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The equipment I used was the HP8601a Sweeper Generator I bought for $40 (I just picked up anpther one last week for less). Plus an HP8600a Digital Marker. The HP combo was designed specifically for this sort of work and provides five absolutely accurate markers. Plus I needed my trusty 40 year old Hitachi scope (which I got for free). I made the input jig RCA specified and used a genuine RCA bias box I found in a pile of electronic garbage years ago. The alignment was pretty easy and ultimately the results matched exactly the RCA notes. The only issue I had was alignment of the 1st IF tuner link. An open decoupling capacitor in the tuner fixed that. I believe the decoupling capacitor is a common problem and overlooked. Once fixed the process was easy and results exactly as described. The resultant pictures on the 15GP22 are phenomenal... that was before the convergence transformer failed. I will have time to return to that again this autumn. It is all explained in the link below. You don't need special laboratory equipment. Simply a good nose for a bargain and there are literally plenty of equipment bargains about. I still highly recommend the HP8600a/HP8601a combo because they are relatively cheap and produce the highest quality alignment results. Here is the link which includes the process of my CT-100 using the HP equipment. Look at page three where the Video IF section of the CT-100 is in the bucket of water indergoing electrolysis rust removal. If this CT-100 can yield a perfect IF response, then any CT-100 can. :) https://videokarma.org/showthread.php?t=274959 |
UPDATE, November 24, 2024
Greetings Marshall. I started looking at the CTC5 again this evening and I will be attacking the H.V. regulation modifications next. The plan is to install a H.V. adjustment control in place of the Matrix Balance control which is located right next to the 6BK4 regulator tube socket. The Matrix Balance control never worked on any CTC5 that I have ever worked on. Every chassis that followed the CTC5 did away with it and replaced it with 470 ohm resistors at the cathodes of the demodulator tubes, and that is what I will do here. The pictures attached are as follows. Pix 1 The parts that came out of the AGC, SYNC, Audio I.F. board from the last update. I missed sending it at that time. Pix 2 is the 6BK4 Shunt Regulator socket. Notice the control on the right side with a yellow and blue wire. That is the Matrix Balance control that I will remove. In place of it will go a 10 megohm pot that will allow control of the H.V. regulator. I have already disconnected those wires on the other end where they connected to the demod tubes. Since this modification causes changes in the Chroma circuits, I will be doing the component replacements in that section next instead of moving to the Vertical sweep section. I did a random "in circuit" check of resistors in the Chroma section and there are a number of resistors that are out of tolerance by over 20%. So, that will be a slow task since it is all hand wired. One more note. The H.V. as measured at this point in time before mods is 17 KV. I hope to be able to adjust between 19KV and 22KV if all goes well. More to come, Stay tuned! https://visions4netjournal.com/wp-co...SC03198-1.jpeg https://visions4netjournal.com/wp-co...SC03197-1.jpeg Good evening. I have made some progress over the past few days. The H.V. Regulator circuit has been modified. A H.V. control now exists and the H.V. can be varied from 16 K.V. to 23 K.V. I have also decided to eliminate the 5U4 Rectifier tubes in the power supply and replace them with a plug in solid state replacement of silicon rectifiers that are rated at 1000 PRV at 2.5 amps. These plug in replacements can be purchased, but I make my own from old dead 5U4 tubes. I break away the glass and save the sockets and install the 1N2007 rectifiers into the socket which makes it plug in directly to the where the tubes were. These rectifiers take the place of both 5U4 tubes for power handling capabilities. The improvement is power B+ stability throughout the chassis and it saves 6 amps of current not being handled by the power transformer to power the filaments of the 5U4s. Since the solid state rectifiers are more efficient, the B+ increases by around 30 volts so I installed a 70 ohm 50 watt resistor (chassis mount type for heat control), to the top of the chassis where the 5U4's were. Now, on to the Chroma circuits. First thing I noticed is a very badly charred terminal strip where a 10 watt resistor mounts. I remembered this from my own set and it is weak spot that needs to be addressed. The charred terminal strip eventually turns in to conductive carbon and if it doesn't disintegrate first, it can actually cause a small fire. This is a very delicate piece of surgery and the 10 watt resistor that caused this damage will be re-mounted to the top of the chassis where it can dissipate its heat away from the chroma circuits. Very bad design on the part of RCA in my opinion. Basically it is a 10 watt resistor in a 15 watt circuit. I have also installed a 5 amp pigtail fuse in line with the power transformer primary. That should have been done by RCA in the beginning. Pix. 1 H.V. reg 6BK4 socket before mod. Pix. 2 H.V. reg 6BK4 socket after mod with H.V. adjustment added Pix. 3 H.V. adjustment set for 16KV Pix. 4 H.V. adjustment set for 23KV Pix 5 5U4 tubes with solid state replacement at the bottom of the pix. Pix. 6 Chroma circuit with charred terminal strip. Hard to see from the pix. I will send pixs in 3 separate emails. I hope it goes well. cheers, Mike https://visions4netjournal.com/wp-co...SC03197-2.jpeg https://visions4netjournal.com/wp-co....-control.jpeg https://visions4netjournal.com/wp-co...H.V.-16KV.jpeg https://visions4netjournal.com/wp-co...H.V.-23KV.jpeg https://visions4netjournal.com/wp-co...h-SS-rect.jpeg https://visions4netjournal.com/wp-co...charred-2.jpeg The chroma terminal strip will be a very slow and delicate piece of surgery. Lots of wire and re-locating of parts to get the heat away from the chroma circuits. Cheers, Mike |
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Small update.
