VDC
• re-seated the following transistors:
       
  • Q132
  • Q134
  • Q322
  • Q322

I am at a loss on how to narrow it down further. Any suggestions on what to check next?

SIDE NOTE: I can see the Trigger level as expected when pressing Beam Finder and Trigger View, but I noticed that the trigger level pot is inverted (turning it "-" raises the trigger level and vice versa) on both channels. Is this normal behavior? I am inexperienced with analog scopes.

[Paul Moir]

I can see the Trigger level as expected when pressing Beam Finder and Trigger View, but I noticed that the trigger level pot is inverted (turning it "-" raises the trigger level and vice versa) on both channels. Is this normal behavior? I am inexperienced with analog scopes.

Not really helpful but I happened to have a plugged in 465 next to me.  This is normal with DC coupling.

[med6753]

Since you have one channel working you can use it for comparison troubleshooting. Set both channel 1 and 2 to the identical setting on volts/div. Apply identical signal, such as the calibrator, to both channels. Trace the signal on both channels through the vertical circuits until you come upon a difference. That should be the area of the defect.