Old B&K 1460 'scope trace can't bring up to screen

[justkelly]

So I saw an old B&K 1460 at Goodwill and on impulse picked it up. It powers up all right, and I was able to start the initial starting procedure in the manual, but I'm having trouble vertically adjusting the trace. It's dropped down past the bottom of the CRT; I can see a glow coming from down there if I turn the intensity up, basically a vertical band of "glow".

I can adjust the band easily using horizontal adjust, but vertical adjust shows no visible change. Stability, Focus, etc no change either. When I power off the scope, I can see the trace "hop" up to roughly the center of the screen as the CRT fades, and if I turn it back on again quickly it shows up again, only to dive back down below where I can see it. So it's pushing a trace, I just can't get to it.

I had the lid off, and everything looks basically OK--no burnt-out wires or anything like that. The pot for vertical adjustment is all wired up as far as I can trace. Any suggestions as to what it might be would be welcome, as this is a nice ol' piece of kit, and I would love to get it up and running properly again. TIA!

 

[BradtheRad]

Your vertical drive plate (one or both) have a bad voltage. Probably 0V on one of them. Possibly too much on the other.

It's likely that the previous owner was unable to fix it, so he dumped it.

Can you apply a signal at high gain, and get the beam to jump up and down?

You can see a beam, and it centers on power-off. This much is good. It suggests that fixing volt levels might be sufficient to center the beam.

My old tube scope drives the plates with +-100V. Your levels may be similar. Look for test pins on the board. Normal volt readings might be printed next to them. Check these with a meter.

Or can you locate a schematic? That will be invaluable of course.

 

[E-design]

Schematic can be found here:
http://bama.edebris.com/manuals/b&k/1460/
and the manual with the circuit description,
http://radiorestorer.com/bk1460.PDF

 

[BradtheRad]

The plates are labelled 6-7-9-10 in this closeup. You need to identify the vertical plates. Trace the wires back to the sections and read which is which.



According to the schematic the plates get 110V. Once you find a faulty plate reading, it should be possible to track down at least one bad component. (More than one component might be bad.) Identifying the problem is half the battle.