Mike, Excellent work! Looks like we will have good HV regulation. Peace, Marshall Yes, the H.V. regulation is good. And, I can change it from 16 KV to 23 KV if I want to for best sweep and focus. Tonight I was looking at the chroma circuits a bit and noticed that the R-Y, B-Y and G-Y tube sockets need to be replaced. They are very brittle and have intermittent tube socket connections from many years of heat from the tubes. More on that later. Cheers, Mike |
December 9, 2024
Update. Greetings. I have done many things on the restoration since my last report. A lot of time has been spent on the restoration of the Chroma Circuits. What a mess. But first, let me recap on the last report with details. The first picture will be of the mods in the power supply. Top of chassis showing the two 5U4’s removed and replaced with 1 “plug in” using solid state 1n4007 rectifiers. Also, along side is the 70 ohm 50 watt chassis mount resistor to take care of the increased voltage that resulted in the mod. I also replaced a dual potentiometer for the red/green dynamic convergence. No picture for that. The green section was beyond cleaning. I had a good spare unit in my CTC5 Junk. OK, now to the Chroma Circuits. There have been a number of things to address. One, problem was that the gray scale changed every time I fired up the chassis. Then it would slowly change from red, to green, to blue slowly, then any color and back again. This usually resembles a failing CRT, which is not the case here. I traced this problem to the tube sockets of the R-Y, G-Y, and B-Y / Blanker tubes. (12BH7’s). The filaments were changing in brightness. It was necessary to replace both of those tube sockets. The gray scale is now stable. Another issue with the Chroma rebuilding was a failing terminal strip. In the picture, this can be seen above center in the full view photo. Also shown close up in another photo. The terminal strip overheats due to a big 10 Kohm 10 watt resistor that never should have been installed there. I have moved it to just above the chroma circuits, and away from the sensitive tuned coils. It can be seen in the full view photo just left of center. It looks like a cement rectangle. In the later photo, it is missing because I moved it out and away from the Chroma Circuits. and you can see where I replaced a burned wire with a new white wire. I replaced a lot of resistors that were way out of tolerance, and of course all wax type capacitors. Photo 1 5U4 tubes removed and solid state rects installed. Also, 70 ohm 50 watt resistor chassis mounted for heat dissipation. Photo 2 Chroma strip charred Photo 3 Chroma Circuits b4 component upgrades. Photo 4 Chroma strip replaced Photo 5 Relocation of the 10 K ohm 10 watt resistor Photo 6 Replacement of the 2 tube sockets bottom view Photo 7 Replacement of the 2 tube sockets top view Photo 8 The Chroma Circuits finished with rebuild Photo 9 All the components that I replaced in the Chroma Circuits. Photo 10 CTC5 Color pattern when finished with Chroma Circuits. Next is the Vertical sweep board. https://visions4netjournal.com/wp-co...h-SS-rect.jpeg https://visions4netjournal.com/wp-co.../DSC03220.jpeg https://visions4netjournal.com/wp-co...p-charred.jpeg https://visions4netjournal.com/wp-co...-B4-recap.jpeg https://visions4netjournal.com/wp-co.../DSC03218.jpeg https://visions4netjournal.com/wp-co.../DSC03219.jpeg https://visions4netjournal.com/wp-co.../DSC03215.jpeg https://visions4netjournal.com/wp-co.../DSC03216.jpeg https://visions4netjournal.com/wp-co.../DSC03214.jpeg https://visions4netjournal.com/wp-co.../DSC03213.jpeg https://visions4netjournal.com/wp-co...n-rotated.jpeg |
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I ended up dividing the resistance: I replaced the burnt terminal strip and the 10k with an 820 ohm 10 watt in the same position to duplicate the original wiring and to minimize wiring capacitance changes. I wired in series with it an outboard 9.1K 20 Watt resistor well away from other components. In addition I had to replace the wires which were burnt and insulation crisp. |
From Mike today.
