Sentinel 400-TV verticaly squashed raster

[Jonathan]

Well, I finally finished recapping my Sentinel 400TV except for the micas. It's an electrostatic set with a 7JP4. It looks like I have a good CRT. I turn it on and I get a squashed vertical lines on the screen. It's actually a bunch of scan lines squashed together. I had nothing connected to the antenna, so it should be snow on the screen, which is what it looks like, just squashed, with scanlines visible. I'm thinking a bad resistor or mica capacitor. I have another chassis and swapping tubes didn't do anything. I don't have a troubleshooting guide, and I'm afraid to go poking around under the chassis with 6kV. Is the HV working correctly? Maybe the vertical HV isn't working right?

Thanks.

Jonathan

[RetroHacker]

Originally Posted by Jonathan

Is the HV working correctly? Maybe the vertical HV isn't working right?

Hmm. I don't know - try rubbing a sock on carpet and give it a zap - see if it comes back... <grin>. Sorry, yeah, I don't know - if you've already changed the caps, I'd go back and check and make sure you've got the right values in there, sometimes it's easy to put a .1 where a .01 goes, etc. - especially if you're replacing black beauties. I've had weird problems that I couldn't find after working on the set for hours, and then I came back the next morning and noticed that I'd forgotten something simple, or mixed up a connection. It's easy to overlook things at 3AM!

Good luck.

-Ian

[sean]

You say you are getting a bunch of vertical scan lines squashed together. This sounds like your horizontal size is off. If you were seeing a bunch of horizontal lines squished together then your vertical size would be off. Either way, do either of the size controls have an effect? The scan lines you are seeing are probably retrace lines. Your set (like just about all of the 7-inch electrostatic sets of this period) does not have a retrace blanking circuit. It would just involve a couple of resistors and capacitors and you could add it to your set. I would do it after you are done with the actual restoration.

[phillipclayton]

I realize your posting is old and you may have solved your problem by now. However, I recently completed restoration on a Sentinel TV-400 and discovered an inconsistency between the chassis and the Sams Photofact for that model: the Vertical Oscillator and Vertical Amplifier tube types are reversed. Make sure the 6SL7 and 6SN7 are correctly placed with regard to the label inside the set -- not according to the Photofact. I got the backwards and it created the symptom you describe. Good luck.

Phil