Meck XB-702 restoration

[Kevin Kuehn]

Here's a set with a similar problem at about 1:00 in the first video.

https://www.youtube.com/watch?v=Ygpw87pqTz0

https://www.youtube.com/watch?v=aSEMVpJ1hzk

[Notimetolooz]

Another thing is that the problem seems to go away when you move the CRT away from the chassis.
I just had a thought.
When you look at some of the signals with the scope, like the sync, does the hum look stationary with respect to the sync pulses or does the position slowly move ?

[bandersen]

Originally Posted by Kevin Kuehn

Here's a set with a similar problem at about 1:00 in the first video.

https://www.youtube.com/watch?v=Ygpw87pqTz0

https://www.youtube.com/watch?v=aSEMVpJ1hzk

It sure does. That's a series string, floating chassis if I recall correctly.

Originally Posted by Notimetolooz

Another thing is that the problem seems to go away when you move the CRT away from the chassis.
I just had a thought.
When you look at some of the signals with the scope, like the sync, does the hum look stationary with respect to the sync pulses or does the position slowly move ?

The problem does not go away when I move the CRT away. At least not horizontally. Perhaps it's a little better vertically.

The hum moves slowly with respect to the sync. If I trigger my scope from the line, the hum locks in place.

[Notimetolooz]

Originally Posted by bandersen

The problem does not go away when I move the CRT away. At least not horizontally. Perhaps it's a little better vertically.

The hum moves slowly with respect to the sync. If I trigger my scope from the line, the hum locks in place.

Oh, I must be thinking of something else. I had a thought that if it did go away when you moved the CRT away that just maybe it was the sweep on the CRT plates that was appearing on the sync signal on the scope and the 60Hz sweep interference on the sync wasn't really the problem. However since you can lock on the line 60Hz the interference on the sync signal does come from that source.