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  #16  
Old 10-28-2015, 01:07 PM
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Kamakiri Kamakiri is offline
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Nah, not at all. You've helped me through a lot, as well as a lot of others, and I appreciate the patience you guys take to take concepts that you know, and "dumb them down"

When it comes to repair of anything, there are those who are perfectionists, those who are mechanics, and those who are just plain hacks. I'm a darn good mechanic.
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  #17  
Old 10-28-2015, 01:39 PM
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earlyfilm earlyfilm is offline
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Originally Posted by Kamakiri View Post
For me, it's difficult because I've never had any formal electronics training whatsoever . . . . . . Hands, I've got. Diagnostic skills, not so much. Doesn't stop me from trying and learning though.

One of the hardest TV repair jobs that I've ever undertaken was late 1940s TV with a stacked power supply circuit, with a humongous candohm that balanced the load between two different DC plus voltage power supplies and one DC negative voltage.

The monster candohm was open when I got the set and it was quickly located and changed out with a NOS candohm. On power-up, all three voltages were still all messed up, but in a new way. It turns out that the NOS candohm was pinched too hard in manufacture and it had a short to ground in the center.

Not hard to find, but so damned unexpected, that it was the last place I checked because I'd already changed out that bleeder network. Duh!

So, if I were you, the first thing I'd check is to verify that neither of the two resistors you replaced have a direct short to ground on either end.

The second thing I would check, would be the ohms readings on the 5V4 damper, that are in Sams. Note the '*' listing, which tells where you are to park your ground for this tube.

The final check would be to open the R123 connections to recreate the original conditions, replace the R127B, power up and see if the newest R127B gets hot. Purpose: Something else could have happened at the same time that you put in the Horiz Linearity resistor.

Since ETF also has a factory single set RCA manual for this TV, why would one use a maybe "schematic" that covers two sets that were built two years apart when the exact is available.
Sams R123 = RCA R209 and Sams R127B = RCA R232.


For the record: My nearest to formal education in electronics was the Progressive Edu-Kit in 1952:

http://www.ohio.edu/people/postr/bapix/edukit.htm

The one mentioned, along a more advanced one and with every book on electronics in the local County Library.

Hope this helps.
Jas.

Last edited by earlyfilm; 10-28-2015 at 01:55 PM. Reason: Added "For the record"
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  #18  
Old 10-28-2015, 08:52 PM
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Originally Posted by Kamakiri View Post
For me, it's difficult because I've never had any formal electronics training whatsoever. Heck, I've never even had the benefit of someone in person walking me through a set step by step. It was just something that I wanted to do ever since I was a boy, so I pick it up as I go and have been doing that for the last decade or so.
I have a degree in electronics and I took it as a trade in high school. I sometimes think that I got more useful training in high school than I did in college. I only took the first year in h.s. and I remember it being all about the math of Ohm's Law and Kirchoff's Law, the use of a Simspon ANALOG meter, and logical use of your God given senses which could be nearly as important as the former(s).

By the time I found a way to make it through college consumer electronics repair was all but done with. Even component level troubleshooting with scopes and such was reduced to nearly nothing beyond power supplies. Schools are set up to help people start careers and find jobs and that dictates the curriculm's content. Thank God that both my h.s. and college teachers were "old school" guys who were around when electronics was a true science as opposed to a digital mess of plug and play stuff called electronics. An "electronics tech" of years ago bore knowledge that makes today's "electronics tech" seem like a kindergarten student in many ways.

Just take a look at the old textbooks (which by the way we all should have) and compare to something of late. No comparison. Enough to cover what is needed to unlesah the potential graduate on industrial applications which are what most schools elaborate on these days. At least community colleges or junior colleges. I unfortunately can't say what a university electronics engineering student might go experience. Probably the equivalent of what the junior college or trade school student of the 40s or 50s experienced only up to date.

Nothing at all wrong with taking a natural interest and building on it through real world experience all while having a lot of fun. And trust me, this pool of knowledge that we all are lucky to be a part of here is used by me a lot on what often is rudimentary electronics troubleshooting. We all have strengths and weaknesses. What I love about electronics is that you never stop learing. Even with backdated technology it is a constant learning experience!
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  #19  
Old 10-29-2015, 07:22 PM
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Quote:
Originally Posted by earlyfilm View Post
So, if I were you, the first thing I'd check is to verify that neither of the two resistors you replaced have a direct short to ground on either end.

The second thing I would check, would be the ohms readings on the 5V4 damper, that are in Sams. Note the '*' listing, which tells where you are to park your ground for this tube.

The final check would be to open the R123 connections to recreate the original conditions, replace the R127B, power up and see if the newest R127B gets hot. Purpose: Something else could have happened at the same time that you put in the Horiz Linearity resistor.
Brilliant

First check: nothing has a direct short to ground.

Second check: readings on the 5V4 are dead on.

Final check: that's next.....exactly what I had planned on doing.
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  #20  
Old 10-30-2015, 04:16 PM
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Final check: that's next.....exactly what I had planned on doing.
Always do the tests first that are least likely to damage something.

Refresh my memory. Did you check your focus coil for internal resistance? If not do it before powering up the set.

Also, before you fire the set up, clip a DC voltmeter across R127B with the negative lead on the focus coil side.

