The Set: Pete Deksnis's Site about the CT-100
Restoring a Vintage Color Television Set
News & Notices
For a silent, shaky view of
CT-100 s/n B8000194
showing a minute of Rita Hayworth
in the 1944 Technicolor (3-strip) motion picture
Cover Girlclick here
Here's one that missed my peripheral vision two years ago:
"Wired" readers voted the CT-100
...The Greatest Gadget of All Time...
for launching television as we know it today.
Only the second CT-100 to be cobbled together from donor parts proudly takes its place on the Living CT-100 list. Would it be sacrilege to call these 'Frankenstein' sets? Probably. But the name may stick! And as number 136 on the list, this set joins the 35 other Merrills that have operated during the past nine years. Here is the parentage of this set. From Don's email:
Kirk and I lit up yet another working CT-100.
This one was an assemblage of components gathered over a few years:
Chassis from Harry Poster,
Wiring Harness from Pete Deksnis,
Conv and Focus knobs from Jeff Lendaro,
Cabinet from ETF-Steve McVoy,
Cages by Fred Hoffman,
15G from Wisconsin,
Recap by Don,
Troubleshooting and "Make it Work" by Kirk Stankiewicz,
Matching Cabinet, top and insert #26,
15G a bit soft; needs more conv and purity adj.
The other example, known as Tim's Millennium Merrill, can be seen
Eight years ago a puzzling picture of an early 15-in. color set appeared on the first Tidbits page. For answers to the what and who of it
Like stories? Like stories about CT-100's? Then you'll want to read this latest entry to the information exchange page. To jump there,
, and scroll down to Gilbert's latest entry (dated 9-17-08).
In an effort to squelch the dearth of activity on this site recently, I have added an interesting picture of the 15GP22 with its base remove. This is a step along the long path towards rebuilding our coveted 15GP22 tricolor CRTs. Scroll to the bottom of the page after you
For a quick check of the June rebuild results
The first attempt to rebuild a 15GP22 in probably 40 years is scheduled for June10 out at Hawkeye using a new 20-pin stem and a professionally rebuilt 15GP22 gun. The event will be recorded on video.
For more background information, see John Folsom's report on the Early Television Foundation website.
Here's the text of an email received a few days ago. Thought you might be interested in my reply.
HI PETE: I really enjoyed reading and looking at your restoration pictures, Can you please tell me at this time why they are able to restore or rebuild the 19VP22 and not the 15GP22. I have the chance to get a unrestored ct100 with a bad crt and I have found a used untested 15GP22 that is in good looking physical condition, but not sure about taking the investment risk if the crt is no good. thanks chip
THOMAS CHIP FOLEY
Just back from the ETF convention in Hilliard OH. Much discussion about rebuilding the 15GP22. We are considering a compromise between a pure 15GP22 rebuild and one incorporating techniques from the successful 19VP22 rebuild.
Big difference is convergence: the 15G is electrostatic, but the 19VP22, the 21AXP22, and virtually all other early color CRT's are magnetic.
A relatively large quantity of NOS guns for the 21AXP22 are available. That is what was used for the 19VP22 rebuild.
Unfortunately, the company in Georgia, who made a pilot run of 15GP22 guns, is no longer willing to rebuild more. We therefore must somehow accommodate the 21AXP22 guns for use in the 15G rebuild, and that's the challenge.
We are considering recovering a convergence element from a dud 15G and welding it to a 21AXP22 gun assembly.
Another approach is simply to use a 21AXP22 gun 'as is' for the rebuild and live with static convergence only. This would bring the 15G's back to life rather easily compared to other solutions and at normal viewing distance would 'look' acceptable.
So, the quest continues. All elements are in place to attempt the first rebuild with one of the two existing rebuilt 15GP22 guns. Much depends on Scotty's availability.
Next, can you tell me more about the CT-100 you've discovered? As you know, I keep a list of all known surviving sets.
