Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Early Color Television

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #76  
Old 12-09-2005, 03:50 PM
old_tv_nut's Avatar
old_tv_nut old_tv_nut is offline
See yourself on Color TV!
 
Join Date: Jul 2004
Location: Rancho Sahuarita
Posts: 7,184
Very interesting, Pete! How does the comparison look on a gray scale now?
Reply With Quote
  #77  
Old 12-09-2005, 05:35 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
It seems the gray scale is a bit contaminated because the color control will not kill it completely, and so I don't have a recent shot. I will have to confirm this w/a scope, however, and try for one Monday morning. Last weekend, channel 13 ran pledge programming during their usual color bars. Hopefully they'll have raised enough $ to go back to color bars this weekend.
Reply With Quote
  #78  
Old 12-13-2005, 09:11 PM
Tom_Ryan Tom_Ryan is offline
VideoKarma Member
 
Join Date: Dec 2005
Posts: 189
Automatic balck level and white balance

Quote:
Originally Posted by Pete Deksnis
I have been experimenting with the relative setting of the G2 grids. The attached photo is with a low-brightness grey G2 setup (didn't upload for some reason; musta been too big. Substituted an ad c.u.). It is fairly decent and still viewable in the morning light. When a brighter grey is obtained with a relatively greater G2 setup, the resulting picture will lack adequate red phosphor output, an effect that is particularly noticeable where green is an element of the color being reproduced (as in that odd hue in the background of the GMA-set).

A low G2 grey setup provides greater G1 (control grid) response; a high G2 (brighter grey) setup delivers a brighter picture. With the greater G2 setup, I was able to watch the set during a bright sunny day with just the blinds closed.

So far, I haven’t been able to have it both ways.

Next step is to backup farther and readjust the red purity, which has deteriorated since set up weeks ago, as discovered last weekend during G2 adjustments. This will be at least part of the solution.

Now it would be real neat to design a circuit that would adjust black level and white balance for a 15GP22 in a similar fashion found in today's modern TV sets. During the blacker than black and peak white pulses within the blanking periods the gun current for red, blue, and green would be individually compared to a reference and then G1 and G2 adjustments made automatically!
Reply With Quote
  #79  
Old 12-14-2005, 09:22 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
Quote:
Originally Posted by Tom_Ryan
Now it would be real neat to design a circuit that would adjust black level and white balance for a 15GP22 in a similar fashion found in today's modern TV sets.
It would make an interesting project.

At this point, if you adjust the G2 for a lower gray and view the set in subdued light the CT-100 picture compares favorably with a digital set tuned to the same analog broadcast. There are differences of course: at those times when the digital set shows virtually no phosphor glow, the same area on the CT-100 screen will sometimes show a very dim glow.

On a similar note, I’m borrowing a virtual multimeter. Hope to be able to develop a data-logger-type monitor that will keep a txt file record of circuit voltage. I’d kinda like to learn something about how critical the 115-Vac line-voltage spec is to optimum CT-100 operation. If it works I’d particularly like to gather data on how the high voltage varies with line voltage.
Reply With Quote
  #80  
Old 06-19-2006, 04:59 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
The value of remanufacturing vintage parts...

The last of my three vertical convergence transformers failed. One is used in a CTC2, the CT-100 chassis. Sunday morning June 18, 2006, the fuse protecting the H-V cage blew on turn-on. Unlike my two other failed transformers, however, which still display correct dc resistance, this failure wiped out the secondary. The tap is completely open. There are about 12 Meg between the top and bottom of the secondary where about 12 k-ohms should be. This part has an extremely high failure rate. Probably second only to the 'white' peaking coils that rot open.

For the repair, I tacked in one of John Folsom’s newly manufactured replacements I've had for about a year now. It was static-tested at about 4 kV across primary-to-secondary for a few hours when it arrived last June, and so I expected a no-issue installation.

On the bench, the H-V ran a steady 21 kV with the new transformer in place and the H-V control set wide open with a 115-Vac line. The focus voltage, which passes through the secondary and is the reason for all the stress on the transformer, is steady at 3.5 to 4 kV, depending on the focus control position.

Picture is of the new transformer on the rear of the H-V cage.

In the future, I’ll remove the failed core from the transformer housing and use the original case around the new transformer.

Returned the chassis to the cabinet today, cranked the H-V control back to the specified 19.5 kV and while I haven’t reconverged it yet, it's perfectly watchable.
Attached Images
File Type: jpg CT-100-replace-converg-tra1.jpg (57.1 KB, 81 views)

Last edited by Pete Deksnis; 06-19-2006 at 08:48 PM.
Reply With Quote
Audiokarma
  #81  
Old 06-20-2006, 12:47 AM
kx250rider's Avatar
kx250rider kx250rider is offline
REAL TVs have TUBES!
 