Update, December 22, 2024 Greetings Marshall. More progress here. I finished the rebuild of the vertical/sync board. I ended up replacing every component on the board, including the 7 pin socket for the Vert. Output tube 6AQ5. The socket pins were badly corroded. I will report now, that on every board, there has been some kind of crusty film that needed to be removed. I am not sure what it was but I did a lot of scraping with a small razor tool that I made on the end of a stick to aid the process. Perhaps some kind of chemical that was used by a previous tech, just not sure. I have never seen this before but it is on every board. Again, too there were a number of out of spec resistors on the vertical/sync board. I have started on the video board this evening but no pictures on that one yet. But I can tell you that both of those tube sockets will need to be replaced as well. I get the feeling that this set spent a lot of time in a warm room and was left on for many hours at a time since the tube sockets are cracking from the many years of heat from the tubes. Maybe in a Hotel lobby environment, or something like that, to make an educated guess? Long story short, this set has had a lot of use. Many components out of spec, and many repairs, some of which were not professionally done. You can see a bit of this mess on the picture of the Vert/sync board where components were tacked on top of the board and not installed directly to the holes in the board. Not good practice. OK, here we go with the new pictures. Pix 1 Vertical/sync board before rebuild Pix 2 Vertical/sync board after rebuild Pix 3 Parts replaced on the board Happy and safe Holidays and a good New Year! Mike https://visions4netjournal.com/wp-co....b4-Recap.jpeg https://visions4netjournal.com/wp-co...r-rebuild.jpeg https://visions4netjournal.com/wp-co...-replaced.jpeg Good day Mike, That first pic, what a mess! Beautiful, close to pristine wood cabinet, but a horror show chassis. We have a good 21AXP22, that says something. Best holiday wishes to you and yours, Marshall Visions4 Magazine https://visions4netjournal.com/ |
Update, January 20, 2025
From Mike, I have done a complete rebuild of the Video Board. All components were replaced since I had to do a full scrape of the top of the board to remove some kind of residue from previous repairs. Not sure what this stuff is, but it is not rosin from a solder bath treatment. I have found it on all of the P.C. boards of this chassis. I made a special tool from a small razor blade to help in the process. Also, both tube sockets needed to be replaced. They were both crystalized from heat and the socket pins were exposed from the top of the board. I removed the top cover of the I.F. board and it appears to be clear of this strange residue. I notice a small crack on the I.F. board where one of the mounting screws secures it to the chassis. Fortunately it is not in a critical place of the electronics. It is only a ground, and the ground is good. It bothers me a bit though, that this made it through the assembly line without being caught. However, before this chassis is finished, I will be beefing up all of the grounds on the P.C. boards with wire soldered to the chassis from ground points on the boards. This insures a good ground from P.C. board to chassis. From the looks of the I.F. board, there will not be too much to do in the way of component replacement. I may replace both the Audio and Video detector diodes due to their age but that will probably be all unless I run in to some surprises during R.F.I.F. allingnment. The picures are as follows: Pix 1 Video Board before rebuild Pix 2 Scraping with tool. Pix 3 Sockets removed and board 1/2 scraped of residue. Pix 4 Parts replced on Video Board Pix 5 Video Board after rebuild Pix 6 Video Board after rebuild with tubes installed. Pix 7 I.F. top of board with cover removed Pix 8 I.F. board with crack at mounting bolt. Yet to do: Add grounds to P.C. boards. Replace several more caps in main chassis Make screws for Yoke Clamp. "special" Make up a back cover. Add H.V. cover that is missing. Do AFPC alignment of Chroma Circuits Do R.F. I.F. alingment check and adjust as needed. Cheers, Mike https://visions4netjournal.com/wp-co...4-rebuild.jpeg https://visions4netjournal.com/wp-co.../Scraping.jpeg https://visions4netjournal.com/wp-co...-scraping.jpeg https://visions4netjournal.com/wp-co...-Replaced.jpeg https://visions4netjournal.com/wp-co...r-rebuild.jpeg https://visions4netjournal.com/wp-co...ith-tubes.jpeg https://visions4netjournal.com/wp-co...-Top-view.jpeg https://visions4netjournal.com/wp-co....F.-Crack.jpeg |
Update, January 29, 2025
(Full restoration from start to date or scroll to Update, January 29, 2025: https://visions4netjournal.com/vinta...-tv-page-twoa/ ) From Mike, Greetiings once again. I have added ground wires to the necessary boards but no pictures on that. Not much to it really. I have moved to the high voltage cage to change several caps in the horizontal centering circuits. In the process, I found a number of issues that needed to be addressed in the focus circuit. There was an extra resistor installed that really should not be there. It wasn’t hurting the operation but it was poorly installed and had no purpose so I removed it. Also, there was a resistor missing in the voltage divider for the focus voltage. Seemingly, there was also an extra resistor going to nothing as well. I also removed that one. I used the terminals that were freed from that removal to install the missing 2 meg 2 watt resistor that should be there for the voltage divider. Not sure what all of that was about. ?????? I also discovered some poor wiring on the focus control. A “cold” solder joint that was obviously intermittent mechanically. I replaced all of the wiring on the focus control to original specs. I observed some wax leakage from the flyback and removed what was easy to remove. The pictures are as follows. Pix 1 Top of chassis with all boards rebuilt Pix 2 Chassis bottom without the covers installed yet. (Later) Pix 3 Focus control circuit with extra 56 K ohm resistor Pix 4 H.V. Section before repairs Pix 5 Wax from flyback transformer Pix 6 Cold/poor solder joint on focus control Pix 7 330 K ohm resistor not connected to anything with black focus crt wire mis-wired. Pix 8 Chassis shot of flyback Pix 9 Caps replaced, wiring corrected. Notice 1 Meg 2 W resistor added and black focus wire in defferent place Pix 10 Focus control wiring repaired Yet to do: The tuner needs attention and I have already started on that. R.F. I.F. alignment. AFPC alignment in chroma circuits Chroma Bandpass alignment Make extention for back cover Make new wing bolts for yoke clamp Whatever else I can think of. There must be more. https://visions4netjournal.com/wp-co...s-rebuilt.jpeg https://visions4netjournal.com/wp-co...ut-covers.jpeg https://visions4netjournal.com/wp-co...-resistor.jpeg https://visions4netjournal.com/wp-co...e-repairs.jpeg https://visions4netjournal.com/wp-co...m-flyback.jpeg https://visions4netjournal.com/wp-co...s-control.jpeg https://visions4netjournal.com/wp-co...ted-to-it.jpeg https://visions4netjournal.com/wp-co...t-flyback.jpeg https://visions4netjournal.com/wp-co...lack-wire.jpeg https://visions4netjournal.com/wp-co...-repaired.jpeg |
work of art
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Fantastic job. I'll be referring to this thread as I start work on mine.