On the eve of ETF 2008 another CT-100 comes to life. Mike has Merrill B8001399 glowing again with plans for final set-up including convergence, matrix alignment, RGB screen, background, blue and green video drive adjustments. Congratulations Mike. For screenshot,
A 15GP22 tricolor CRT uses a 20-pin socket because of the high 12-kV electrostatic convergence element voltage that is applied through the base. The pin conducting the convergence voltage is isolated from other functional pins by six unused pins (three on either side of pin 13). So, the common 14-pin sockets used on 21-in. roundies (21AXP22, etc.) can't be used with a 15GP22, 15HP22, 19TP22, and other of the rare tubes with electrostatic convergence. For new information on the hard-to-find sockets,
Here's an example of why early-color TK-41 operators would compensate for partial image loss in color sets with round CRTs.
The round 15GP22 in a CT-100 cuts out areas of text generated by a typical ATSC-to-NTSC set top converter box. Such losses carry over to program material as well. It's something roundie caretakers will have to live with,
 Polarman, AKA Rich, provided an amazing historical picture of a Thomas Electronics Inc. branded 15GP22 (Rauland built) in a company-built test fixture.
 And, to build upon the January 31 entry, I am following up on another exciting Model 5 discovery right here in my home state, New Jersey, involving not one but two more of the beauties. One was the daily color watcher until 1965 and the other acquired as, imagine, a donor for the other Model 5!
[click here for TEI 15GP22 and scroll down to the fifth photograph]
In the first eight years this site has existed, three more of the rare, pre-production RCA Model 5 color television sets were unearthed. These are in addition to the two original survivors, one of which can be seen in operation at the Early Television Museum in Hilliard, Ohio.
Two of these three newly discovered Model 5's were found in the Manhattan area where NBC is located.
Recently, a fourth Model 5 was identified. It too has a short caretaker lineage that is traced back to early NBC-RCA personnel who lived in New Jersey and worked either in Manhattan or at the RCA Labs in Princeton, New Jersey.
Now half-dozen in number, these CT-100-like sets are among the most sought after early color television receivers. Two of the six are operational.
Selecting the right source material to show off your vintage color TV is important. Here are some of my choices. Look for a comprehensive list upcoming on Ed Reitan's site. For three of my current favorites,
Only a handful of the RCA model 21-CT-55 have survived the ravages of time and landfill, according to our latest list of chassis serial numbers for what is essentially a 21-in. CT-100. Data accrued so far suggests only about 3000 were made before the CTC-4 replaced it in 1955. The newest known 21-CT-55 had its 21AXP22 replaced with a rebuilt 21FBP22 in 1965 (when they cost $45). This set was
in a shop and used for two years, then spent the next 40 in attic storage. Now under restoration. Chassis serial number B8802897. For the complete list,
John Folsom recently received a report from Scotty at Hawk-Eye Picture Tube Mfg., Inc., the hands-on CRT re-builder for our 15GP22 duds. A successful effort to evacuate and seal a 15GP22 was realized. This test was undertaken to gain experience using the vertical lathe required by the 15GP22. Performed with a dud that contained a simulated gun assembly, the goals of the procedure were to make the two new neck welds, evacuate, then run the 15GP22 back to ambient temperature without damage. Credit is given to the new cams that stretch the cool-down time for the CRT as was done with the original 15GP22 manufacturing as read in vintage documentation. While the glass weld at the stem end of the neck is satisfactory, the front weld technique is still being evaluated.
We are encouraged by this development and Scotty's dedication to this project.
How'd you like to be in this guy's shoes?
From the caretaker of Merrill B8003757:
I just got back from a requisitioning mission to my old farm home. I went straight to the attic of the old house and there sat a big box with FRAGILE all over it and some Railway Express labels from Barry Electronics in NYC. Inside, in the original box, is one brand new 15GP22 with good looking getter flashing. I have not unpacked it to see what the serial number is. How's that for NIB?
