I just got done pulling an all night marathon working on Larry. Late yesterday I successfully replaced the one channel attenuator with the burnt out 50 ohm/1MEG switch lamp with one that works. Also cleaned the channel selection switch directly under the CRT. So now all channel indicators work properly. In order to ease the remove/install of the attenuator assembly I removed the PSU/X-Axis board. That's when the project took 2 giant steps backward. Upon re-install of the PSU board I now had half a blob for a trace. Similar to the original fixed intensity issue but this time I could vary the intensity. When I rotated the chassis to check things I heard a jingle of something moving around right in the vicinity of the CRT. Uh-oh. Checked again and confirmed coming from the CRT.....or at least I thought it was. Decided to pull the CRT.
Replacing the CRT is not difficult but re-installing the vertical deflection plate wires is a real challenge. The horizontal is a piece of cake. Anyway, it did NOT fix the screen blob. And shaking the CRT revealed no rattle. BUT....I'm glad I changed it. Look at the silicone where the HV enters. All yellowed and appears to be arcing in the past. I've never seen one yellow like this and the replacement wasn't. I think I avoided a future issue.
Anyway, after installing the replacement CRT the rattle went away but still had the blob. So I pulled the PSU board and checked for issues. Found nothing. Decided to install the old PSU board. Turned the chassis on it's side and heard something hit the bench. A transistor.
![WTF? :wtf:](https://www.eevblog.com/forum/Smileys/default/wtf2.gif)
After searching around I found it's home on the sweep board. In the pix it's the one directly in front of that orange disc cap. In the mean time I had installed the old PSU board. Now had a good trace. Pulled the transistor to confirm and got a blob. So pulled the old PSU board and installed the new one. Good trace.
![Phew :phew:](https://www.eevblog.com/forum/Smileys/default/phew.gif)
![](https://imagizer.imageshack.com/v2/xq90/922/ujDO30.jpg)
So net result is now I'm ahead of where I was yesterday, although it took all night to get there.
![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
As long as I don't run into any other unexpected issues here's what is left to do:
Check CRT bias. I think it's set too high.
Still have to figure out the B sweep knob sync with the A sweep.
Compensation and calibration (There's that dirty word again but that's what Tektronix calls it)
Performance check.
Burn-in.
![](https://imagizer.imageshack.com/v2/xq90/924/k4LFm4.jpg)
I think I'm gonna go get some sleep.
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)