Dove right in! Help with RCA 21-D-8628

[Electronic M]

Originally Posted by Kevin Kuehn

Although the scan lines look quite uniform top to bottom.

I couldn't see any scanlines till I zoomed in just now, but your right....maybe that lady just has a funny shaped head.

[Kevin Kuehn]

Originally Posted by Electronic M

I couldn't see any scanlines till I zoomed in just now, but your right....maybe that lady just has a funny shaped head.

If it's who I think it is she's a very tall lady.

https://www.tasteofhome.com/collecti...a-child-facts/

Julia Child was 6' 3", though she would often tell people 6' 2" (take with a grain of salt, it was quoted from a book after her passing; though she and the writer worked together) so I think that her height, camera angle, and the receiver just fudges her head a bit.

On Monday I was trying to adjust height and the vertical board sparked and probably killed a few components, and the vert osc tube. So, today I have completely disassemled the board, and I am going to replace some of the wires that have some melted insulation due to my poor soldering. I am betting that while holding my penlight and screw driver, I accidentally touched the chassis and must have made contact with the printed board area near the osc tube. I am going to check every component for resistance, capacitance, and continuity.

A thought that has annoyed me since a few weeks back has been the linearity and height pots, they are inside a shared housing to make adjustment easier. Included is a picture.
The pot on the right is from chassis B (the replacement), the left is from chassis A (the original that was in tv at pickup). When I compare resistance measurements to the printed schematic and part list, the chassis B height shows no resistance past the midpoint when turning clockwise, nor continuity between opposite ends. Chassis A's linearity reads an appropriate half-way between 1.5 meg ohms. And, chassis A's height reads correctly at half-way between 5 megohms, and continuity between opposite ends, show near 5 mohms.

I am going to assume that I was the cause of this and open the chassis B pots up to observe the layout. It is possible I could find a 5 mohm pot to replace, or is that not possible? Anyway, I am going to reassemble the entire board using a tested component per the schematic/value/etc.

Also. The serial numbers on the parts are either 8 siblings away from each other, or I don't know. The chassis numbers are further apart I think. Chassis A (original) is KCS 116C RVB 274, 74 33 L3, Chassis B (replacement) is KCS 116C 274, 74 52 L3.

Originally Posted by BandDirector

Julia Child was 6' 3", though she would often tell people 6' 2" (take with a grain of salt, it was quoted from a book after her passing; though she and the writer worked together) so I think that her height, camera angle, and the receiver just fudges her head a bit.

On Monday I was trying to adjust height and the vertical board sparked and probably killed a few components, and the vert osc tube. So, today I have completely disassemled the board, and I am going to replace some of the wires that have some melted insulation due to my poor soldering. I am betting that while holding my penlight and screw driver, I accidentally touched the chassis and must have made contact with the printed board area near the osc tube. I am going to check every component for resistance, capacitance, and continuity.

A thought that has annoyed me since a few weeks back has been the linearity and height pots, they are inside a shared housing to make adjustment easier. Included is a picture.
The pot on the right is from chassis B (the replacement), the left is from chassis A (the original that was in tv at pickup). When I compare resistance measurements to the printed schematic and part list, the chassis B height shows no resistance past the midpoint when turning clockwise, nor continuity between opposite ends. Chassis A's linearity reads an appropriate half-way between 1.5 meg ohms. And, chassis A's height reads correctly at half-way between 5 megohms, and continuity between opposite ends, show near 5 mohms.

I am going to assume that I was the cause of this and open the chassis B pots up to observe the layout. It is possible I could find a 5 mohm pot to replace, or is that not possible? Anyway, I am going to reassemble the entire board using a tested component per the schematic/value/etc.

Also. The serial numbers on the parts are either 8 siblings away from each other, or I don't know. The chassis numbers are further apart I think. Chassis A (original) is KCS 116C RVB 274, 74 33 L3, Chassis B (replacement) is KCS 116C 274, 74 52 L3.

The secon pic shows the inside of both chassis A and B's linearity and height controls. The screwdriver tip is pointing at the dead part of the resistor material, before that spot I get a reading, after (towards the right edge terminal) there is no reading.

Accidental post! But I think I killed a few caps by playing around. Extra lines, doubled screen, etc

Here is what I am talking about. The lines at the top are wider, anr the image is sort of duplicated on itself. The flicker is gone, but the horizontal has some 8-12 lines drifiting and circling the images. Sort of like a lack of horizontal hold.

[Kevin Kuehn]

Those dual pots assemblies are going to pretty difficult to source. The 137 is EIA code for manufacture CTS,followed by the date code. Apparently those were custom manufactured for RCA. It's possible the resistance elements are interchangeable with some individual printed circuit board style pots. I suppose Mark Oppat would be the guy to ask about that. https://www.oldradioparts.net/controls.html

At any rate it looks like your second set is still usable?