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From Mike today,
Update, February 14, 2025 Good Morning. I had to do some work inside the tuner. Two of the B+ power resistors were out of tolerance. The main tuner cover was not installed properly by a past tech so I had to remove the tuner from its mounting assembly and straighten the cover so it fits properly. Also, the cover for the antenna input balun unit was missing.. I had a spare! Here goes with the list of pictures. These will be sent over 3 emails. Pix 1 Parts replaced in H.V. cage. Pix 2 Cover missing on Antenna balun unit. Pix 3 Cover replaced from my spare parts. Pix 4 Tuner 10 K ohm resistor down in value to 7 K ohm. Pix 5 Tuner side view with 10K resistor replaced. Pix 6 Tuner 12 K ohm resistor up to 17 K ohm. Pix 7 Tuner 12 K ohm resistor wide view. Pix 8 Parts replaced in tuner. More to come soon. Mike. https://visions4netjournal.com/wp-co...H.V.-cage.jpeg https://visions4netjournal.com/wp-co...r-missing.jpeg https://visions4netjournal.com/wp-co...are-parts.jpeg https://visions4netjournal.com/wp-co...wn-to-7-K.jpeg https://visions4netjournal.com/wp-co...10-k.res_.jpeg https://visions4netjournal.com/wp-co...up-to-17K.jpeg https://visions4netjournal.com/wp-co...wide-view.jpeg https://visions4netjournal.com/wp-co...-in-tuner.jpeg |
Update, February 22, 2025
From Mike, I have changed the video detector diode which improved the contrast by a fair amount. I also changed a similar diode in the color killer section only due to its age. It was the same part number as the video detector, general purpose signal diodes, 1N64. There appears to be a small problem in the chroma phase circuitry where the hue changes by a fair amount as the set warms up. Not sure what that problem is just yet. When I was doing the AFPC alignment (Automatic Frequency and Phase Control) of the chroma circuits, the hue never came out right which indicated a phase problem. This turned out to be the 3.579545 MHZ crystal was slightly off frequency. After replacing the crystal, the AFPC adjustments came out right, but I am still left with the hue change after warmup. More on that later. Another thing that I am not happy with is the resistor in the power supply that I chose to reduce the B+ voltages due to the solid state rectifiers I installed to replace the 5U4 tubes. I have ordered a better replacement for that resistor. I have done a full alignment of the Chroma Bandpass amplifiers and the RFIF strip. Improvements came from both. I will be working on the new special screws for the yoke clamp and the modification of the new back cover which needs to be made wider for the cabinet. Pictures will be sent over 2 emails. Pix 1 Chroma Bandpass Curve after alignment Pix 2 R.F. I.F. curve after alignment. Pix 3 A good Jetsons cartoon shot to show good color. Pix 4 A shot of a girl from Hawaii 5-“O” w. good yellow! Pix 5 A shot of a flying helicopter on Hawaii 5-“O” EDIT: I changed the Burst Amp transformer and that seems to have fixed the drift. If there is any drift now, it is very minimal. The drift was dramatic b4 the transformer swap. Cheers. Mike. https://visions4netjournal.com/wp-co.../DSC03281.jpeg https://visions4netjournal.com/wp-co.../DSC03289.jpeg https://visions4netjournal.com/wp-co.../DSC03296.jpeg https://visions4netjournal.com/wp-co...4-rotated.jpeg https://visions4netjournal.com/wp-co...3-rotated.jpeg |
Update, March 12, 2025
CTC-5 Update From Mike, Greetings Marshall. We are in the homestretch with this one. Still some HUE shift but that might be my JIG CRT. Replacing the Burst Transformer helped a lot but still some shift of about a 5 to 10 minute warmup. I will be connecting this chassis to my set 21AXP22 crt within the next 2 days. I hope to get a better idea of its performance from that. I hope the Hue shift goes away with that test. I have installed 2 brand new tubes in the sweep circuit even though the ones in the chassis seemed to be working OK. Those tubes are the Horizontal output and damper tubes. 6CB5 and 6AU4. I did this due to their age. I will keep the old ones for test purposes since they still work properly. I feel better knowing that those tubes in the set are new. The yoke clamping bolts were missing so I had to make new ones. They are unobtainable. I was able to contstruct them from some 10-32 threaded rod, some small nuts and wing nuts. J-B Weld epoxy played a big role in the process. If all goes well I plan on delivery of this by the end of this month. I will figure out timing and let you know soon. I stll have to find or make a new cover for the deflection yoke since it has deteriorated over the years. I have a plan in place for that. As for the back cover, I will be finishing that at your house and I will bring all of the materials and tooling to do so. The measurements are still a bit unclear so I think that doing it there is best. I have found the proper chassis bolts so that is no longer an issue. I think the “pencil box” screws are missing also so I will be bringing those too. Pix 1 is what the original yoke clamp bolts look like. I took this one from my set for the photo Pix 2 is the 2 that I have fabricated for your set. See you soon. Cheers, Mike. https://visions4netjournal.com/wp-co...lamp-Bolt.jpeg https://visions4netjournal.com/wp-co...amp-Bolts.jpeg |
