Found this RCA model 21-CT-7857 from 1956 at an estate sale. Perched up on the 3rd shelf about 7 feet off the ground!

https://live.staticflickr.com/65535/54291956464_e617403cdf_c.jpg (https://flic.kr/p/2qHAt9U)
Getting it down was an interesting challenge!

https://live.staticflickr.com/65535/54289294310_88aed763bb_c.jpg (https://flic.kr/p/2qHmPMG)

Big thanks to Doug for helping out
https://live.staticflickr.com/65535/54292150790_0624fdaa30_c.jpg (https://flic.kr/p/2qHBsVm)

Safe and sound back at my place. Also, grabbed a blonde Zenith porthole.
https://live.staticflickr.com/65535/54289102819_3fecac5792_c.jpg (https://flic.kr/p/2qHkQS8)

Looked around but could not find the legs.

https://live.staticflickr.com/65535/54288864551_b2635edaa9_c.jpg (https://flic.kr/p/2qHjC34)

First peek inside. The 21AXP22 is a replacement and dated mid 1963.
https://live.staticflickr.com/65535/54288079612_eb9cdc64f0_c.jpg (https://flic.kr/p/2qHfAGC)

Just tested the CRT and am happy to say it tests like new! Excellent emissions on all guns and needle does not budge under life test.

https://live.staticflickr.com/65535/54291720426_3ea8987729_c.jpg (https://flic.kr/p/2qHzfZh)

Shiny getter.
https://live.staticflickr.com/65535/54290837857_088059f5dc_c.jpg (https://flic.kr/p/2qHuJCz)

https://live.staticflickr.com/65535/54291720416_4184530569_c.jpg (https://flic.kr/p/2qHzfZ7)

Peek inside the HV box.
https://live.staticflickr.com/65535/54291720401_6223bc633b_c.jpg (https://flic.kr/p/2qHzfYR)

Won't be getting to it for a while, but it looks very promising

Congratulations. It should be interesting as you work through the set. This model is in Elvis Presley’s piano room at Graceland.

Is that radio console next to it a Capehart turnover changer console?

No idea - I couldn't reach it

We have legs. Found some NOS on eBay. Not quite the same as the originals, but they'll do.
A small step in the project, but it's sure nice to get off the ground.
https://live.staticflickr.com/65535/54392280997_6da795bbcc_c.jpg (https://flic.kr/p/2qSsE9e)

Finally got this set inside with a little help.
https://live.staticflickr.com/65535/54884288856_24b302a7a5_c.jpg (https://flic.kr/p/2rBWjWm)

https://live.staticflickr.com/65535/54888947965_24a3306914_c.jpg (https://flic.kr/p/2rCmcVP)

Chassis is filthy but all there. I only spotted two old repairs done from the topside.
https://live.staticflickr.com/65535/54884509268_1b46fa98f5_c.jpg (https://flic.kr/p/2rBXssy)

The circuit board are wire-wrapped (with some soldered) on the underside and cannot be easily removed.

So, I'll do my best to work on them in place with this massive chassis up on the workbench.

https://live.staticflickr.com/65535/54884575515_73a523c12e_c.jpg (https://flic.kr/p/2rBXN9K)

Did a few clean test spots to see what I'm dealing with.
https://live.staticflickr.com/65535/54892906003_bd01075d8d_c.jpg (https://flic.kr/p/2rCGuvR)

The boards are so dirty I'm having trouble reading the component values and resistor stripes.
https://live.staticflickr.com/65535/54892684716_58e262d697_c.jpg (https://flic.kr/p/2rCFmJy)

So, I will try unmounting the boards. The unwrapping tool I use on Predictas also works with this set.
https://live.staticflickr.com/65535/54892913848_ebe285e3a6_c.jpg (https://flic.kr/p/2rCGwR7)