[QUOTE=Kevin Kuehn;3226591]Those dual pots assemblies are going to pretty difficult to source. The 137 is EIA code for manufacture CTS,followed by the date code. Apparently those were custom manufactured for RCA. It's possible the resistance elements are interchangeable with some individual printed circuit board style pots. I suppose Mark Oppat would be the guy to ask about that. https://www.oldradioparts.net/controls.html

At any rate it looks like your second set is still usable?[/QUOTE

They are, I put them in yesterday.

[DavGoodlin]

Don't bother with those if you can help it, it may have been trashed by a "tin whisker". Call Moyer Electronics, 570-286-6708 - Bill will be happy to sell you that part.

The OEM RCA parts are thier specialty, so odds are he has it. I just got two flybacks for two Philco sets there I gave up looking for long ago!

I keep taking breaks, and getting back to this point tells me that K fried some stuff last week. The grounding on the vert board wasn't secure and something popped and flashed last week. So I probably fried some of the caps, even though the caps have mostly high voltage tolerances. I probably need to pull the subassemnly for the vertical board, there are 7 different caps of varying values. Or I need to check tubes, I'll swap tubes first.

This is after tube swapping. There is a lot of buzz in the volume.

[Electronic M]

Originally Posted by BandDirector

This is after tube swapping. There is a lot of buzz in the volume.

Very sweep is running at twice frequency.

The short is more likely to have fried a resistor... Especially if you used all 630V caps and B+ is no bigger than 450V.
If you shorted the height/Lin pots you especially want to check resistors in the B± boost supply if this set uses boost to feed the vertical.
Boost is a circuit that recovers energy from the flyback and uses that energy to supply high voltage ~1000VDC to the vertical and sometimes CRT G2.

I'm 90% certain this set has a B+ boost. I tend to see the circuit lines each time I look at the schematic. I tested each resistor for it's capacity, they were all within a 10% range, some a little moreso.

What bothers me is that I keep forgetting to sit down and trace the current lines through the vertical and horizontal. Assumption tells me that the main transformer's job is to power every 'area' (vert, audio, video, horiz) at once. So, timing the travel of current through each area is the job of the caps and resistors. If something is doubled...we assume it could be a resistor?

How did you narrow to think to B+ vs. vertical or horizontal?

Here is where I see B+ boost running through vert circuitry. So checking/replacing these resistors may be a place to start?

[Electronic M]

Originally Posted by BandDirector

What bothers me is that I keep forgetting to sit down and trace the current lines through the vertical and horizontal. Assumption tells me that the main transformer's job is to power every 'area' (vert, audio, video, horiz) at once. So, timing the travel of current through each area is the job of the caps and resistors. If something is doubled...we assume it could be a resistor?

How did you narrow to think to B+ vs. vertical or horizontal?

Yes and no. If by main transformer you mean the power transformer that converts 120V from the power cord into 6.3v for the heaters and several hundred for the B+ rectifier you are not understanding a DC power supply properly.
The filter capacitors in a B+ system do not time power to different circuits. Those circuits are all getting all the power all the time.
Look at it this way...A capacitor is like a short circuit to AC but like an open circuit to DC. An inductor is like an open circuit to AC but like a short circuit to DC. Resistors behave the same to AC and DC. The filter capacitors in a B+ supply are connected between B- and B+ effectively shorting out any AC on the supply regardless of whether the AC is ripple from the rectifier or ripple from a load. (A high power load like the audio output transformer might only draws significant current (sagging the supply voltage) at peaks of the audio waveform thus the AC of the audio gets superimposed onto the B+ from loading....Or atleast it would if the filter caps weren't shorting that AC out of the B+ rail. You should not need to think about current fluctuations on the B+ rail as long as rail voltage is correct.

Film caps in vertical stages are oftentimes charged and discharged such that the voltage across them changes radically and those can control time constants... they are often wired together with tubes and resistors into something akin to an overcomplicated Japanese water pendulum resistor fills cap with charge to a certain threshold that kicks on tube to discharge cap, cap empties and tube switches off and the cycle repeats. Vertical sync essentially dumps a bunch of energy in to try and trip the tube early... vertical hold being a circuit to change the fill rate such that the circuit is close enough for the pulse energy to trip the tube but not tripping the tube before the pulse. The average vertical multivibrator circuit uses more than 1 RC circuit to get the sawtooth deflection waveform.

It's getting late and I'm starting to think I'm making things more confusing so I'll stop.