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#1
03-01-2014, 08:08 PM
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Sony KV 1212
B+ from the line power supply is there but that's about it. No sound No HV No antything (well the neon light comes on but that is about it.
I assume the LV supply is from the flyback, there is voltage at the collector of the fly but nothing at the base. I have not scoped it, but I assume its not getting a drive signal. I am a little out of my comfort zone on this one as I mostly only work on old tube style sets. Any hints on where to go to trace down the problem? 
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#3
03-01-2014, 10:40 PM
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that was a wild goose chase. The ground of the chassis is connected to one side of the fly pin 10 NOT the 20v supply shown on the sams (where I get a 290 ohm reading). So the base of the horz out only sees the winding in the fly to ground, which is less than 1 ohm. So the resistance check was not good. I did pull the trans and it was fine. I did not pull the "horz conv" trans which is what drives the fly for the HV. Its kinda confusing as there is a separate trans just for the yoke.
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#5
03-01-2014, 11:35 PM
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https://www.youtube.com/watch?v=EW7q0r4sYiY
guess if I am going to work on this SS stuff and ESR meter would come in handy. Or could just use the audio tone method for a cheap alternative. Last edited by DaveWM; 03-01-2014 at 11:39 PM.
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| Audiokarma |
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#6
03-02-2014, 04:01 PM
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Quote:
Yes, an ESR meter is an excellent thing to have when working on solid-state equipment.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#7
03-03-2014, 09:22 AM
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a few other less obvious issues remained
Horz width and pin cushion pretty much did not work, I replaced a 10uf cap in the horz out circuit, took care of that. Remaining issue: if you turn down the brigntness you can cut off the screen (video or raster does not matter), all but the edges both left and right remain. its not as bad if you turn up the brightness but the edges (about 1/4" vert bands on both the right and left side) are always brighter (you can still see content with video if you have a signal, or if no signal just raster on the edges). I am guessing here that something in the brighness circuit is being effected at the horz rate (as each line is effected but the top and bottom horz is normal). As if the scan across starts out bright for 1/4 inch, then there is a bias change and it get darker (constant) until the last 1/4 inch where it get brighter again for each scan line. I am going to concentrate on that area, starting with the ABL since it seems like it would be the area that would mess up with both raster and Video content. I am guessing the blanking would only mess up on video where there is a blanking pulse (maybe not thinking that corectly have to go look at that again), so presume it should be ok. Same with video amp stages. there is a ABL transistor that gets a horz pulse from the fly, and there is a cap on the collector that looks like its function would be to filter the output from the transistor. So if the cap is open the transistor switching at the horz rate would def goof the bias up of the video out (tied to this ABL transistor).
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#10
03-03-2014, 01:37 PM
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| Audiokarma |
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#11
03-03-2014, 01:43 PM
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Watched your video and that set has a terrific picture!
Consider what other small screen portables were out there in the early 70's (cough, cough, Portacolor) of course you could have bought two or three PC's for the price of the Sony. These early Sony sets had a picture that would stand comparison to just about anything built to the end of the CRT era. I replaced a bunch of caps in my 1210 though the main problem was a bad horizontal sweep transistor. It over 40 years old, those tiny caps are probably getting pretty dry by now.
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#12
03-04-2014, 03:40 PM
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think I may have it.
scope of the collectors of the R,G, B drivers all have distortion that is not present at the base, you can see the humps on both sides of the H blanking. Base is perfect so has to be in the B+ supply to the collector. looking around there I found an open choke coil that supples the load resistors for all 3 driver transistors. I guess its getting current thru some other path to work at all, but without that choke there is a REAL nasty pulse. More late.
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#13
03-04-2014, 07:49 PM
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Got it
 it was a 4.7uf on the boost supply that powers the video output transistors. I found it while scoping the CRT back, it was on the collector but not on the base (the decrease in signal on either side of the blanking pulse. what was throwing me off was the sams did not have a boost supply HV, rather just the reg mains B+ which I had changed out. This set had a diode where a choke was supposed to be, the diode rectified pin 1 (again not on the sams) and the filter was across the boost voltage and the B+ (which seems odd since if the horz does not kick off the boost will be zero and the B+ mains will be 160, the cap is rated at 50v....hmmm maybe when that startup cap went out it took this one with it.
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#14
03-04-2014, 09:33 PM
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The fix explained
http://www.youtube.com/watch?v=hMCH6spmaXE The results http://www.youtube.com/edit?o=U&video_id=Ow7x2sRWaEU and some stills for Carmine
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#15
03-05-2014, 12:54 PM
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Quote:
Compared to the newer sets, even Sonys, the early Sony models were really complicated. 
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Linear Mode