Looks like RCA decided to save a few pennies and used a metal can crystal.
https://live.staticflickr.com/65535/54897377146_1de3c86520_c.jpg (https://flic.kr/p/2rD6pCw)

https://live.staticflickr.com/65535/54897621609_a3338e39ed_c.jpg (https://flic.kr/p/2rD7Eip)

I have a few glass types I've saved over the years. Ah, that's better.
https://live.staticflickr.com/65535/54897377141_c531889e37_c.jpg (https://flic.kr/p/2rD6pCr)

My CTC-7s and I believe my CTC-9s used glass crystals...Since it's socketed on the 5 it may have been replaced before. It's not uncommon for the crystal to fail on sets of this vintage.

Looks like RCA decided to save a few pennies and used a metal can crystal.
https://live.staticflickr.com/65535/54897377146_1de3c86520_c.jpg (https://flic.kr/p/2rD6pCw)

https://live.staticflickr.com/65535/54897621609_a3338e39ed_c.jpg (https://flic.kr/p/2rD7Eip)

I have a few glass types I've saved over the years. Ah, that's better.
https://live.staticflickr.com/65535/54897377141_c531889e37_c.jpg (https://flic.kr/p/2rD6pCr)

I can't quite make it out...those metal crystals are stamped with their production date. Maybe '68? I think I've only had one set pass through my hands that still had glass.

3-56 and very likely original to the set. It's had very little servicing and all the tubes appear to be RCA branded

Lots of oddball values in this set like 0.0027 @ 1,600 volts. So I'll have to place an order before I can do much more.
https://live.staticflickr.com/65535/54899304329_6b73ec8415_c.jpg (https://flic.kr/p/2rDghvP)

Cleaning certainly helps. Just warm water and Simple Green. Some residual wax remains from the old caps but I'm just going to leave it.
https://live.staticflickr.com/65535/54898222657_3873cb7584_c.jpg (https://flic.kr/p/2rDaJYi)

Chassis is another matter. I'm using CLR to remove the rust and cadmium sulfide/oxide.
https://live.staticflickr.com/65535/54899374475_26b8f1016f_c.jpg (https://flic.kr/p/2rDgDne)

https://live.staticflickr.com/65535/54899068931_360ab7e66e_c.jpg (https://flic.kr/p/2rDf5xe)

1600V isn't super common but most color and some monochrome have one or 2 caps at 1k, 1600V, or 2kv. I used to stock a full spectrum of 630V and have a separate bin for 1-2KV caps, but lately on the the Panasonic red ceramic covered film caps I favor 1.6KV long leads have been cheaper than 630v if 630V is even still available....so much of my 630 stock has moved to being 1600v.
Stuff not from the 40s especially RCA some power of 10 x 27 is common. I typically stock .1, .12, .15, .22, .27, .33, .39, .47, .56, .68, .82 and 10x and 100x lower capacitance in film.
...gives me just about all capacitance values in the modern value system used in sets 1975 and older and better matches for the prewar system...some values rarely get used but that just means I only need 10 to restock every 3rd to 5th restock order.



Lots of oddball values in this set like 0.0027 @ 1,600 volts. So I'll have to place an order before I can do much more.
https://live.staticflickr.com/65535/54899304329_6b73ec8415_c.jpg (https://flic.kr/p/2rDghvP)

Cleaning certainly helps. Just warm water and Simple Green. Some residual wax remains from the old caps but I'm just going to leave it.
https://live.staticflickr.com/65535/54898222657_3873cb7584_c.jpg (https://flic.kr/p/2rDaJYi)

Chassis is another matter. I'm using CLR to remove the rust and cadmium sulfide/oxide.
https://live.staticflickr.com/65535/54899374475_26b8f1016f_c.jpg (https://flic.kr/p/2rDgDne)

https://live.staticflickr.com/65535/54899068931_360ab7e66e_c.jpg (https://flic.kr/p/2rDf5xe)

https://www.youtube.com/watch?v=GuAXcZmLNmM

After recapping mine, I couldn't get the HV to run. Horizontal frequency wouldn't go quite high enough. I finally figured out that I had put one end of a cap on the horizontal board through an extra hole...a hole that went to ground.

