HP 54645D CH A2 no response when its vertical position knob rotated

[Test Point]

Greetings all...

New guy on the forum. I ran across this forum while I was searching for any hints as to repairing the problem with the scope.

I've been an E Tech for over 35 years repairing pro-sound equipment so I'm not afraid to tear into this if I need to. I can't seem to find a "real" service manual on this yet. I'll need to contact HP/Agilent and see if I can get one.

Long story short...the place I work at was getting rid of this scope because of the problem noted in the subject line. I figured I'd check here first rather than reinvent the wheel and see if someone can point me in the right direction. The A1 channel works fine so if I need to, I can do an A-B comparison and see where the signal is going bonkers.

Thanks

[PaulAm]

There is no service manual for this scope other than "replace board ...".  Unfortunately HP never released any schematics.

I have one of these but I've never opened it up so this is just a guess.  Those things are just rotary encoders, so it could be a bad encoder, bad connection or, worst case, something on the main board.  You could open it up and swap the Ch1 and Ch2 vertical encoders and see if the problem follows.

I think the odds are good for a bad encoder but you won't know until you open it up.

[Test Point]

There is no service manual for this scope other than "replace board ...".  Unfortunately HP never released any schematics.

I have one of these but I've never opened it up so this is just a guess.  Those things are just rotary encoders, so it could be a bad encoder, bad connection or, worst case, something on the main board.  You could open it up and swap the Ch1 and Ch2 vertical encoders and see if the problem follows.

I think the odds are good for a bad encoder but you won't know until you open it up.

My thoughts too on it being the encoder. I have read that it's not hard to get to this part so I may do that this weekend. When I rotate the encoder either way, I can see the trace "trying" to move but it never moves off the X axis center line. If it turns out to be the encoder, I'm hoping that it has a manufacturer's p/n on it. If I'm lucky, it may be an off the shelf part.

[Test Point]

Well crap...I swapped out the 2nd channel encoder for the first and no cigar. It still does the same thing. Without a schematic to be able to troubleshoot this, I'm guessing this will be relegated to being a single sweep scope.  These can be had relatively cheaply so I won't put any money into it.

At the same time I was given this one, I was also given an Agilent 54622D as well that works great so that one will replace the venerable Tek 465 that has been on my bench for 20 years. The v/d contacts and the vert position pots on the 465 scope are all wonky so eventually I will tear into that and clean things up.

I do mostly audio repair so I don't need anything real fast. The 465 fit the bill perfectly for the years it was being used.