This is a bit low on the repair list as I was given a pair of Oscilloscopes for no charge.
One is an older military type: os-245(p)u This one I was told had no vertical deflection---Brought it home and fired it up! Works fine. (so far)
The other one is a Tektronix 7704a. This thing has all the options and the gent also gave me several other of the plug in modules. (Along with a box of NOS (New Old Stock) CRT's for smaller Oscilloscopes. (Even have one CRT that is only about 1 1/4 dia. Really tiny screen) Not sure what I"ll do with them, but it is an oddity. Might toss those up on eBay or donate them to a tech school-under the "Remember what these are?" heading.
Okay, back to the problem. He let me know that the unit failed when he turned it on during a humid day. He felt it might have a carbon track that is preventing it from starting.
What it's doing: Turn it on and the neon starter flashes in the power supply and the neon starters on the high voltage board also flash rapidly and it sounds like it's arcing in several spots. I say "Sounds" like it, because I can not find any signs of arcing or carbon burnt marks. (Sorry if I kinda use older TV CRT terms--I'm decent with older CRT monitor repair. Scopes are new to me for repairing)
http://elektrotanya.com/tektronix_7704a.pdf/download.html What I could find for a service manual. Probably more to be found--but it's been a long day.
I did a full inspection didn't find any signs of brunt traces or carbon paths where high voltage could 'jump' causing issues. I did note when I pulled the high voltage lead and turned the unit on? Of course we had no picture-- But the unit seemed to fully power up and it was nice and quiet. Plug in the high voltage lead--and all the neon starters flickering rapidly--the arc sounds return (sounds like it's coming from 3 different places--power supply, high voltage board, and the CRT itself. I suspect the sound is traveling around the case a little bit and is being deceptive.
Sense the one that was supposed to not work--appears to be fully functional--I'm not in a rush to get this one working. In fact I might just put the modules up for sale on eBay or such. But as the old saying goes: In for a penny--in for a pound. I'm only out fuel for the pickup, so it's no big deal if I can't get this one up.
Any ideas would be great. I'd hate to see this one get sent to the trash heap if it's something simple.
S-