Fixing Up The Sony 5-303
 

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.

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.

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?

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.

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.