A CTC-2 in a Merrill at the Radio & Television Museum, in Bowie, MD becomes the 33 operational CT-100 and the 123rd known. It becomes the 'oldest' set in the Living CT-100 list. From Brian Belanger, Curator of the museum: "The Radio & Television Museum (www.radiohistory.org) has a CT-100 that we just restored both cosmetically and electronically."
Both CT-100 and 21-CT-55 chassis serial numbers are now available at convenient links on the
This is one for the record books. An operational CT-100 sold on eBay for $9,623.00 to a collector in France, Jean Francois. Number 122 on the Living CT-100 list, the set has a history. It performed at a UCLA Archives Exhibit during the 1982 SMPTE Conference.
7-9-2007. Today I received more information about that conference from attendee Steve Dichter:
Ed Reitan and I were much involved in that UCLA Archives exhibit in 1982. We planned, designed, and along with our small crew, transported and set up all the early TVs and equipment displayed at that SMPTE conference at the Century Plaza Hotel in Century City.
Here is a home video capture (VHS) of that CT-100 powered up at the conference. A color video of the Red Skelton show was shown. The set performed flawlessly over the many hours it was on. Many old timers, even back then, marveled at the exhibit and especially enjoyed
The whole UCLA exhibit was packed with equipment, including a cosmetically restored TK-41 camera, Ed's
CBS-color receiver, an early CBS field sequential color camera, an RCA experimental triniscope color receiver, and even a pre-war set.
I can't believe it was 25-years-ago already. --Steve
Must have been quite a display, Steve. Wish I could have been there. --Pete
CT-100 number 118 on the Living CT-100 list has just been restored to full color operation by Steve Kissinger. Chassis serial number B8003733. This set was in the hands of Harvey Bartel since the mid '50's when he paid $375 for it. Congratulations to Steve for his restoration of this, the 32nd operational Merrill.
 I have updated my argument assigning the RCA CT-100 as the first color television set. This is based primarily on the number of sets manufactured rather than on whomever may have had a piece of color television hardware to showcase in a store. Jump directly to the newly updated page,
 Found at a Denver yard sale a few days ago by a dedicated radio collector who bought it for a few bucks because it looked "very 50s-ish" this Merrill lost no time making itself known to the vintage color TV community. It's B8002510, the 121st Merrill on the Living CT-100 list, and the stuff dreams are made of.
I have redesigned, rewritten, and updated a page on serial numbers used by RCA to track the CTC-2 chassis and 15GP22 tricolor CRT and linked it to the information exchange page. To jump directly to the newly updated page,
There was a CT-100 that remained unpowered from the time it left Bloomington in 1954 until the early 1990's. Here is a brief accounting of The Virgin Merrill.
I had occasion to participate in a television history display at a local historical society around the early 1990s. I had most of the good props and was working on the 50-year history KTVX in Salt Lake City where I was Chief Engineer. As we were building up the display, a very old RCA dealer from a remote community shipped us two RCA color sets. One was a CT-100. He had stashed several models along the way and this CT-100 had been put away brand new and not turned on since its birth.
I was asked to see if it would operate as the society had some desire to have sets operating during the display, which went on for about six months. The dimwit movers managed to break the tuner knob on the CT-100, but otherwise it was still a virgin. With a set of rabbit ears connected to the CT-100, I plugged it in and turned it on and there was a great, reasonably bright, and not all that far out of purity and convergence, color picture. I did a gentle degauss and the set looked just fine.
The society ran it steady for several days before I finally convinced them we needed not to use it up.
They are still in possession of it, and I have not been able to talk them into letting me have it for some trade of value. It is stored away deep in a basement. It hasn't been powered up since the display. --Jim McDermaid
This became the 120th Merrill in the Living CT-100 list.
The kid's show
began broadcasting in color on September 12, 1955. There is a clip from an early color Howdy Doody show in Tidbits VI. Question: Was this the first scheduled color broadcast on September 12, 1955? To check out the clip, scroll down to the bottom of Tidbits IV after you
Here's an article about the recent 2007 ETF Convention presentation
How good can a picture be on a 15GP22?
