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#1
12-05-2004, 02:06 AM
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Setchel-Carlson P-62
This is the kind of picture that an early Setchel barrel porable makes. It's about a model P-62. It has a 90 degree CRT but uses a silicon doubler power supply instead of the 5U4 setup used by the P-61. I was hoping this set would have a little better linearity than the 110 degree model P-66. Well, the second harmonic distortion is better, but the first harmonic distortion is pretty significant, thus the right side of the picture is squashed. This problem is still present, even after the tubes and capacitors in the H sweep sect. have been
replaced. This set has no horiizontal linearity coil, by design. Maybe that's all the better they work w/o a lin. coil? The dim little thing down below the Setchel is a Hallicrafters T-54.
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CORK 
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#2
12-06-2004, 08:06 PM
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Maybe a resistor off in the horiz osc or output area?I had one of these sets and the horiz.linearity was much better.Also did you check the resistors and caps on the yoke?BTW-nice job on the T-54 now all you need is a crt.
Last edited by tvman39; 12-06-2004 at 08:13 PM.
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#4
12-08-2004, 11:05 PM
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I checked all the comp's around the yoke, and they are of course OK. This set doesn't have any C's on the yoke winding. But I thought most of the R's and C's tacked on yokes had more to do with flyback activity, ie. trying to keep flyback yoke voltages from breaking down the yoke winding.
I don't know how bright 7JP4s are supposed to be. I have about 6 of these tubes and they are all this dim, even with 7KV on U2. For the above picture the T54 is at max brightness and the Setchel is at minimum, and the whole scene is in a dimly lighted room. Bad CRT's seems to be my undoing. I just bought another, my third, 10in RCA trying to get a good 10 tube, and this latest one has a terrible lo-emission tube. I have been trying to find a good 21in B and W 110 degree tube for a year, and no luck.
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CORK
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#5
12-09-2004, 01:18 AM
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If one of the damping resistors or caps was to change value or short on the yoke it could affect picture linearity or kill horizontal sweep all together.The 7jp4 in my vt-71 which tests good can be seen clearly in room during the daytime.The HV on my set is around 6.5 kv.The only way you could figure out how bright a new 7jp1 would be to find a NOS 7jp1 and compare it to a used one.
Last edited by tvman39; 12-09-2004 at 01:31 AM.
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#7
12-09-2004, 08:45 PM
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Cork. have you tried to play around with the value of the caps. Do it in small amounts
one at a time. might help. ed
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#8
12-09-2004, 09:30 PM
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I have an S-C portable also.
It's been recapped and works OK but it has a slight linearity problem too. There's a line in the center (from top to bottom) where the pic bunches up a little. Haven't messed with it at all to see if i could make it better. Eric
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#9
12-09-2004, 11:03 PM
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Heh. You've got a drive line!!!!
Those are fun, aren't they?  If you've got a drive control, you can turn it down to get rid of it, otherwise, I think it's from overdriving the horz output tube - check resistor values and caps around it. SCs are great sets - you've got something wrong in yours if the picture's like that...
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#10
12-09-2004, 11:11 PM
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Eric,
I don't know about this business of a compressed are in the screen center. But it seems that it might have something to do with the B+ boost. Somewhere around the center of the horizontal sweep line the yoke mag energy has all dissipated and the horizontal output tube starts to conduct again. If there were something screwed up with the B+ boost, like the boost filter cap., there would be a discontinuity in the sweep at this midmoint in the sweep. Duting the active part of the horizontal sweep there is almost a constant voltage across the yoke winding. If the B+ boost cap voltage were drooping off during the retrace and the first part of the sweep line, there would be low voltage across the yoke until the H O tube could get the capacitor back up to where it's supposed to be. On the Sam's, this capcitor is C57 for the Setchel P66, and C73 for the P-61. It's a 0.1ufd ceramic. I don't know quite how a ceramic could lose it's capacitance, but this is my best excuse for what might be going on. I suppose the damper and HO tubes could also be suspect, and of course something crazy could be going on with the HO grid drive, but ths would be really obvious with a scope. Maybe we need to trade set's problems. Your set's problem is not a designed-in problem. +
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CORK
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#11
12-10-2004, 12:47 AM
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Quote:
It wasn't real bad as I recall but I haven't run it in years. I'll try to get it going soon and take a pic. Eric
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Linear Mode