Im working on my Philco CTC11 clone, it has a tube crystal like that.

Last chassis to use them, both my CTC12s have a can.

Progress update. Horizontal and vertical board done. Moving on to the sound.
https://live.staticflickr.com/65535/54908164225_6381a04078_c.jpg (https://flic.kr/p/2rE3GfD)

https://live.staticflickr.com/65535/54908164230_46ab5d1d7e_c.jpg (https://flic.kr/p/2rE3GfJ)

Also took a closer look inside the HV box. Amazingly all the tubes appear to be original.
That includes the early 6BK4 shunt regular design with no integral x-ray shielding.
https://live.staticflickr.com/65535/54908075578_843d3443a3_c.jpg (https://flic.kr/p/2rE3eUf)

https://live.staticflickr.com/65535/54908102429_3ab199e385_c.jpg (https://flic.kr/p/2rE3nTc)

Wow, the original 6BK4 shows no signs of browning from x-rays. Seems to confirm this is a low hour set.
https://live.staticflickr.com/65535/54907918216_a52e877a15_c.jpg (https://flic.kr/p/2rE2r87)

Here are some heavily used ones for comparison.
https://live.staticflickr.com/65535/54908233900_4642e09da7_c.jpg (https://flic.kr/p/2rE43XW)

Kind of Mouser to take such good care of this lone capacitor.
https://live.staticflickr.com/65535/54909064627_fe8e404cb9_c.jpg (https://flic.kr/p/2rE8iUP)

I'll work on the chroma and IF boards in place next then move on to the chassis mounted components.
https://live.staticflickr.com/65535/54910248350_09c614a368_c.jpg (https://flic.kr/p/2rEenMQ)

Kind of Mouser to take such good care of this lone capacitor.
https://live.staticflickr.com/65535/54909064627_fe8e404cb9_c.jpg (https://flic.kr/p/2rE8iUP)

I'll work on the chroma and IF boards in place next then move on to the chassis mounted components.
https://live.staticflickr.com/65535/54910248350_09c614a368_c.jpg (https://flic.kr/p/2rEenMQ)


I think mouser has some kind of code on how to pack something based on how many there are. I'll order a bunch of different film caps and sometimes they'll be in the price break order of 10, sometimes I'll order 12, sometimes I'll order 100 ....If they come in 100 from Panasonic I'll get a Panasonic bulk bag, on qty 10 I'll get a normal mouser ziplock, on qty 12 they'll fold the ziplock funny and staple it or tape the end shut or some other goofy nonsense that makes the ziplock harder to reuse (which I usually do). I've seen different methods used for different odd number parts in an order too so I think it's some kind of nemonic used by the packers to check themselves...

So I'm chiming in to ask a question . ONCE restored are these Ctc5 somewhat reliable. I had a ctc4 a while ago and the color sync circuit kept failing restored. I asked the te h if they can improve the circuit with better restore and or caps. Fixed set and didn't respond on any possible upgrades tried on circuit. Ran set once in a while and same circuit failed. Just got rid of it since not a reliable watcher.

DOES anyone do any engineering or reliability upgrades to improve run times in hours of these sets. Those sockets look pretty crispy.

If I was ever to get an old color tv, ways to maximize uptime in hours running. If I had that set, I would readily change out those plastic sockets for ceramic. These sets produce tons of heat. Does anyone run their old tvs with cooling fans ??

I guess those sockets look OK, might be pict HV tube got toasted..

I've never owned a working example before, but I've heard from others they are finicky. The convergence is difficult and potentially needs to be done every time you move the set around due to the Earth's magnetic field.

