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#76
05-31-2012, 03:07 PM
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I replaced that cap with the .0015/1KV ceramic that I had on hand, just to see what happened:
 No magical improvement in the height, unfortunately. And you're right, it changes value when heating up. After a few minutes of play, the vertical becomes unstable and then collapses. Mouser has 1KV micas of the right value. I presume those would be a better choice. Phil Nelson 
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#77
05-31-2012, 03:50 PM
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I would stick with a reg film cap. After you get the correct cap in, try reading the PP on pin 6. You need to find out why the PP is only 30v and not 140v.
I am sure you have checked, but I presume you are seeing the 275v on the red lead of the vert out. check for the 400v boost on the one side of the height (if not checked already). did not see a check mark by C3A 10uf 450v Last edited by DaveWM; 05-31-2012 at 03:55 PM.
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#78
05-31-2012, 06:43 PM
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OK, justradios has orange drops of that value. I'll order those.
Incidentally, the series-d caps I removed were .0033, not .00033, so I'm not as crazy as I thought. They were film caps and also stable, unlike the ceramic. I'll put a pair of them back in so that I can play the set for more than 2 minutes at a time while waiting for more parts to arrive. Edit: the 275V source is at 273V, like before. The 400V source was 400V when I checked before, now it is somewhat high at 430V (don't ask me why). Regards, Phil Nelson Last edited by Phil Nelson; 05-31-2012 at 08:17 PM.
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#79
05-31-2012, 07:58 PM
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Here is a Mouser .0015/1600V film capacitor:
http://www.mouser.com/ProductDetail/...71iJrRleNpY%3d I used that one or a similar value just now in my CT-100.
__________________
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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#80
05-31-2012, 08:19 PM
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Ah, under the mysterious "snubber" category. When I searched in the usual categories, everything of that value was unstocked, with 20+ week lead times. Or maybe I was too restrictive in the voltage rating. Searching their website is kind of a black art.
Phil Nelson Last edited by Phil Nelson; 05-31-2012 at 08:23 PM.
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#81
05-31-2012, 08:28 PM
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shoot, I was really hoping you had .000165 in there. I doubt the new cap will solve the problem. I know you have tried a new tube as well...
I am about out of suggestions, other than just going over your work with a fine tooth comb. Yes the snubbers are the place to find HV caps. You have tried adjusting the lin and height as they interact.
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#82
06-01-2012, 01:48 AM
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Quote:
__________________
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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#83
06-10-2012, 04:12 PM
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hmmmm, I search on predicta K5 and found a construction article, a 150k resistor is used where the sams (and you) have a 68k now. Do you have the old K5 around to check the pin 3 and 4 for resistance.
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#85
06-10-2012, 05:32 PM
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Phil what did you use on the Holiday resto? I cant see anything but the two caps and the 33k resistor, no signs of a 68k or 150k? I am assuming the same K5 is used on both models (maybe a bad assumption, dont have the sams for the holiday to compare).
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#86
06-10-2012, 08:41 PM
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The 9L37 chassis used in the Holiday and barberpole Predicta has a different vertical tube (10DE7 vs. 6DR7) and the value of that resistor in the vertical feedback couplate is different.
In that chassis, the couplate is named K4 (Sams) and the resistor is 150K. In the 10L43 chassis in this 17-inch Siesta, the couplate is K5 (Sams) and the resistor is 68K. The Sams and Philco manuals for chassis 10L43 agree on 68K for this resistor. Here's a snip of the Philco schematic, where the feedback couplate is named N2:  I've read competing theories on how to build the R3/C2 resistor/capacitor part of the vertical integrator couplate (N3 in this Philco schematic). One school says to put a .002-mfd cap on either side of a 90K resistor. That's what I did. Another school says to use two resistors equaling 90K and three capacitors equaling .004 mfd, one on each end and one in the middle, so the circuit looks more like your traditional vertical integrator. Both schools claim that their version works, so I wonder if the difference is really important. In all of the couplates that I've made, I put components on both sides of the perf board, so you won't see them all in a single photo. Regards, Phil Nelson
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#89
06-11-2012, 11:00 AM
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Quote:
Sigh. Nobody to blame but myself. I will try to find time to change it later today. I suspect this will cure the height problem. Now I see the value of testing new components when they go in. I wouldn't expect a high failure rate, but it would help prevent errors like this. Thanks, Phil Nelson
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#90
06-11-2012, 11:50 AM
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yea I know, I sure I have said it before but for folks that may have missed, this is where the value of an old school cap tester really shows up, take out the old, test its value (the null may not fully open but generally show some action), leave the settings alone, get the replacement ready and test, the eye should open without changing the settings much. Even badly shorted caps will generally still null enough to check. I sure hope this is it for you, I know its been a PITA trying to chase it down. good luck
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Linear Mode