The Plan
March 22, 2025 Hello again. Well, things have slipped a bit with the delivery timing. I have been pulled a lot of different directions this month. It is looking more like the first week in April. I have not had time to bring the chassis into the house and connect it to my tube for final evaluation and that really needs to be done. I keep running the chassis on the bench when I am in the shop and it is still rock solid. I may go through the AFPC alignment one more time on the chroma circuits to see if the slight drift in HUE tightens up. Again, I will know a lot more about that when I hook it up in the house. It all may be my jig CRT drifting. Either way, see you soon. Mike |
We are back after a long hiatus and a persistent problem with a hue shift.
Update, June 27, 2025 Greetings. After taking about 6 weeks off, it is time to re-visit this project. There appears to still be a shift in the hue. Cold spray has shown no sensitive components. However, there are 2 capacitors located inside the CW Driver Transformer can. They cannot be accessed with the cold spray so I have elected to change them. I had to order these since they are 5% tolerance and the best I could do is 10% in my stock. There are 2 capacitors in the can, a 680 pf and a 1000 pf both of the silver mica type. The wires on this transformer are very small and delicate so there are no second chances if something should go wrong when changing the capacitors. I also plan on changing the socket on the 6CB6 CW oscillator tube. It is very dark in color and probably should just be replaced whether it is problematic nor not. The pictures will be sent over several emails. Onward! Pix 1 Schematic showing the caps inside the can Pix 2 Bottom view of XFMR Pix 3 Moved several coils out of the way so I can get to the XFMR wiring. This unveiled a very suspicious looking ground connection. Pix 4 6CB6 Osc. socket discoloration. Pix 5 XFMR wires disconnected Pix 6 and 7 XFMR removed and ready for dissassembly Pix 8 External components removed. These will all get replaced with new. Pix 9 XFMR dissassembled Pix 10 The 680 pf cap shown with the 1000 pf behind the coil. https://visions4netjournal.com/wp-co...WXFMRcaps.jpeg https://visions4netjournal.com/wp-co...CWXFMRBot.jpeg https://visions4netjournal.com/wp-co...round-con.jpeg https://visions4netjournal.com/wp-co...B6-socket.jpeg https://visions4netjournal.com/wp-co...ires-disc.jpeg https://visions4netjournal.com/wp-co...removed-1.jpeg https://visions4netjournal.com/wp-co...removed-2.jpeg https://visions4netjournal.com/wp-co...comp-rmvd.jpeg https://visions4netjournal.com/wp-co...FMR-disas.jpeg https://visions4netjournal.com/wp-co...f-showing.jpeg |
Bandpass Cap Replacement
Update July 3, 2024 Greetings. I have acquired the 2 new silver mica capacitors. The following pictures explain. Pix 1 The new 5 % tolerance 680 pf cap. Pix 2 The new cap installed Pix 3 The other cap on the other side, a 1000 pf old cap. Pix 4 New 5% 1000 pf cap installed Pix 5 Bandpass XFMR re-assembled Pix 6 The repaired ground with busswire attached. Next, we install the XFMR and replace the 6CB6 3.58 MHZ local oscillator socket. https://i0.wp.com/visions4netjournal...337.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...338.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...341.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...342.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...343.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...344.jpeg?ssl=1 |
Update July 13, 2024
From Mike, Good morning. The work on the CW Driver transformer is complete. The 6CB6 3.5 mhz local oscillator tube socket has also been replaced. The AFPC (hopefully final) alignment went as expected. 6 photos follow over 2 emails. Pix 1 The CW Driver transformer with the external componects replaced. The old one had to be removed and discarded in order to disassemble the unit for the internal capacitors replaced which was previously described. Pix 2 The badly overheated tube soket for the 6CB6 local oscillator. Pix 3 The socket removed. Pix 4 New socket installed. Pix 5 Chroma pattern after AFPC alignment. Pix 6 Real time image over the air. Best I could do. Onward to cooking it on the bench for a few days. Stay Tuned!! https://i0.wp.com/visions4netjournal...345.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...346.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...347.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...348.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...ted.jpeg?ssl=1 https://i0.wp.com/visions4netjournal...364.jpeg?ssl=1 |
Update July 16, 2025
Good day to all. The last CW transformer and socket repair may have fixed the hue drift. Mike reports after 3 days of cooking the CTC-5, the set is stable. If all continues well, we are looking at a July 22, 2025 delivery. |
The restoration by Mike Doyle was completed today with the delivery of the RCA CTC-5 Chandler Deluxe model to my residence. Watch a 3 minute video to see the results.
