Sony 8-301W Picture Tube

[Jonathan]

I pulled my Sony 8-301W that has the B+ to ground short. Unsoldering wires and testing for shorts, I find the short is in the picture tube. I cannot tell which pin is which, but one pin is cut. The black wire on the tube socket is ground, the brown wire is B+ (13V). The resistance of the pins where the black and brown wire connect is 4 ohms. Is this the filament? 4 ohms seems low, and with the socket connected to the tube, there is a B+ to ground short of 4 ohms. This blew the original power fuse that was in there. Is the picture tube shot?

The antenna input was two pins, the tabs that connected to either the antenna or 1/8 phono jack contacted these two large pins with pressure. I was getting lots of snow despite cleaning the corrosion. The one pin was screwed into the chassis as the ground, the other one was connected to the the bypass capacitor and resistor. I removed that pin and with a drill made the hole big enough for an F connector. I screwed in the female F connector and soldered everything up. I powered it up and it blew the fuse and B+ was shorted to ground. When the drill bit finally went through the hole, the whole chassis jerked a bit. Do you think I could have caused the filament to short inside the CRT neck? The set worked before without any issues except a snowy picture. There are no VHF stations in my area, and all I ever do is use the RF output from a satellite receiver or HDTV box. Is there anything that can be done?

Thanks.

Jonathan

[Jonathan]

Bump.

Anyone know? I can't find any data on the picture tube so I'm not really sure what is wrong.

Thanks.

Jonathan

[MRX37]

The tube might be bad...

That's all I can think of.

[Eric H]

4 ohms sounds about right for the heater, the 13 volts isn't b+ but just heater voltage for the crt.
Actually 13v sounds a little high for a crt heater but i'm not familiar with the 301 so I don't know.

Probably you shorted something with the drill, look around for something out of place.

[Sandy G]

IIRC, those l'il fellers were known as Sony's "problem child" back when they were current...Altho I don't think the CRT had any "cutting edge" technology. Hate to say it, but you might have killed the CRT...Tough luck.

[drh4683]

Dont know this set at all, never worked on one. Id agree that the drilling caused the short. metal shavings fall on a filter cap that is upside down? (cap terminal lugs up when the set is in its normal position) Shavings could be shorting anything out in the vicinity of the drilled out area. Did the drill bit push something to ground when it "jerked" through and you didnt notice it happen?

[Findm-Keepm]

Just a thought...could the chassis be a hot chassis? The outer case of the "f" fitting could be in contact with a hot chassis...connect the cable....short to ground. Wouldn't be the first I'd seen. It was common for folks in the early 80's to replace the screw terminals with "F" fittings to make sets cable/Atari/MATV ready. I remember one set a customer had tried to modify for an F fitting - an RCA we never could fix - burnt runs and vaporized rectifiers in the B+.....

Just a thought, not at all familiar with the 8-301W..

Cheers,

[Jonathan]

Thanks guys, I really appreciate the replies. I think I did kill the CRT. I hate doing these stupid things and causing more damage than I Could have improved it. I checked for shavings and there were none. And I was getting B+ confused. This is a transformer set so the chassis isn't hot at all. The jerking might have damaged the CRT in some way. 13V is whats listed in the Sams, but I think it's around there used as most of the supply for the whole set. These were a problem for Sony because the vertical drive transistors had thermal runaway problems from what I've read.

Most of you guys have been working on TVs your whole lives and have lots of experience. I'm only 23, and while I learned electronics at college, I never learned tubes, and I never really repaired complex devices like TVs, especially vintage ones. Even though I might make mistakes such as causing a rare and hard to find CRT to fail, I learned for next time, so I know what to do and what not to do. I hate to learn this way, but sometimes it's the only way.

All is not lost, as on ebay these sets turn up in bad bad shape. I can get a bad one and use the CRT.

Thanks again guys for the replies. My goal is to be as good as you guys one day with all the experience you all have.

Jonathan

[andy]

Just unplug the CRT socket to see if it's causing the short. Unless you broke the glass, I doubt anything you did could have damaged the CRT. I've never seen a CRT cause a B+ short.

[jpdylon]

If you need a parts unit:
http://cgi.ebay.com/Sony-8-301W-T-V-...QQcmdZViewItem

[andy]

I would be reluctant to modify this set. They have been fetching $200-$500 on ebay if they are in good condition. They are interesting sets, but not particularly good. Mine has never provided good enough performance for daily use. The sync is very touchy, the tuner isn't very good, and I could never get rid of some slight vertical bars in the picture. This is after replacing all high ESR caps, cleaning, and adjusting.

Has anyone managed to get a good picture on one of these?

[Jonathan]

I won the auction. When I unplug the CRT socket the short goes away. Once I get the parts set I'll give that CRT a try.

Thanks again guys.

Jonathan

[Jonathan]

Well, I got the junker set, used it's CRT and I got some good progress! The audio seems to work well, and the only flaw with the picture is that it's horizontally wavy and there are white vertical stripes. What causes the waviness? I adjusted all the controls and got a decent picture out of it, just wavy, similar to a bad pincushion adjustment, and on the right side since the picture is skewed, in the middle some black sticks out, but at the right corners it's fine. Anyone know what could be wrong?

Thanks.

Jonathan