Tek 7623A - Inverted and compressed Horizontal only from TB (was 7623A + 7A26 + 7B53)

Fabio Trevisan

Hello guys,
After having purchased that of my previous topic (see subject), and initially discussed its issues, I'll separate now the topics.
Here, I focus on the rather funny behavior of the Horizontal axis... as follows:
1. It's compressed... Full sweep covers only about 3.5 divisions.
2. It moves backwards (right to left)
3. Problem doesn't affect readout (readout is correctly spanning the whole screen width and it's not inverted).

What is already checked / ruled out:
a. It's not the TB plugin... I have 2 TBs (of which, one wasn't working initially, but I found what was wrong with it), and both exhibits the same behavior, leading me to conclude that the problem is in the mainframe hor. amplifier.
b. Pressing x10 on the plugin, makes the sweep extends beyond screen, which leads to conclude that the Hor. amplifier is well capable of the output voltage span.
c. Either at x1 or at X10, the sweep is linear... (although compressed)
b. I already checked the harmonica connector P501 going into the A6 HOR. AMP. board and it's not inverted. Damn! I could bet it was it... But not!
c. I already removed and re-seated the Hor. Channel Switcher IC (U510). The socket is the dreaded Texas, but it doesn't seem there's a bad contact issue here (U510 pins are gold plated).

What has been already advised and I`m pending to check:
a. L.V. Power supply voltages and ripple. I know, that should have been my first stop.. but as soon as i opened it, I found the FAN was stuck (dried out, sticky oil) so I fixed that ahead of everything else.
b. Probing around the Horizontal Channel switcher IC (U510) and check if all voltages are present.

=> What is the nominal deflection factor of the 7000 series mainframe inputs (Diff Volt / Div. of deflection). I tried to find it on the specs, but it only says a blunt: "Compatible with all 7000 series plug-in units"
=> Is this IC 155-0022-00 a common failure?

I am posting pictures under title Tek7623a B060527...

Thanks for any advice and Rgrds,


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