Join Date: Oct 2005
Location: Los Angeles & Dallas
Posts: 3,239
Nice clean new-looking seleniums there, and may I add a nice clean chassis overall! Are those seleniums new? I've never had to change any on a CTC-2. On the subject of reproduced CT-100 stuff, has anyone made focus and convergence pots? I've had a couple of them with open convergence pots, and one with an arcing focus pot.

Charles
Reply With Quote
  #82  
Old 06-20-2006, 07:05 AM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
Quote:
Originally Posted by Kaye-Halbert TV
Nice clean new-looking seleniums there, and may I add a nice clean chassis overall! Are those seleniums new? I've never had to change any on a CTC-2. On the subject of reproduced CT-100 stuff, has anyone made focus and convergence pots?
Those selenium diodes are there for looks only; while I have not had a pair fail either, for safety they were replaced electrically with a couple of 1N4005’s.

As you know, the failure of a vertical convergence transformer is particularly insidious because a common failure mode causes a chain reaction that burns out the focus pot. Too much focus current is drawn if the secondary shorts to ground; the 1X2B focus rectifier plate goes cherry, and the pot can literally blister on the outside and melt internally.

While its design voltage rating is unknown to me, the focus pot is the center of a three-element voltage divider with nearly 4 kV at the wiper. While I haven’t had to do it yet, I’ve seen an ordinary linear taper pot successfully substituted for the original one. Personally, if I have to do that someday, I’ll make sure there’s an insulated knob on the shaft before I adjust it.

I had a pleasant surprise when the chassis came out of the cabinet. Notice in the picture the hue control -- the variable cap on the end of the center shaft of the three running back from the front panel. It's in the dead-center position. Exactly where it was after aligning the chrome AFC a year ago.
Reply With Quote
  #83  
Old 08-29-2006, 02:35 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
UPDATE to "The value of remanufacturing vintage parts..."

Finally got to perform a full convergence on the set two days ago, and the newly manufactured vertical convergence transformer is doing a fine job. The procedure improved convergence to the point where the overall 15GP22 image -- to use the vernacular of the streets -- looks sharp as a gnat's ass.

A minor inconvenience is the weather. Yesterday is the second time in recent history that a spell of humid weather affected the high voltage. Not certain where the damn humidity planted the unwanted load, but it's highly unlikely that the new transformer is a factor. The last time this happened was a week after replacing the transformer. A three-week hiatus with no power applied to the set brought it back: the high voltage recovered after the weather turned dry.

Last edited by Pete Deksnis; 08-29-2006 at 02:42 PM.
Reply With Quote
  #84  
Old 09-06-2006, 08:59 AM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
Re the low H-V problem...

What with the remnants of the hurricane passing through here recently, there's been so much rain the grass is so green it looks fake. So what better time to again check H-V under extended high-humidity conditions.

Last night I did it a little differently. With a 115-Vac line I pulled open the H-V lead then applied power. The H-V swung right up to 21 kV (about right for a CT-100 unloaded H-V supply) and stayed there.

Plugged the CRT back in and powered up again. Sure enough, after some mild frying the H-V settled at a slightly low 17.5 kV, but in a few minutes was back up to 19.5 kV.

I believe in my case the culprit is leakage from the flange; last year after restoration I had to remove and cleane the CRT and rubber insulator around the flange to arrest the same frying/leakage.

If you have to you have to. But not looking forward to pulling the CRT for another cleaning. Not so much for the work involved, but I don't like potentially messing up a satisfactory alignment.
Reply With Quote
  #85  
Old 09-06-2006, 12:38 PM
kx250rider's Avatar
kx250rider kx250rider is offline
REAL TVs have TUBES!
 
Join Date: Oct 2005
Location: Los Angeles & Dallas
Posts: 3,239
Quote:
Originally Posted by Pete Deksnis
What with the remnants of the hurricane passing through here recently, there's been so much rain the grass is so green it looks fake. So what better time to again check H-V under extended high-humidity conditions.

Last night I did it a little differently. With a 115-Vac line I pulled open the H-V lead then applied power. The H-V swung right up to 21 kV (about right for a CT-100 unloaded H-V supply) and stayed there.

Plugged the CRT back in and powered up again. Sure enough, after some mild frying the H-V settled at a slightly low 17.5 kV, but in a few minutes was back up to 19.5 kV.

I believe in my case the culprit is leakage from the flange; last year after restoration I had to remove and cleane the CRT and rubber insulator around the flange to arrest the same frying/leakage.