. The page also contains colorimeter data taken on the 15GP22 'test fixture.'
Active lists of all known CT-100 and 21-CT-55 chassis serial numbers are available on this site in the old CT-100 serial numbers page:
There is a fifth Model 5. It is an NBC unit that has a large pencil box and so may be the earliest set of this type known. The set is to be featured in the June 16, 2007 Estes Auction.
From Jim Menning:
It is labeled National Broadcasting Co., Inc, Engineering Department, and CT-1. It has two cabinet numbers, 19 on the cabinet, and 31 on the lid. It has a 'pencil box' larger than that on the RCA CT-100.
Word of this set caused quite a stir at the recent ETF Convention when the CT-1 designation was interpreted as a possible 'Model 1.' A rumour quickly put to rest when the first photographs were received. A very rare early color television set nonetheless.
2007 ETF Convention. What a treat. The biggest ever.
One more serial number has been added to the 21-CT-55 list to bring the grand total to... twelve! Nevertheless, this latest number falls smoothly into the existing set and supports the contention that only about three thousand 21-CT-55's were built
This latest Merrill was 'discovered' at
The Museum of the Moving Image
in New York City. To see the 117th known CT-100,
I use Digital Video Essentials to generate color bar patterns and other test signals for my CT-100. Navigation through the consumer verbiage can be a frustrating. Here is my system of DVE navigation,
A simple data base of all the CTC-2 chassis serial numbers that I have amassed over the years can be inspected on this site. There are sixty CTC-2 serial numbers in the list. That is just over one serial number for every two CT-100's identified. Maybe a NUMB3RS-type person can make some interesting hay from the data
In addition, at date of publication, there are twelve known CTC-2B-based sets, the 21-in. RCA 21-CT-55 from late 1954. A simple data base of all the CTC-2B chassis serial numbers can be inspected also. Each CTC-2B chassis in the small list has been restored except for donors
There's another update to the vintage wide-gamut-color quest page. Click on the first 1-28-2007 link below and scroll down to 28 February 2007 at this icon:
Another Merrill has surfaced from a 40-year stint in an attic. Number 116 on the Living CT-100 list, this Merrill may be headed for eBay in the near future.
Here's a new page added to the How-It-Works section describing my pursuit of vintage wide-gamut color television,
For information about a rare CBS RX-90 that recently sold on eBay for a premium price,
(1) Happy New Year everyone, and it's Rose Bowl Parade day as well. Three lucky caretakers can watch the 2007 parade on the same RCA Model 5 color television sets that mesmerized the lucky few watching the 1954 parade 53 years ago. Others will be content viewing the parade on the thirty-or-so operating CT-100s. For my CT-100 screenshots of the 2007 parade
(2) I managed to finish the year investigating a replacement inductor for the CTC-2 chassis. For the report
(3) And at the end of the day we received word that CT-100 caretaker Steve Dichter got some deserved credit. In previous years, going back to the TK-41 era and up until the early 80's, Steve Dichter staged-managed many of the yearly telecasts of the Rose Parade for KTLA. His historical contributions to the 2007 broadcast earned him a place in the credits this year.
Congratulations Steve. And Happy New Year to all.
Last month on the 22nd I started a new Tidbits page, but didn't launch it officially till now that it's been 'fleshed out' a bit.
Historian Ed Reitan has updated his chronology of the CBS Color Television System. Based on his thirty years of research, you can view the updated page on his site,
A bit modern for the 15-in. color set theme of this site, but the newest Tidbit documents an important process for many 21-in. roundie collectors. Scroll down to Ka-ter-aK after you
A period schematic showing modifications to a b&w Admiral was added at the bottom of the 1951 Admiral “color ready connector” page.
A Call for Information.