Cleaning up beautifully
https://live.staticflickr.com/65535/54910594208_a7f8c5d80e_c.jpg (https://flic.kr/p/2rEg9AU)

Also started digging into the flyback area.
https://live.staticflickr.com/65535/54912648240_de68dc0d73_c.jpg (https://flic.kr/p/2rErFcf)


I wonder if this is what took the set out of service? All tubes are RCA branded and many are originals.
https://live.staticflickr.com/65535/54912593604_63ee20f05d_c.jpg (https://flic.kr/p/2rEroXf)

Found an old service tag
https://live.staticflickr.com/65535/54912345261_91f3058640_c.jpg (https://flic.kr/p/2rEq88t)

https://live.staticflickr.com/65535/54911476537_b95ac95297_c.jpg (https://flic.kr/p/2rEkETt)

https://live.staticflickr.com/65535/54911476527_0dcaeae74c_c.jpg (https://flic.kr/p/2rEkETi)

So I'm chiming in to ask a question . ONCE restored are these Ctc5 somewhat reliable. I had a ctc4 a while ago and the color sync circuit kept failing restored. I asked the te h if they can improve the circuit with better restore and or caps. Fixed set and didn't respond on any possible upgrades tried on circuit. Ran set once in a while and same circuit failed. Just got rid of it since not a reliable watcher.

DOES anyone do any engineering or reliability upgrades to improve run times in hours of these sets. Those sockets look pretty crispy.

If I was ever to get an old color tv, ways to maximize uptime in hours running. If I had that set, I would readily change out those plastic sockets for ceramic. These sets produce tins of heat. Does anyone run their old tvs with cooling fans ??

I guess those sockets look OK, might be pick HV tube got toasted..

As someone who has owned and fixed every RCA roundy color chassis (except the CTC-12) I can tell you that if you want a reliable regular use set shoot for a CTC-7 or later. The CTC-7 was RCAs first chassis to use the modern convergence and chroma demodulator circuits that they stuck with until the end of roundys. The CTC-5 and earlier they were experimenting with different circuits because what they had was either too expensive or not sufficient in performance...the CT-100/21CT55 was on the expensive end, the CTC-5 was on the insufficient performance end (they cost reduced it so bad they backtracked on the CTC-7). If you have your heart dead set on something older than the CTC-7 my recommendation would be the 21CT55... It's basically a CT-100 factory modified to drive a 21" CRT (and you can make any 21" roundy color work with minimal tweaks to the set) so it has the engineered for best possible quality model 5 NTSC committee demonstration chassis that sold the FCC on all electronic color. I run my 21CT55 somewhere between daily and monthly and have done so for over 5 years now with minimal maintenance....the downside of the 21CT55 is rarity (there's around 40 in existence) and expense...I paid nearly 2k for my set in unrestored barn find condition, and they use a TON of caps including needing the expensive doorknob HV caps changed (I've worked on 2 of these chassis and both either came to me with shorted doorknobs or developed them after some use), and the general complexity of the chassis makes for More general parts replacement than most.

More progress in the HV area
https://live.staticflickr.com/65535/54921813910_8e0e4b130c_c.jpg (https://flic.kr/p/2rFfDQ3)

It sure looks like this is a crude old replacement.
That added 56K resistor leads me to believe the pot is not quite the right value. Will investigate further.
https://live.staticflickr.com/65535/54921718543_6d90b1fa46_c.jpg (https://flic.kr/p/2rFfatM)

https://live.staticflickr.com/65535/54921813905_b6712d3c89_c.jpg (https://flic.kr/p/2rFfDPX)

I was able to remove the HV box rust while preserving the labels. I then clear coated with poly.
https://live.staticflickr.com/65535/54921803459_02e681133c_c.jpg (https://flic.kr/p/2rFfAHR)

https://live.staticflickr.com/65535/54921859310_4e15f1dc9c_c.jpg (https://flic.kr/p/2rFfTjN)

https://live.staticflickr.com/65535/54920641137_14c1f7d680_c.jpg (https://flic.kr/p/2rF9DcP)

The focus control should be 200K rated for 1W.
There's an Allen Bradlay 2W mil spec Type J pot in there. The resistor is not original.

