So near yet so far - Videokarma.org TV - Video

David Roper · #1 12-20-2008, 09:53 PM

This Hallicrafters 818 is only partially recapped, but all paper caps in the horizontal section and all electrolytics have been replaced. In the picture above it is receiving a nice strong signal at least audio wise, but the raster will not focus any sharper than what you see and even though it appears to be way off horizontal frequency, a multimeter connected to the oscillator shows the horizontal hold control varying the frequency to just below or just above spot on...yet there's no image whatsoever and what I am guessing are drive lines, but that's only a guess, i yield to the experts. What's my next step?

edsel 1023 · #2 12-21-2008, 02:20 PM

HI: change all the caps and all restistors 1 meg. and up. I just finished a T-54 and had about the samething you have now, vertical lines. replaceing the restistors brought the full picture in. some restistors were 3-5 times their orig. value.

Don Lindsly · #3 12-21-2008, 03:48 PM

Try a substitute yoke.

David Roper · #4 12-22-2008, 04:13 AM

Not a yoke, but just about everything else. The absence of any video turned out to be a heater-cathode short. Adding a separate transformer gave this result

clearly suffering from some drive problems. many adjustments and unfruitful tube substitutions later it looks like this

there are actually two narrow lines, the second is nearly invisible. There's precious little in Riders about setup of the Horizontal. So very much nearer and farther! Ideas?

David Roper · #5 01-14-2009, 02:05 PM

It's the width coil. I bought a miscellaneous collection of them on eBay (you pays your money, you takes your chances) and the least likely candidate of the bunch is the only one close to working correctly:

close enough that I might button it up with that coil and and call it good enough if I cannot locate the true and correct one.

The Hallicrafters part number is 51A1261-C. Can anybody cross that to a Stancor or other standard replacement part number?

Old1625 · #6 01-14-2009, 03:09 PM

Looks like you're closing in on it!

bgadow · #7 01-14-2009, 04:26 PM

Merit MWC-1
Stancor WC-5
Thordarson WC-20
Triad WLC-11

Unfortunatly I don't have any of them

David Roper · #8 01-14-2009, 05:08 PM

Thanks Bryan, with luck somebody does.

David Roper · #9 05-27-2009, 06:52 PM

I'd like to finally finish this one up but I still need the width coil. Thanks again to Bryan for the crosses. Anybody have one to spare?

Quote:

Merit MWC-1
Stancor WC-5
Thordarson WC-20
Triad WLC-11

jeyurkon · #10 05-27-2009, 11:41 PM

Quote:

Originally Posted by David Roper

I'd like to finally finish this one up but I still need the width coil. Thanks again to Bryan for the crosses. Anybody have one to spare?

www.oldradioparts.com has a few of these crosses listed on their site. They have a $20.00 minimum order.

John

*zenithfan1* · #11 05-29-2009, 05:53 PM

Good luck on that coil David, the set is looking good.

David Roper · #12 03-25-2011, 01:34 AM

I put this set aside for a longgg time but during that time I acquired a Merit MWC-1 width coil. When I installed it, I still had the kink in the raster. Great. But remembering that the first time I was able to get the white line to disappear was with a capacitor/resistor combination substituting for the coil, I clipped cap sub box across the coil I had just installed. After much, much more fiddling and refiddling with all of the horizontal adjustments I have this:

Perhaps not surprisingly, after the readjustment, when I remove the capacitor (.015 gives the best result) from across the coil, it reverts to a scan similarly distorted as the first picture in post #4. I guess at this point I'm soliciting opinions as to what you would do. There's obviously still something wrong (I eventually did try a substitute yoke, same results) but as long as I've found a way to make the set work, should I just stop looking and call it good? After two years I'd kind of like to get it out of the workroom more than I'd like to play sweep anomaly detective.

miniman82 · #13 03-25-2011, 01:39 AM

Looks damn good to me, I'd call it done!

Username1 · #14 03-25-2011, 05:39 AM

Picture #2 of Post 4 looks like there is only 1 picture on the screen. And the clear extra whiteness of that line makes me think its in the horiz osc. the shape of the wave is not right and the scan line is slowing down where the while vertical line is. (slower scan the beam spends more time in that spot and it ends up being brighter) Most likely its a cap discharging too quickly, same would cause the picture to be narrow. So look for a cap that is too small, changed its value - beginning to open - or a wrong part in there. Recapping without checking now and then you might have put the wrong one in there. Check the value of that coil you replaced, is it really bad? Could be the cap near or in parallel with that coil. Picture 1 of post 4 actually looks like its folded over in the middle, and again the picture looks narrow.

Phil Nelson · #15 03-25-2011, 11:50 AM

Those last images look pretty darned good to me. If the TV is stable and you can get that image quality without a lot of fiddling, I'd declare victory. Of course, this is Mr. Short Attention Span talking. Sometimes I just get bored and want to work on something different.

I had to run for my Dachis guide to see what a model 818 looks like. A cute, not-too-huge console, if that book's correct. I'd like to see a photo of the set in action when it's all put together.

Phil Nelson