This is one of two known Stromberg-Carlson 15-in. color television sets that survived the pitfalls of time and landfill. It is the model K-1, introduced ostensibly in time for the January 1, 1954 Rose Bowl Parade color broadcast.
With the rebirth of a stillborn color TV system from 1951 -- the FCC-approved CBS sequential color-wheel system -- it behooves us to use correct historical terms in our discussions. Historian Ed Reitan interprets and defines terminology as delineated by CBS testimony at the FCC hearings. Click here and scroll down to
"Whirling Wratten Wheels..."
Again, here is an update to my experience with a newly manufactured vertical convergence transformer for my CT-100. It's in the Restoration Log section of this site. See the July and September link
A newly discovered Merrill is of interest in that it has five UHF strips installed by the original owner. It was acquired by its current caretaker in 1975 (with a spare chassis in the late 80's) and was last operational in 1994. Number 115 on the Living CT-100 list. Undergoing restoration.
There is solid vintage documentation that describes a longer cool-down period during the evacuation phase of original 15GP22 manufacturing, including specifically why. But nowhere has a reference been found that states how much longer that cooling cycle is. It is therefore a small creep forward in the rebuilding protocol that a cool-down period has been agreed to by all parties.
And here is an update to my experience with a newly manufactured vertical convergence transformer for my CT-100. It's in the Restoration Log section of this site. See the July and August link
Since this site started in 1999, only thirty operational CT-100s have been registered. Like a comet tail that dissipates over time, surely not all 30 operate today. But for the first time this year, another has come back to life. The 31st operational Merrill was recently acquired from a California source and now resides in Florida. Number 107 on the Living CT-100 list, B8002767 again produces 1953 NTSC color.
John Folsom has written the most concise report on the 15GP22 rebuild effort to date.
For sale on eBay, hitherto unknown Merrill is 114 on the Living CT-100 list. Dud CRT.
Moderately late production unit. Would be configured with all known production changes.
8-5-2006: Only once before in earlier eBay history has there been as great a bargan for a CT-100. One-thousand twenty five dollars took this Merrill.
Current project in the 15GP22 rebuild quest is the fabrication of a Teflon/steel ‘necking pin’ for use in Scotty’s vertical lathe. This piece is projected to become available this August.
In a now near-vintage 1980's attempt at Dunbar to rebuild two 15GP22s in California, this 15GP22 was also vertical. The venture was only partially successful; the tubes became operational but went to air in a few short weeks. No attempt to rebuild the guns was made in this undertaking. Photo courtesy of Charles (Kaye-Halbert TV from AudioKarma) who undertook the venture along with other California collectors.
1. The Color Wars page on this site has racked up a few thousand hits rather than the otherwise expected few hundred for a buried page, such as it is. That's because a resource-link from a multimedia-based IT course brought in the 10-fold increase in traffic in recent years. A recent addition to Tidbits V chronicles my bout with a 'color ready' 1951 Admiral. Here's the modified-for-general-use version as linked to from the Color Wars page.
2. Expect up to four more CT-100's to be added to the Living CT-100 list soon.
3. Not much movement on the 15GP22 front as yet.
4. A 15GP22 just discovered has the latest build-date from 1954 yet documented: 4-43, late October, 1954.
With dud 15GP22's going for hundreds of dollars, it'll be interesting to see what one goes for when its wrapped in a Westinghouse H840CK15.
Winning bid: US $1,868.00
A hitherto unknown CT-100 has been found. Number 111 on the Living CT-100 list, this set includes a log book from its service as an RCA display set that includes locations, dates, and technical data. Set was shown in the Waldorf-Astoria, for example. 15GP22 believed to be under vacuum.
Well, I'm back I think. After a lifetime of no hospital or surgery, made up for all that clean living with two nonrelated surgical procedures in February. Never fear. I'm still as modest, quiet, reserved, retiring, and comely as ever...!
Here’s a direct link to a Tidbits V addition showcasing some of my CT-100 screen photos and stuff collected over the last five months.