The pot next to it is horizontal centering while the 3-pos switch is width.

https://live.staticflickr.com/65535/54921968291_8437b87f30_c.jpg (https://flic.kr/p/2rFgrHM)

I can't make out a value. I think that's a part# stamped on it. Seems to measure about 150K across.
https://live.staticflickr.com/65535/54921999176_864bbf4512_c.jpg (https://flic.kr/p/2rFgAUh)

Boy they sure did tinker with this design.
https://live.staticflickr.com/65535/54922274780_561c9bf2c9_c.jpg (https://flic.kr/p/2rFi1Q5)

How often do you see a resistor with a violet multiplier?
This 100M resistor sets the bias on the 6BK4 HV regulator tube.
None of my meters go that high directly, but I can put my Fluke 27 in nano Siemens (conductance) mode where 1nS = 1,000M.
This allows measurements up to 100,000M ohms and it is off as are the associated 1.8 M resistors.
https://live.staticflickr.com/65535/54923619074_9cda0935ce_c.jpg (https://flic.kr/p/2rFpUry)

Luckily, 100M resistors are still readily available.

Now, this is a simplification of the HV circuits used in the chassis that came before and after. They used fixed resistors in place of a HV control.
It's been recommended by EM that the circuit be modified and a control installed like the ctc-7 chassis.
That's detailed in this thread. I will do that once (if) I get this set actually working.
https://antiqueradios.com/forums/viewtopic.php?t=425833

https://live.staticflickr.com/65535/54923370191_797124557c_c.jpg (https://flic.kr/p/2rFoCst)

Wow. Makes me wonder what kind of material the original 100 M was made of.

Here's a good article from Sylvania on the shunt regulator: https://www.worldradiohistory.com/Archive-Company-Publications/SYLVANIA%20NEWS/Sylvania-News-1967.pdf

I see now how it works. It's not so much a fixed voltage regulation set to a reference as it is a constant voltage regulation by load balancing between the shunt regulator and CRT beam current.

That variable control sets the operating point. I've heard from a number of owners that these CTC5s suffer from low HV and adding an adjustment helps.

Not much to do on the IF board. Note the germanium detector diode in the lower right.
https://live.staticflickr.com/65535/54922506297_35712061f3_c.jpg (https://flic.kr/p/2rFjcDK)

I wasn't going to remove this board, but it was just too darn dirty.
It has a delay line and funky three-legged part on the underside.
https://live.staticflickr.com/65535/54924589424_e8b853b60c_c.jpg (https://flic.kr/p/2rFuSTJ)

https://live.staticflickr.com/65535/54924539023_7ae59a9989_c.jpg (https://flic.kr/p/2rFuBUK)

Great pics banderson. Electro M Great info! Your knowledge is extensive. I'm glad to see some upgrading to some solid state parts. While not being a purists. More uptime views than on bench makes these more feasible.

It's ironic your signature Electro M. I had a 25mc33 or something similar zenith rounds. Didn't keep but should of. Cabinet was good old fashioned particle board. But the tv was a great performer and nice picture.
Have not seen another zenith roundy near me since.

One board left (chroma demodulator) plus some parts under the chassis.
https://live.staticflickr.com/65535/54926588289_50f5b1fb55_c.jpg (https://flic.kr/p/2rFF85V)

Bring on the x-rays ⚡
https://live.staticflickr.com/65535/54926340156_bcf9da055f_c.jpg (https://flic.kr/p/2rFDRjL)

Looking good , but the chassis will outlast the crt it would be nice if someone or some company would start rebuilding crts. I speak for all vintage tvs b&w and color. Got to see the first picture from that set.

