Fixing Up The Sony 5-303 - Videokarma.org TV - Video

compucat · #1 10-12-2007, 11:17 AM

A while back my little Sony broke down and I am now just getting the bug to fix it. The picture shrank on all sides and after a while the raster faded completely. The sound and tuning are ok. At first I thought the power supply was at fault. I narrowed the trouble to the sweep board.

The 300v boost supply is absent. A quick and intersting way to confirm this is look at the channel indicator light. It is a neon bulb powered from the boost voltage supply. Mine went out with the raster. After replacing caps and checking resistors, no improvement. I proceded to measure voltages in the horizontal sweep circuits. The 12.5v B+ voltage is showing up everywhere it should but there is no voltage at the base of the horizontal output transistor. Working backward from there, I narrowed it down to the horizontal oscillator transistor. Removing it from the circuit, I discovered an open between the base and emitter. It is a 2SC140. I have a junker sweep board from which I'll snag a replacement transistor and see what happens then.

This is turning out to be an interesting troubleshooting excercise, especially since the TV was previously working. After I get it going again, I'll finish recapping the sweep board. Also, I ordered a N.O.S. picture tube for it. The original was looking a little soft when it last worked.

I'll keep posting my progress for anyone who might be interested.

compucat · #2 10-15-2007, 07:02 AM

I replaced the horizontal oscillator and still no result. Upon further investigation, I found the horizontal drive transistor, another 2SC140 also to be open at the base to emitter junction. I replaced that and I now have a picture again.

The width is still not filled out all the way. I changed the horizontal output transistor and it did not improve. I thought it might be leaking. I still have to find out what's wrong with the horizontal but the set is at least working again. I really like this set and the one I have is in excellent cosmetic condition. Maybe I'll post a picture of it soon.

kx250rider · #3 10-15-2007, 01:46 PM

Quote:

Originally Posted by compucat

I ordered a N.O.S. picture tube for it. The original was looking a little soft when it last worked.

I'll keep posting my progress for anyone who might be interested.

Wow! Is that tube still available new, or did you find one NOS from a collector? The dim CRT is why I haven't bothered to recap mine.

Charles

compucat · #4 10-16-2007, 01:21 PM

Quote:

Originally Posted by kx250rider

Wow! Is that tube still available new, or did you find one NOS from a collector? The dim CRT is why I haven't bothered to recap mine.

Charles

I found a NOS tube from a company called Sphere Research. They sell many used and NOS tubes, mostly from and for test equipment.

I did get a recent quote on that tube from Video Display Corporation of $65.00 which is what I paid for the one from Sphere Research.

I have seen what the new "coupon eligible" ATSC converters are going to look like. They are about the size of the current RF modulators you find at Wal-Mart, etc. They have a channel 3 or 4 RF output so It will be easy to rig up one of these Sony's or another small set on a desktop for digital reception. At least this will make 5" TVs still useable as tabletop sets.

I do notice that the picture is somewhat keystoned at the bottom. In addition to insufficient width by about a half inch on either side, the bottom part of the raster slopes downward. News crawlers all appear to be sliding downhill instead of across. Could I have a bad yoke that is causing the width problem? Do all these sets have this geometry error?

MRX37 · #5 10-16-2007, 01:30 PM

Quote:

Originally Posted by compucat

I found a NOS tube from a company called

I do notice that the picture is somewhat keystoned at the bottom. In addition to insufficient width by about a half inch on either side, the bottom part of the raster slopes downward. News crawlers all appear to be sliding downhill instead of across. Could I have a bad yoke that is causing the width problem? Do all these sets have this geometry error?

Far as I know, the yoke controls picture rotation, color purity, and dynamic convergance. I'm not sure if it affects picture geometry or not.

Findm-Keepm · #6 10-16-2007, 07:56 PM

Quote:

Originally Posted by compucat

I found a NOS tube from a company called Sphere Research. They sell many used and NOS tubes, mostly from and for test equipment.

I did get a recent quote on that tube from Video Display Corporation of $65.00 which is what I paid for the one from Sphere Research.

May I ask, how much was shipping? [Begin Rant] I was looking for a transistor, Sphere had it, quoted me $12 for 2 (fair price), then $23 for shipping! About 10 days later, I found one up for sale on eBay - the only other bidder? Walter Shawlee, the guy that owns Sphere.... I know eBay is for everyone, but it just seemed so over the top to have some, gouge others on shipping, and then try to buy up any others out there...[End Rant]

compucat · #7 10-17-2007, 07:28 AM

Quote:

Originally Posted by Findm-Keepm

May I ask, how much was shipping? [Begin Rant] I was looking for a transistor, Sphere had it, quoted me $12 for 2 (fair price), then $23 for shipping! About 10 days later, I found one up for sale on eBay - the only other bidder? Walter Shawlee, the guy that owns Sphere.... I know eBay is for everyone, but it just seemed so over the top to have some, gouge others on shipping, and then try to buy up any others out there...[End Rant]

I believe I paid about $23 for shipping. I thought this was a bit steep considering it is only a 5 inch tube and doesn't weigh much. I accepted it because these tubes are not exactly something you can get at Radio Shack and finding one NOS is even better.

I was thrilled, however to discover that the tube came with a new 7 pin socket for it. The wires on my existing socket are getting brittle and can't handle being moved about.