As you bring your Variac up, when it hits 24 volts across R127B, the resistor is pulling 5 watts current draw and at 48 volts it is 10 watts and if you stay there more than a few moments you will fry your brand new 10 watt wirewound.
___________________________________

One never sees their own mistakes and a prime example is the final statement in my previous post:

Sam's R127B should be RCA's R185A (and not R232 which is next to it.)

James
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  #21  
Old 11-09-2015, 01:25 PM
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Welp, the set's got audio, and makes a raster. Sort of

No vertical deflection, but everything else is where it should be. I tested resistances of everything in the HV/horizontal before power up and everything is where it should be. Now, on to the vertical.

Centering control moves the line about an inch.

In retrospect, the ONLY thing I can think of was that resistor simply arcing to chassis. Might not have been enough clearance there.
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  #22  
Old 12-12-2015, 06:37 AM
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Okay, the set's operational

Turns out that the resistor WAS too close to the chassis, and it arced over. Had to end up putting a vertical blocking transformer in it as well, but everything seems fine now....except for a couple things.

The set's got inadequate width, but only by about 3/8" on either side, so I'm not so worried about that right this second. What DOES worry me is that the resistor network in the back cover is getting hot. I mean HOT. As in, I was watching the set, and I *believe* the solder on one of the resistors just melted off and POP.....the resistor dropped from the wire and I lost picture.

The contrast/AGC control also barely does anything to the picture, which is somewhat on the weak side. My other 8TS30 has full range in that department.

I don't remember any of the other 630 chassis sets I've done run so bloody hot....but then again I can't remember how much heat's back there because I've never had an issue like this.....
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  #23  
Old 12-12-2015, 10:23 AM
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Kevin Kuehn Kevin Kuehn is offline
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You need to verify your B+ voltages are what they should be at the various check points, very similar to what you just went through with the Admiral. If that resistor is burning hot, there's got to be a circuit pulling excessive current, which will show up as a lower than normal voltage at some point along the PS resistance dividing network. Voltage checks generally come first, followed by looking for circuit abnormalities causing the incorrect voltage drop.
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  #24  
Old 12-12-2015, 07:39 PM
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By the way, Kevin, I very much appreciate your patience and guidance in these sets I'm having issues with.

I've repaired or recapped 26 sets over the course of 2015. Twenty six, and that's not counting ones I've shelved with issues for the time being. But for me, restoring a TV is like having a butcher remove your appendix. He can probably do it well because he's got tons of experience with the needed tools, knows what all the parts are, and is fast and skilled with his hands. Just don't expect him to have a full understanding of what all the parts are doing.....
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  #25  
Old 12-12-2015, 10:45 PM
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No problem, Tim. I enjoy trying to help out, when I'm able, so it's a win-win situation. Have to admit I've only a handful of TV restorations to my credit, so I'm no veteran of the trade. I really Really appreciate the vast pool of knowledge that visits these forums on a daily basis. Not too many future generations will be able to experience the same honor. And quite honestly, it's a humbling experience, just being here in their presence.
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  #26  
Old 12-13-2015, 08:31 PM
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Quote:
Originally Posted by Kamakiri View Post
What DOES worry me is that the resistor network in the back cover is getting hot. I mean HOT. As in, I was watching the set, and I *believe* the solder on one of the resistors just melted off and POP.....the resistor dropped from the wire and I lost picture.
Here's where I'd start. Sams chose not to list any voltages in the power supply area, so here's Riders references for those chimney mounted resistors.

Keep in mind that those resistors with negative voltages listed are in series with the 5U4's center tap winding going to ground. Every circuit that gets B+ is drawing current through them, but in a negative direction- the higher the B+ load, the more negative those voltages will be. It's not shown in the pictorial, but there should be something in the neighborhood of neg 55v on the left terminal of R185A.


Last edited by Kevin Kuehn; 12-13-2015 at 11:54 PM.
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  #27  
Old 12-13-2015, 10:07 PM
old_coot88 old_coot88 is offline
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...It's not shown in the pictorial, but there should be something in the neighborhood of neg 55v on the left terminal of R185A.
Is R185a what's overheating?
And does R185a translate to R125 in Sams? If so, it's in parallel with the focus coil. If the focus coil were open, excessive voltage would appear across R185a, causing it to overheat.
Also the main B+ would drop some, likely causing insufficient width.
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  #28  
Old 12-13-2015, 11:29 PM
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Originally Posted by old_coot88 View Post
And does R185a translate to R125 in Sams? If so, it's in parallel with the focus coil. If the focus coil were open, excessive voltage would appear across R185a, causing it to overheat.
Also the main B+ would drop some, likely causing insufficient width.
Nope.
R185A was what I referenced from the Riders chimney wiring pictorial - it's equivalent to R127B(230 ohms) in Sams. Yeah, it's confusing as heck going back and forth between the two source materials, but I wanted to show the voltages as pictured on those resistors in Riders. The 1800 ohm resistor in parallel with the focus coil is not in the chimney. The resistors as shown in Sams that appear in the Chimney, are R127a,b and R128a,b,c. I went back and added the resistor values in red to the Riders pictorial.

Last edited by Kevin Kuehn; 12-13-2015 at 11:54 PM.
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  #29  
Old 12-13-2015, 11:51 PM
old_coot88 old_coot88 is offline
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So which resistor specifically is overheating?
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  #30  
Old 12-13-2015, 11:59 PM
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No clue. I don't think he's spilled the beans.
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