Chroma demodulator board is being worked on next. I'm going to be extra careful with this one due to all the transformers and coils.
https://live.staticflickr.com/65535/54928828791_60834c97ae_c.jpg (https://flic.kr/p/2rFSB7g)

I also tested all the tubes. It seems that those with white printing are originals while the red are replacements.
About 1/2 of the tubes appear to be originals and five of those were weak or dead. Two of the red were also weak.
https://live.staticflickr.com/65535/54929072054_650e677b05_c.jpg (https://flic.kr/p/2rFTRqs)

Nice work, is that chroma board kinda toasty or just dirty?.
I would like to find another color roundy any high heat tubes definitely would swap out to ceramic sockets. It's a shame no tv shops thought about this if customers were willing to keep their sets long term.

I count about 22 potentiometers and 7 adjustable coils along the front of the chassis. Most are for dynamic convergence I believe.
This should be fun!
https://live.staticflickr.com/65535/54938457480_4b4c6cf026_c.jpg (https://flic.kr/p/2rGHXo9)

https://live.staticflickr.com/65535/54938457470_9062065a59_c.jpg (https://flic.kr/p/2rGHXnY)

On my CTC5, the static convergence pots had a crack at the tap in the carbon track. I think Wayne had the same on his CTC5.

My solution was to visit an auto parts store and buy a can of conductive paint used for fixing car rear window heating element traces.

I applied the paint at where the pot element tapcrack was and after 12 years it is still working fine.

Thanks for the tip. After cleaning with DeOxit F5, some of them still sound crusty when rotated.

I havent seen this view of the chassis in years!This brings back memories of my first convergence attempt with this chassis.I was 12 years old and with some advice from the tv shop I hung out at,I got it reasonably good!A few years later,one of the convergence pots failed and I bought a replacement. Still have the new pot.Have not installed it yet. RonL

I just remembered what the failed convergence pot was for. blue lateral adjustment.my chassis has a electro magnet on the Crt neck for that function.it took me a few years to find the service info with that coil included.Does your chassis have a permanent magnet on the Crt neck for blue lateral adjustment? It looks like you have a blue lateral adjustment pot so that would mean you have a blue lateral.electromagnet as well?RonL

I just remembered what the failed convergence pot was for. blue lateral adjustment.my chassis has a electro magnet on the Crt neck for that function.it took me a few years to find the service info with that coil included.Does your chassis have a permanent magnet on the Crt neck for blue lateral adjustment? It looks like you have a blue lateral adjustment pot so that would mean you have a blue lateral.electromagnet as well?RonL

I've had 2 table model CTC-5 sets. One with electromagnetic blue lateral, the other with permanent magnet blue lateral. The one with permanent magnet lateral had a IIRC screen pot in the location that the electromagnetic lateral set had the lateral pot.

I finally wrapped up work on the chassis and replaced a few bad tubes.
https://live.staticflickr.com/65535/55009293840_eb02035386_c.jpg (https://flic.kr/p/2rNZ1yG)

https://live.staticflickr.com/65535/55009293835_3d897cae34_c.jpg (https://flic.kr/p/2rNZ1yB)

I used all RCA branded tubes.
https://live.staticflickr.com/65535/55009293830_60b6229f94_c.jpg (https://flic.kr/p/2rNZ1yw)

I quickly noted a few tubes were not lighting up. One of the 5U4s died and a couple of the PCBs were not making good ground contact.