The video link: https://videos.files.wordpress.com/v...y-movie-93.mov https://visions4netjournal.com/wp-co.../IMG_1265.jpegUpdate July 20, 2025 |
That is looking really good. The CTC5 Deluxe chassis has wider chroma bandwidth which may partially account for the great performance.
An interesting note: I recall seeing a paper published in the RCA review around 1955 on the effects of quadrature crosstalk in NTSC chroma demodulation. The CTC5 Deluxe chassis stands apart from the CTC4, CTC7 and the chassis's that followed in that the receiver chroma channel sidebands are asymmetrical: that is it is like the I channel in the CTC2 (CT100) chassis. This would lead to greater chroma resolution (approaching 1MHz as opposed to 500kHz on the other simplified chassis RCA sets. The increased chroma resolution would however be achieved at the expense of introducing quadrature crosstalk. i cannot recall the conclusion of the article in the RCA Review. But I alsways wondered if the CTC5 Deluxe chassis was the outcome of that paper. The crosstalk distortion would be evident as an odd coliored edge at saturated color transitions. Eg on vertical edge transitions between colors. Would you be able to to take a close up of a vertical edge where there is a horizontal saturated color transition say between Red and Blue? The CTC5 Deluxe uniquely would be the only color receiver to demonstrate if the improved chroma resolution offsets any minor quadrature distortion present. Here in a 1977 RCA Review paper. I was sure I read an earlier paper about is at the time the CTC5 was being designed. https://www.worldradiohistory.com/AR...w-1977-Mar.pdf |
Pritchard's 1977 paper is excellent, as all of his were. However, the measured results are for the case of a video feed (no R.F./I.F. problems) or the video output of a Conrac receiver that matches the original NTSC assumed IF response, rather than the then-current haystack response that the paper mentions. The results do generally correspond to the relative subjective impressions of the Super and Deluxe chassis. The chroma transients of the Super chassis are generally awful compared to any other RCA before or since.
In some other threads here, I have posted the investigations that I did at Zenith of the possibility of re-introducing I/Q demodulation in later sets to get rid of quadrature crosstalk. The investigation was prompted by RCA's re-introduction of I/Q in their solid state sets, which, however, puzzlingly, had low I-channel high-frequency response compared to the NTSC spec. What we found was that the loose NTSC spec on the Q channel lower-sdieband response meant that some installed encoders put too much lower Q sideband energy in the signal, which was not symmetrical to the 4.5 MHz sound notch that all receivers must have. The result was that some programs had acceptable transients and others did not. We surmised that RCA discovered this and deliberately reduced the I response to prevent visibility of unacceptable quadrature crosstalk depending on the signal source. The new use of I/Q decoding by RCA was short lived, and they went back to equiband decoding. |
I also want to caution that it is very hard to find a true I/Q source today, and this strongly affects any results you might obtain comparing different chassis' chroma transients.
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So Wayne, what I gather is that RCA did later attempt to improve chroma resolution by again using I /Q demodulation only to find that encoders were not limiting the Q bandwidth to 500kHz?
I always wondered in the latter years of NTSC composite encoding whether the true NTSC specifications for 1MHz I and 500kHz Q were still used. Or because the assumption that pretty well all receivers used equiband narrow band (500kHz) chroma demodulation. Your reply concluding that the RCA re introduction of I / Q demodulation revealed too much Q component above 500kHz suggests to me that chroma encoding by the 1990s had abandoned I / Q and simply used slightly wider band R-Y / B-Y. To my earlier question on the visual effects of quadrature crosstalk on transients: how obvious and ojectionable was the crosstalk in the picture? I see no evidence of it on my CTC5 Deluxe which has the wider chroma bandwidth. Perhaps due to an abandonment of I /Q encoding, it is because the encoded signal no longer has an I component from 500kHz to 1MHz? |
So Wayne, what I gather is that RCA did later attempt to improve chroma resolution by again using I /Q demodulation only to find that encoders were not limiting the Q bandwidth to 500kHz?
