Tektronix analog scope issues

[1audio]

I have two vintage tek plug in scopes with similar issues.
First is a 5112 dual beam where 1 beam's vertical deflection amp is intermittent. One of the plate drivers stops amplifying and the deflection stop at the mid point.
The other is a 7403N where the horizontal deflection shrinks and then becomes a line.

I have looked at both carefully and touched up solder joints, looked for cracked traces etc. There is a mechanical aspect (tapping can get it working). The signal seems to be at the input when its not working. When probing sometimes the circuit starts working.  The 5112 circuit is quite simple. The 7403 a little more complicated. On the 5112 the failing amp acts like the connection from the emitter of Q104 to the collector of Q106 is intermittent but it checks OK with fresh solder joints. On the 5000 series the transistors are soldered in and a PITA to get out with the board mounted. Is there any history of intermittent connections inside transistors?

The 7403 has a similar problem in its horizontal amp. However everything checks OK when on the bench until it sits for a while.

I'm looking for any suggestions, ideas or ideally experiences fixing these problems.

[m k]

Have you measured from component legs?

I had once a bent leg.
It was under the body and so close that measuring it made a contact.
I found it with pure luck.
Then measured it without making a connection and the force was so little that nobody does that unintentionally.

Some been clear cracks in the middle of a joint and not something hiding in the edges but combined still so suitably that I didn't believe they are broken.

Few I've found with cold spray but that is not very easy.
Usually you believe you have found it but no, just some spray have been spilled.
Then when you really find it a drop is a night and day.

Few components I've changed since legs didn't connect anymore but those were power components and the situation was obvious.

[1audio]

I got the 7403N running reliably. I don't knok which solder joint or trace I touched up fixed it but its fixed. I had inadvertantly popped the power supply and I thought it was a lost cause but it was just the HV fuse.

The 5112 will be next and its probably a similar connection problem.