Once that was sorted out, I was able to receive clear audio through the tuner.
https://live.staticflickr.com/65535/55009160393_828be2de58_c.jpg (https://flic.kr/p/2rNYjTT)

Time to put it in the cabinet and makes some x-rays.
That gizmo on the right side monitors the horizontal output tube current.
https://live.staticflickr.com/65535/55009293785_32f8d13ba8_c.jpg (https://flic.kr/p/2rNZ1xK)

I was first treated to a pulsating out of focus image and some high pitched ringing.
https://live.staticflickr.com/65535/55009160343_cb7dd1c5f2_c.jpg (https://flic.kr/p/2rNYjT2)

I realized this set was really loading down my variac and turned it up to get about 117 going in.
Image got brighter and more focused. HOT current at about 150mA
https://live.staticflickr.com/65535/55009248564_86a1d97353_c.jpg (https://flic.kr/p/2rNYM75)

Feeding a color bar test pattern resulted in this. Hor. frequency was way off.
https://live.staticflickr.com/65535/55009160353_ac99f2005a_c.jpg (https://flic.kr/p/2rNYjTc)

Needed to go about 7 full rotations on the hor. frequency control.
Set is much happier now. No more ringing and the image is sharper.
https://live.staticflickr.com/65535/55009248594_d679b98f6e_c.jpg (https://flic.kr/p/2rNYM7A)

Convergence needs a bit of work ��
https://live.staticflickr.com/65535/55009248609_d8d64425b2_c.jpg (https://flic.kr/p/2rNYM7R)

Adjusted the DC bias and screen settings by eye for a big improvement
https://live.staticflickr.com/65535/55010719899_3d9ac7eef5_c.jpg (https://flic.kr/p/2rP7jtV)

and then I tried adjusting the vertical centering, heard a pop and it's dead :shock:
I hear it's likely to be tin whiskers and the main fuse popped.
https://live.staticflickr.com/65535/55010634593_20a2eb2fb2_c.jpg (https://flic.kr/p/2rP6T88)

This is the vertical centering control I touched when the set died.
https://live.staticflickr.com/65535/55020229200_7030639a35_c.jpg (https://flic.kr/p/2rPX4go)

No tin whiskers visible inside, but I did get erratic readings when I rotate while measuring resistance. Some DeOxit seems to have taken care of it.

https://live.staticflickr.com/65535/55020174939_4ac7f98dd5_c.jpg (https://flic.kr/p/2rPWM8R)

It was F103 - a 3/4 amp fuse that popped.
I had to order some Littlefuse N-3/4 type fuses.
Meanwhile, I replaced the original 1V2 and 3A3 tubes with NOS.
We will resume when the fuses arrive.
https://live.staticflickr.com/65535/55020229195_f42ee9d9e4_c.jpg (https://flic.kr/p/2rPX4gi)

Damn. Should have ordered short 'C' types, not 'N' types.
https://live.staticflickr.com/65535/55034872269_2595bdb015_c.jpg (https://flic.kr/p/2rRf796)

Meanwhile, I went hunting and found the missing brightness knob.
https://live.staticflickr.com/65535/55034610996_27a6634f5d_c.jpg (https://flic.kr/p/2rRdLto)

https://live.staticflickr.com/65535/55034954735_235fcbe0a8_c.jpg (https://flic.kr/p/2rRfwDV)

Will have to wait another week for the right fuses.
https://live.staticflickr.com/65535/55033707247_d16d648caa_c.jpg (https://flic.kr/p/2rR98Pv)

Pooch looks as disappointed as you are:(

Proper fuses arrived today. I'll give them a try tomorrow night.
https://live.staticflickr.com/65535/55038739378_01b11beac9_c.jpg (https://flic.kr/p/2rRzVGo)

We are back in business!


I did some more adjustments by eye and it's better but it's time to go through it methodically from start to finish.
However, I think I should replace the original 3A3 HV rectifier and HO tube before that. I say that because I'm having trouble filling the width and the image blooms/loses focus if I don't set the brightness and contrast just right.