THE PROBLEM IS/WAS THAT THE NTSC SPEC SPECIFIED ONE ROLL-OFF FREQUENCY 3 DB DOWN, WHEN A SPECIFICATION OF A TRAP ON THE LOWER SIDEBAND CORRESPONDING TO THE UPPER SIDE SOUND TRAP WOULD HAVE BEEN MUCH MORE SPECIFIC. I always wondered in the latter years of NTSC composite encoding whether the true NTSC specifications for 1MHz I and 500kHz Q were still used. Or because the assumption that pretty well all receivers used equiband narrow band (500kHz) chroma demodulation. I THINK CAMERA ENCODERS CONTINUED TO USE I/Q NEARLY TO THE END, BUT OTHER GEAR, NOT SURE. Your reply concluding that the RCA re introduction of I / Q demodulation revealed too much Q component above 500kHz suggests to me that chroma encoding by the 1990s had abandoned I / Q and simply used slightly wider band R-Y / B-Y. MAYBE, BUT NOT SURE. IT WOULD HAVE REQUIRED SURVEYING STUDIOS TO SEE WHAT GEAR THEY HAD AND ITS INTERNAL DESIGN. To my earlier question on the visual effects of quadrature crosstalk on transients: how obvious and ojectionable was the crosstalk in the picture? I see no evidence of it on my CTC5 Deluxe which has the wider chroma bandwidth. Perhaps due to an abandonment of I /Q encoding, it is because the encoded signal no longer has an I component from 500kHz to 1MHz? IT WAS OBVIOUS ON A 19 INCH TUBE. I THINK THAT THE FAILURE TO SPECIFY THE Q FILTER MORE TIGHTLY ORIGINALLY MAY HAVE HAD SOMETHING TO DO WITH DOING A LOT OF VIEWING ON SMALL SCREENS. |
https://visions4netjournal.com/wp-co...7/IMG_8286.png
https://visions4netjournal.com/wp-co...7/IMG_8287.png https://visions4netjournal.com/wp-co...7/IMG_8305.png As requested by Penthode, a few closeups. |
I noticed a “softer” picture, Mike who did the restoration commented that on all the CTC-5 restorations he worked on including his personal set he saw the issue due to the 1st video amplifier circuit being very marginal to drive the final stage. He has a fix which he applied but contrast is sometimes not enough.
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I'd also note that the filter design theory available at the time was based on approximate methods that had worked well for the telephone industry, but didn't have any of the sophisticated controlled trade-offs between amplitude and phase distortion that came some years later. So, a video filter design would start with a first guess and then have to be tweaked.
It is quite possible that the color coder filters developed by RCA had good sideband cutoff in the Q channel but it wasn't realized that this needed to be spec'd in addtion to the rolloff shoulder. |
On DVD’s I tested on this set, some fill the screen, while others do not. Not sure why, but the vertical output circuit just barely fills the screen vertically because they tried to do vertical sweep with with a 6AQ5 audio tube.Mike applied a fix where he changed a different capacitor in the vertical oscillator which overdrives the tube, but it doesn’t hurt the tube.
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If you look at the examples of bad crosstalk in Pritchard's paper, the bad cross talk is only 5 or 10 percent of full level.
The NTSC spec for the Q signal modulation is Less than 2 dB down at 400 kHz; Less than 6 dB down at 500 kHz; At least 6 dB down at 600 kHz. There was no spec for the frequency at which it should be 20 dB down or 26 dB, or whatever would be required to make the crosstalk unnoticeable. |
Another problem they had was with the RF amp section in the tuner but most of that is moot since we drive the tuner with a digital tuner box.
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Quote:
A quick lab check for quadrature distortion is to display a color bar pattern and look at the green-magenta transition, which should be neutral at the center for any decoder, equiband or I/Q. |
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Even the close ups look good. Excellent job!
The only aberration is the blue at the transition in the first photo and the odd transition between the blue and orange in the second photo. The blue is odd and will have to think about it more. The Blue Orange transition is close to quadrature and is interesting. There appears no predominant hue at the transition and looks like luma only. Perhaps it is in the original image. Nevertheless these are only curiosities and does not diminish from the excellent pictures achieved. https://www.videokarma.org/attachmen...9&d=1753593465 https://www.videokarma.org/attachmen...8&d=1753593465 |
Belated report on a mishap which occurred August 6, 2025, followed by recovery. This post, November 5, 2025.