If you have to you have to. But not looking forward to pulling the CRT for another cleaning. Not so much for the work involved, but I don't like potentially messing up a satisfactory alignment.
I have run into humidity problems BIGTIME while working on TVs along the coast here in CA. That ocean humidity not only is wet, it's corrosive. It leaves a sticky white film on everything. The best solution, which I have done many times for customers, is to put a computer fan blowing across a small light bulb inside the cabinet 24 hrs/day. It works! The Mitsubishi big screens get very unhappy in the ocean breeze, and the arcing almost always gouges a channel in the glass from the anode holes to the nearest ground, ruining the CRTs

In the case of a CT-100, you could turn the bulb & fan on the day before you plan to run the set.

Charles
__________________
Collecting & restoring TVs in Los Angeles since age 10
Reply With Quote
Audiokarma
  #86  
Old 09-06-2006, 06:43 PM
dtuomi's Avatar
dtuomi dtuomi is offline
VideoKarma Member
 
Join Date: May 2006
Location: Thousand Oaks, CA
Posts: 231
Quote:
Originally Posted by kx250rider
I have run into humidity problems BIGTIME while working on TVs along the coast here in CA. That ocean humidity not only is wet, it's corrosive. It leaves a sticky white film on everything. The best solution, which I have done many times for customers, is to put a computer fan blowing across a small light bulb inside the cabinet 24 hrs/day. It works! The Mitsubishi big screens get very unhappy in the ocean breeze, and the arcing almost always gouges a channel in the glass from the anode holes to the nearest ground, ruining the CRTs
How close o the ocean are you? Or to rephrase the question, how far from the ocean do you have to be in Southern California before this isn't a problem?

David
Reply With Quote
  #87  
Old 09-07-2006, 03:03 AM
Tom_Ryan Tom_Ryan is offline
VideoKarma Member
 
Join Date: Dec 2005
Posts: 189
The light bulb/Fan trick basically raises the temp high enough to reduce condensate from forming on surfaces inside the TV. Another approach would be to place a tray of silica gel or drierite (CaSO4) inside the set for a day or so.

I'm 5 miles for the Ocean in San Diego. Even at this distance I'm careful about exposed high voltage anodes outside when the humidity > 60%. Of course, warm humid days and cool nights often leaves the air saturated causing dew to form on cooler surfaces - hence the possibility of arcing.
Reply With Quote
  #88  
Old 09-09-2006, 11:35 AM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
Humidity and what to do next...

For three days now the set has been working w/o H-V problems, but if/when it happens to lose adequate H-V due to weather/humidity again, I'll remount the CRT without the mu metal shield and H-V insulating wrap. Should help pinpoint just where the short is taking place.

Two or three times a year I get to climb up on the roof after a major storm and reorient my $10 antenna towards NYC again, like yesterday. See photo.

My humidity problem comes from the lake across the street, which runs three blocks down to the Atlantic ocean, which is of course the real culprit.
Attached Images
File Type: jpg ocean3blocksEast_crop2.jpg (75.7 KB, 38 views)
Reply With Quote
  #89  
Old 09-09-2006, 11:46 AM
Steve D.'s Avatar
Steve D. Steve D. is offline
VideoKarma Member
 
Join Date: Sep 2002
Location: Hollywood Hills, Ca.
Posts: 1,790
Hey Pete,

Certainly looks like state of the art equipment. I hope you're not using a $10.00 ladder to get up there. My brother swore he would kill me the next time I climbed on the roof to fool with an antenna. So either way there is risk involved.
Be careful.

-Steve D.
__________________
Please visit my CT-100, CTC-5, vintage color tv site:
http://www.wtv-zone.com/Stevetek/
Reply With Quote
  #90  
Old 09-09-2006, 01:01 PM
Pete Deksnis's Avatar
Pete Deksnis Pete Deksnis is offline
15GP22 demo @ ETF 2007
 
Join Date: Jan 2005
Location: Big Rapids, MI
Posts: 761
Quote:
Originally Posted by Steve D.
Hey Pete,

...either way there is risk involved. Be careful.

-Steve D.
You're right Steve, we seasoned guys have to step smart.

As Pierre Salinger quipped years ago, when quizzed by a reporter who asked if he were safe skating on a frozen pond:" I may be plucky, but I'm not stupid."

Actually, I had to crop the bejesus out of that cell picture to get it to load up into AudioKarma's guts (my access to Photoshop is temporarily down).

The full frame shows a flat roof. Plus there's an easy-access hatch from the third floor ceiling, with a built-in wall ladder. My son was up there too to keep an eye on the old man.

[Fodder for conspiracy theory threads. Much later, Salinger, press secretary to presidents Kennedy and Johnson, got into hot water in '96 for publicly arguing that it was not a 'spark' in a fuel tank that brought down TWA flight 800... ]
Reply With Quote
Audiokarma
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 08:59 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.