Why care that a big building in Bloomington is brewing hamster cells in bioreactors? Scroll down to "Time Marches On..." after you
In 2001, vintage RCA color television set model CT-100 serial number B8002177 was given by Jim Fries of Seattle, Washington, to Jonathan Winter, curator of the American Museum of Radio and Electricity in Bellingham, Washington, for permanent display at the museum. Later, NIB 15GP22 serial number IL 2017 was sold to the museum by Javier Dimas of Los Angles in 2004 after he contacted THE_SET with questions about its historical significance. In a December 30, 2005 email, Jonathan Winters reported the museum’s CT-100 to be operational. And so, for the New Year, there’s a newly operational Merrill — our thirtieth.
Here’s a timeline built from email and Living CT-100 records,
After a relatively quite time for new additions to the Living CT-100 list, another lead bore fruit. Merrill B8002899 has served WCIA-TV in Champaign, IL for many years. Number 110 on the list. This set is modified with an
; more information as it becomes available.
B8002899 on display
today at WCIA-TV.
(1) The number of known CT-100 television sets is documented in a Living CT-100 list. As of December 18, 2005, the totals are: 109 Merrills with 29 fully operational, a gain of three and one respectively. These new additions are all in California.
(2) A cam that can control the rebuilder's oven during evacuation of a 15GP22 is still under development. When available, this custom cam will limit temperature to 300 degrees C and greatly increase the time it will take to raise and lower the temperature.
A Merrill already displayed on this site has changed hands, been restored, and hit the hall of fame. For a look at the latest reincarnation of a CT-100,
Two new light items have been added to Tidbits covering the viewing of vintage color television sets.
for 'The Science of Controlling Reflections had not been perfected for Early Color Television' and/or 'How to Take a Screenshot: Do cousins of color bars -cartoons- make good subjects?'
With the successful restoration of B8000194, I've added some operation-based material to this site. Find a new page devoted to CT-100 troubleshooting
. A measure of CT-100 matrix alignment results can be found
. And a bit of light exposure in Tidbits V with
Now Just a Damn Minute...
New material added to the restoration log covering the state of restored CT-100 B8000194;
From the 8-20-05 entry:
"Recently (the last year or more) effort was extended to connect a stem to a neck from an old, dud 15GP22. This has been done although I'm not certain the technique is as reliable as, say, the rebuilding of the electron gun. But the process has been successfully demonstrated."
Another two new stems have been successfully welded to neck glass in another positive step toward developing a successful 15GP22 rebuild protocol.
RCA was just one of the companies to showcase NTSC Rose Bowl color on January 1, 1954. For some documented others,
Yet another Merrill has been added to the Living CT-100 list; it is the 106th known CT-100 and is the first such addition gleaned through the VideoKarma
Vintage Color Television forum. A second Merrill unearthed via the forum is in the process of being confirmed.
Another Merrill has been added to the Living CT-100 list; it is the 105st known CT-100 and is in California.
New items added to Tidbits.
A small set of 2005 entries appears at the end of
beginning with the CTC-5 audio circuit.
+, on the 15GP22 rebuild front, a new, custom-made cam that controls the slew rate of the baking temperature has been ordered. After a few more hurdles (probably most of them as yet unknown), the rebuild team will attempt an engineering evaluation run using a damaged 15GP22 before a bona fide attempt is made to bring a rebuildable tube back to life.
Serial-Numbers:Date-Codes. Part fact, part speculation. Get right to the point, scroll down the page to the last paragraph after you
Here's a super-condensed report on the first six years of 15GP22 rebuild effort. It was my response to a question in the Early Color Television forum at AudioKarma.org:
A process to rebuild a no/low emission 15GP22 electron gun assembly is perfected and in place. Ditto the manufacturer of glass stems. Basically, rebuilding the gun means replacing the old filament and cathode with new ones.