Update, August 10, 2025 On August 3, 2025 I heard a snap sound while watching the CTC-5, but all appeared normal. The set continued to work well the next day and on August 6, 2025 about 1 minute after power up, we lost raster 100%, but we had sound. No smoke, no odor. An anxious call to Mike ensued. The following is from Mike. Greetings Marshall. Since my return on Aug. 3rd to attempt and finally fail to do a repair there, the chassis has returned to the bench at my home. While at the house on the 3rd of Aug, a 3/10 amp flyback protection fuse was found to be blown. You reported several loud snaps prior to the loss of raster on the set. The source of those snaps is still unknown but the suspicion is that there was an arc from the top of the 6BK4 regulator tube which previously during all restoration processes, the H.V. top cover was removed and not installed until the day I returned the chassis on the 20th of July. After replacing the fuse and all of the sweep tubes, I only had weak H.V. (about a kilovolt). And the filament on the 3A3 rectifier could not be seen an illuminated. That is when I decided to return the chassis to my bench for further testing. The first thing that I did was install solid state rectifiers in place of the 3A3 H.V. rectifier and also on the 1V2 focus rectifier. This restored the raster but not with full screen width. About 2 inches short on left and right sides. I also noticed that there was no control over the H.V. by way of the pot that I installed during the restoration. This was corrected by replacing the 6BK4 regulator tube. I now have control over the H.V. I suspect that this tube failed and caused the arcing within the cage but I will never know for sure about the sequence there. No way to know. I have done a number of tests througout the Horizontal sweep circuits and my conclusion is that the flyback has several shorted turns in the primary winding which is causing lack of full sweep and also lack of enough current to supply the filaments of the 3A3 and 1V2. All of the resistance values of the flyback are within range according the the Sams Photofact documentation but a few shorted turns of the very small wire of the primary which normally measures 450 ohms, would be impossible to detect since when the documentation was done sometime in 1956 or 57, digital meters had not yet been invented so precise resistance is only rough for us at the 450 ohms. Since all other parts of the sweep circuit seem to be OK, I will be installing my one (and only) spare flyback sometime in the next couple of days. I hope that it is a good spare. The only way to know is to install it and see what happens. I will be monitoring flyback current when first applying power. This is where we both say a “Hail Mary” Cheers, Mike Update, August 11, 2025 Greetings. The operation was a success. The patient lived. Normal H.V. 21KV (and adjustable). Full sweep and good focus. Flyback current is 220 ma. Same measurement with failed fly was 300ma. All good now. I will cook for a couple of days but for short periods and only at night with this heat. Cheers, Mike Update, August 13, 2025 I have cooked the chassis several more times today. All looks good. Before I changed out the transformers, I used my digital ohm meter to compare the primary transformer resistances in order to further prove that the transformer had failed. The proof was there. The failed unit was 466 ohms and the replacement unit was 491 ohms. So, there is a 25 ohm difference which means a short in the winding. I decided to open up the top of the H.V. cover with 2 big holes for ventilation. It should not compromise any safety issues with fire. After about an hour of operation in the shop with the temps at 100 degrees, the flyback was only warm to the touch. This is a very good sign. Also, the width control switch is now a minimum width instead of maximum width. It is a 3 position switch that selects different windings of the flyback for sweep width. Also a very good sign. My last evaluations of the flyback failure is not only due to the failure of the H.V. regulator tube, but more of long hours of continuous operations in hot conditions. It very likely would have failed very soon anyway. The Sams Photofact calls it out as 450 ohms. Back then, only analog meters were used for this type of documentaion. The RCA print does not call it out at all. As a point of reference here, I am including more numbers for the flyback. RCA printed what was known as the “drawing numbers” on almost every part. Those numbers are different from the actual part number. So, if we go surfing on the internet for a transformer, both numbers need to be known and displayed. Here they are: RCA Part number is 102132 RCA Drawing number is 1106255-1 Pix 1 Failed flyback on left and repalcement on right. Pix 2 Same with other side view. Pix 3 Modification for H.V. cover. https://visions4netjournal.com/wp-co.../IMG_1834.jpeg https://visions4netjournal.com/wp-co.../IMG_1835.webp https://visions4netjournal.com/wp-co.../IMG_1836.webp Update, August 17, 2025 Mike came to the rescue and returned the CTC-5 chassis with a replacement flyback transformer from his donor chassis and all is well. The contrast is better with the new flyback and Mike noted that the horizontal sweep control is set at minimum range which is an indicator of a stronger flyback. He said the old flyback that failed, had the sweep set to maximum to sweep the horizontal raster. One week later, August 24, 2025. New screenshots and a video clip from Wizard of Oz. We compensated Mike well for the restoration and I’m grateful for his generous donation of his personal back up flyback for his CTC-5. Now on hunt for a CTC-5 donor flyback to pay it back. Tap on below image to watch a brief video from Wizard of Oz on the RCA CTC-5. https://visions4netjournal.com/wp-co.../IMG_1837.webp https://videos.files.wordpress.com/Y...s/mah01896.mov https://visions4netjournal.com/wp-co.../IMG_1838.webp https://visions4netjournal.com/wp-[I.../IMG_1841.webpcontent/uploads/2025/11/IMG_1839.webp[/IMG] https://visions4netjournal.com/wp-co.../IMG_1839.webp https://visions4netjournal.com/wp-co.../IMG_1840.webp |
We are looking for a CTC-5 replacement HV flyback for Mike Doyle’s chassis.
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Personally on added holes that big if I were worried about fire suppression I would cover them with metal window screen on the outside of the panel....Fine mesh stops open flame from passing through it....It's why air filters for carbureted car engines often had screening wrapped around them to suppress firey back fires out the carb.
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Gorgeous!
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