Even so, it is watchable.
https://live.staticflickr.com/65535/55040593174_50ae8741a7_c.jpg (https://flic.kr/p/2rRKqLo)

https://live.staticflickr.com/65535/55039432772_0bdcca1289_c.jpg (https://flic.kr/p/2rRDtPs)

https://live.staticflickr.com/65535/55040593149_ae385a636a_c.jpg (https://flic.kr/p/2rRKqKX)

https://live.staticflickr.com/65535/55040674125_96ed3df607_c.jpg (https://flic.kr/p/2rRKQQ6)

One thing that's worth doing both for blooming and improved HV is to convert it to the CTC-7 HV regulator circuit. The only difference is one of the CTC-5 fixed resistors was replaced with a pot and a fixed resistor on the CTC-7. This allows you to adjust the HV regulator as all previous and subsequent RCA color sets did. Setting it so it just starts to limit at the max HV spec on the schematic is usually a noticeable improvement over what fixed resistors and whatever emissions of the tube has presently arbitrarily achieve.

Yes, I do plan on making that mod - thanks for the reminder.

I'm slowly improving the convergence and color hues, but a new problem has cropped up.
https://live.staticflickr.com/65535/55043477032_a508736c6e_c.jpg (https://flic.kr/p/2rS1d35)

After running about 10 minutes, I get a dark band, then the image fades out, then the screen goes dark.
A few seconds later, it comes back fine for a minute or so, then the cycle repeats.
Probably temperature related, just seems odd that it recovers so quickly. Not much time for anything to cool down.
Not sure yet if the problem lies in the HV supply or the video drive.
Here's a short video showing the problem.
https://youtube.com/shorts/ODEe6L3QyIY?feature=share

https://live.staticflickr.com/65535/55044713030_9d1748f9d0_c.jpg (https://flic.kr/p/2rS7xso)

https://live.staticflickr.com/65535/55044555668_fe25a19e8b_c.jpg (https://flic.kr/p/2rS6JFf)

Rather annoying as it's playing fine otherwise.
https://live.staticflickr.com/65535/55044713035_458b4fc015_c.jpg (https://flic.kr/p/2rS7xst)

Seems to be another bad ground connection. This time on the video amp board. Reseating the tubes and tightening the mounting screws has eliminated the problem for now.

While troubleshooting I did some voltage checks and found that the HV regulation is non-existent. Should be about 22.5kV. I get 19.5kV with brightness all the way down and only 14kV with it up all the way. The raw HV output must be too low for the shunt regulator to work with.

I've already swapped out the 3A3 HV rectifier, 6BK4 shunt, 6CB5 HOT and 6AU4 damper with little change. I'll try the 6CG7 hor. oscillator next. If no improvement, I may just need to pull the chassis again.

I should anyway to make the adjustable HV mod mentioned earlier.

Curiously after sitting overnight, the HV regulation issue improved considerably. Swapping out the 6CG7 help a bit more. Holds fairly stable at about 19.5kV.
Yes, I do need to adjust the efficiency coil. So nice of them to place it behind the HV box between the damper and HO tube. I'll need to fabricate a long adjustment tool.

Just in time for Saturday morning cartoons.
https://live.staticflickr.com/65535/55046361733_14de54d68e_c.jpg (https://flic.kr/p/2rSfZyi)

https://live.staticflickr.com/65535/55046436864_0a19fafccb_c.jpg (https://flic.kr/p/2rSgnTE)

https://live.staticflickr.com/65535/55046362368_3f59fd9572_c.jpg (https://flic.kr/p/2rSfZKf)

Excellent progress. On my CTC-5 Chandler, Mike found charred tube sockets from heat which contributed to nasty problems.

Sometimes the HV regulator without an adjustment circuit will get stuck turned on and lug down the HV.

Interesting. That could very well explain it.

You let Simon Bar Sinister tune your TV?!

LOL.
The linearity/efficient coil slug is frozen. I'll see if I can free it up next time I pull the chassis. Meanwhile it continues to perform well.
I'll touch up the converge once the HV gets up where it should be.
https://live.staticflickr.com/65535/55048022796_b41c08b611_c.jpg (https://flic.kr/p/2rSpvkj)

https://live.staticflickr.com/65535/55048286569_9f08f4286c_c.jpg (https://flic.kr/p/2rSqRK8)