Recently (the last year or more) effort was extended to connect a stem to a neck from an old, dud 15GP22. This has been done although I'm not certain the technique is as reliable as, say, the rebuilding of the electron gun. But the process has been successfully demonstrated.
What's being done now? The archives have yielded a bit of vintage 15GP22 data covering the baking temperature and slew rate of that baking heat. They are different from what is done today. Finding a way to reproduce the vintage procedure is the present challenge.
Living with 1953 Living Color
For some photographic examples of my first session with restored and aligned CT-100 B8000194
Finally made the time to complete the restoration of CT-100 chassis B8000194. The solution to the Andorian effect was right under my nose! To catch the story at the bottom of this latest Restoration Log page
Personal stuff has kept me from my restoration duty this past month. Hopefully, the past is not prolog and I'll be back to complete the restoration of B8000194 quite soon.
On this site, there are instructions for adding fuses to B+ lines of a CT-100. Here is a page in the information exchange section with a new photo showing the installation of a fuse block on a Merrill under restoration in 2005.
Read an update to the restoration log,
(1) I await L42, a 22-uH inductor, now in the mail from mouser.com.
(2) A conundrum concerning components in the High Voltage cage has been solved. A
will take you right to the horizontal sweep page in the Theory of Operation section. Look for a 6-24 update near the bottom of the page.
My restoration of CTC-2 chassis B8000194 is, well, progressing the same way that Opportunity dug itself out of a Mars sand dune recently… slowly but steadily.
We’re now t’shooting the color sync section, which seems to have a five-decades-old tough-dog problem that resulted in blanket rebuilds of video and color sync circuits back in 1956, but to no avail. (Also, someone, maybe that servicer, melted a focus pot when he bypassed a fuse that protects the HV cage and got old ‘194 seriously ‘retired’ from active repair.)
The restored HV circuits are up-and-running and reliable, as are the convergence and focus functions. The set displays great video in
black and white
. The set now isolates the color burst from the detected video and amplifies it properly. Although there is hopefully only a single-point failure mode, as with any faulty closed-loop circuit, this one develops multiple symptoms. Some of them:
>A color subcarrier tank in the reactance-tube plate circuit so far has no clear effect on the phase of the crystal oscillator.
> When rotated, the Hue control can usually kill the crystal oscillator when the plates of the Hue control, variable capacitor 2C186, are meshed about halfway (no, the plates don’t touch).
>The quadrature transformer is easy to align and its output level is fine, when the CW signal is there to feed the phase detector. Yet the dc level from the negative side of the phase detector is often too low, which affects the next entry.
>The color killer can improperly drive the chroma amplifier to cutoff even when a color burst is present. That’s not because the killer circuit is bad, but because the negative level from the phase detector is usually six to eight volts too low… but not always, so the killer biases the chroma bandpass amplifier ‘on’ sometimes... thankfully enough to see that it’s doing its job and amplifying the chroma signal.
Still, the AFC doesn’t yet phase-lock the crystal oscillator to the burst. So, it’s back to the bench for me. PLLoops? @#$?%&!
By the end of the day, May 9th, two basic garden-variety problems were detected and fixed. A good cleaning solved the touchy Hue control, and the sometimes-on sometimes-off color killer was caused by the negative chroma sync phase detector, the triode half of 6AN8 V28. It worked fine when first powered up, but began to fail slowly after two minutes till the rectified signal was not generating enough negative voltage to keep the killer cut off. A new V28 is in place. The color sync section has been aligned; tomorrow we'll see if the AFC is doing its job after the chassis goes back in the cabinet.
6-10-2005 update: The AFC is not yet doing its job because the slug in the color subcarrier tank for the reactance-tube plate circuit is frozen. I have disassembled the unit (L43) and will attempt to repair it, rather than replace it with a transformer from the donor chassis.
6-11-2005 update: The repair went well; the AFC now locks the subcarrier oscillator to the color burst, as seen on a modern dual-trace scope (thanks, Bill, for the loan). After the chassis was returned to the cabnet and connected to the 15GP22, chroma is clearly stable, but it displays wrong colors; will tackle what may be the last problem before final alignment is started.
9-17/19-2005 update: Well, early this morning I finally witnessed Conan O'Brien’s red hair by manipulating the color oscillator phase manually; however, when the color AFC takes over, it's back to
. A check of a vector diagram shows the difference between a shade of red and one of blue can be about 90 degrees. Similarly, a shift between blue and green can also be about 90 degrees. Accordingly, I will locate and order a replacement inductor L42 [Sams], which is part of the reactance tube circuit.
First, Happy Birthday to my son, Daniel, who has been a brave and resilient warrior these last three years.
Food-for-thought added to the Restoration Menu page. Jump to the link to read my musing on
repair or restore?
After nearly five years, I've finally closed the most recent Restoration Log page. To read what prompted the last entry of a page that opened in October of 2000,
Bruce has successfully spot-welded a gun from a dud 15GP22 onto a new stem, and the assembly is being shipped to Scotty for another attempt at developing a process for rebuilding the 51-year-old gems. Each failure sheds a little more light on the path.
It's maybe 75 miles between Omaha, Nebraska and Hiawatha, Kansas. Omaha is one of the few cities that had a station and network facilities for color television in 1954. Hiawatha is a small Kansas city. But in 1954 it had McQueen TV. Jim McQueen sold bright new RCA television sets. Back then, he had a CT-100 on his showroom floor. It never sold, but became a curio over the years, inspiring many nostalgia sessions. Jim kept the set operational most of the time, including up to the time when he finally closed his shop and retired.
Jim's Merrill was finally sold. Randall Pallesen is the current caretaker. In his own words, "I purchased this one from the TV store that purchased it new for resale. Jim McQueen retired about 10 years ago and this TV was on his showroom floor. I purchased the set in perfect working order, and I have a complete set of tubes and the manual. Jim was kind enough to perform a tune up job prior to my picking up the set. I would estimate that this set has less than 100 hours use. So, one more is alive!"
Number 104 on the Living CT-100 list, this set is also listed as operational.
Center-tapped wire-wound pots and 15GP22s. What the restorer needs is often a pain to acquire. Try finding a vertical convergence transformer. Fact is, it's now easy. John Folsom has engineered and manufactured this hitherto unavailable vintage part
Notwithstanding challenges keeping the beasties glowing, we've never gotten a report from an operational CT-100 caretaker whose set failed and who asked to have it removed from the operational category. Certainly some of the sets on the Living CT-100 list have hiccupped now and then; however, this list does reflect those CT-100's that have been made to shimmer in Living Color since this site began in 1999. Number 26 on that exclusive roll was brought to life and is being maintained by Kirk Stankiewicz who acquired his Merrill in 2003 and who was later able to add an operational 15GP22. Congratulations Kirk for your considerable involvement in keeping historic color alive.
1. We await the opportunity for a discussion between the rebuilder and stem manufacturer after the manufacturer successfully bonded a new stem to a piece of neck glass from a dud 15GP22.
2. For those fortunate enough to have a good 15GP22 or two lying around, a procedure for replacing the aquadag coating has been added to the simplified theory section at the bottom of the 15PG22 page. Jump there,
Who was really first? I've added a soapbox piece to the contributor menu (click just above the second animation)
click here for the menu
There is news brewing. A bit of 15GP22 rebuild information should be forthcoming shortly...
There are now 102 sets on the Living CT-100 list. This most recent Merrill is in California.
I recently found a CT-100 that had been languishing in a garage for the past 30 years. It is now at my home in Grass Valley California and is being prepared for full restoration. The serial number is B8003603."
Preliminary good news here is that the set included a spare 15GP22. Unlike so often happens, this tricolor IS still under vacuum. The tube in the set is full of air, but the spare 15G still has black getter flashes indicating a rare and welcome find -- a newly discovered and good 15GP22.