Another local Hoffman! COLOR!
 

Found a Hoffman colorcaster television local.

don't have it yet

http://suzaku.live-evil.org/hoff112.jpg
1967 w a 23EGP22 CRT
:D

looks at the SAMS folder...

This thing is an RCA clone! :scratch2:

...with a Zenith picture tube!

Yes, it does look like a Zenith type cataract, but the sticker on the back says sylvania, did they use the Zenith method?

http://suzaku.live-evil.org/zenuth.jpg

Zenith didn't make a 23EGP.

BTW, what's the "Zenith method"?

Sylvania CRTs do get Zenith style cataracts, and supposedly respond to the same removal methods. The only Sylvania color CRT I've had was a post safety glass tension banded tube so I've never verified what I have read that they respond the same.

From what I have seen here and there, there are only 2 major types of methods (styles) of bonded safety glass used in these things, RCA, which turns white & cloudy (moldy) looking, best removed with heat, and the Zenith type of bond, which turns green and gummy, best removed with thin wire, and a lot of patience and strong hands! :)

As E.M. Has confirmed, this tube does indeed have the Zenith type of bonding used for the safety glass, meaning it will be much harder, and not to mention hazardous than the RCA 21FJP22 ones I have done before.
As I have heard that these tend to be more unstable in the process than the roundies, :(

I'd call it mid-level danger. The 23EGPs with RCA style cataracts tend to implode when heated worse than round or later rectangular tubes. The Zenith guitar string method has has a 100% success rate for me on the yellow/green cataracts, and doesn't use heat.

If you remove the cataract with heat it'll probably implode. If you remove it with just guitar string it'll probably be fine, but a raw 23EGP has a slightly higher implosion risk just sitting there than other color tubes.

I have an RCA-style (moldy white crap) cataract on a 23EGP22 in an Admiral combo.

Tom: it sounds like no heat is safest, maybe even baking it in sunlight is a risk. The guitar string may need to be heated ala current source?

I have been looking at the SAMS for a while now, and just LOLing! :)
It's obviously an RCA CTC-17 -ish type clone, with mods, but what got me was the totally pointless mod of what is called the “color caster” color indicator circuit, which is 2 NPN transistors hooked to the color bandpass, which turns on 3 lights when color is present.... WHY BOTHER? :O


HEY, WE HAVE COLOR! let's light up the color, and tint controls! :D

Well, hypothetically, the color could be turned all the way down accidentally by kids or even the supposedly intelligent owner.

Of course, in later years we had cable systems that never turned the color burst off on anything including black and white movies, producing crosscolor when it should have been killed. By then no sets had a color indicator, but it would have been useful to me after I turned the color down deliberately on black and white movies.

Edit: well, not really useful, as it would always indicate color, but it might remind me to turn the color up again.

1 is good, 2 is a charm, 3 is nuts! :P

http://suzaku.live-evil.org/crazy-color.jpg

Wow - they even had a color defeat switch. This would make the indicators useful as the user might have turned the color off with the defeat switch.

The reason for a color defeat switch was for cases where a set was used in a fringe area and the noise might have made the color killer unreliable. The color killer control could be set to make sure color programs got through, but the switch could be used to eliminate color snow on black and white programs without disturbing the color control setting. Obviously the color killer and color indicator could have different thresholds. I wonder if the color indicator tended towards false positives or false negatives under noisy conditions.

I always thought the color defeat switches on the various brands were to eliminate color on fringe color programs where the picture looked worse in color with snow than without color.

What gets me is the 3 parallel lights, " Easy vision cinema " Say what? :scratch2::D

Well, that seems to be a pointless gimmick! :D
http://suzaku.live-evil.org/pointless.jpg
a 2nd CRT bias? and up front where the user can set it? :O
wow...

Mind boggled...
To me it seems that adding that gimmick just gives a faster way to wear out the green/blue guns, having a master CRT bias pot on the back tied to the cathodes of the Y-AMPS, and another on the front, on the CRT green/blue G1 that the user can set?

This is prob why it was replaced with a new one in 1973.
No telling what condition it's in now, won't know till I pick it up on Saturday. :o

This philosophy might be followed by an engineer, but you can bet that the average owner would want that expensive color set to show even noisy color if it was available.

It may have been the pot equivalent of the sepia switch om my old airline console. The idea was that on B&W films and TV shows older viewers that watched film before TV existed may prefer the look of sepia monochrome film stock and wish for a way that their TV could duplicate it...It looks stupid on color shows but I can see why some people might like it on monochrome shows.

The Easy Vision Cinema doesn't affect drive levels, only tracking. Not sure of the visual effect with this hookup, but probably a variation between sepia, neutral and bluish shadows.

Some Motorola sets had this third color control (they called it Tint, and called the phase control Hue, rather than Tint, as RCA and everyone else did). In the Motorolas, it was actually useful if the viewer knew how to use it (which nobody did), because the DC coupled Motorola single tube demods tracking would change depending on the mismatching of the tube sections. In the cheaper models, the control was replaced with fixed resistors, and if you replaced the demod tube, you may have needed to adjust G2s to get neutral tracking again. The early rectangular high end Magnavoxes had an automatic color switch (with a fancier name I can't recall) that reduced green-purple color saturation and set the tracking to sepia. It reduced the variation on skin tones, but gave the "tan cowboy on a brown horse riding into an orange sunset" kind of picture.

Of course, if the color AFC section was crappy and couldn't maintain lock under noisy conditions, that would certainly make you want to turn it off.

I had never seen an adjustment like that before in a vintage TV, they must be rare, I have seen things like “color temperature settings” in LCD types, but in all the years since HS till now, this is the first time I have seen one in a tube type tv. :O

The color temp setting in an LCD should not affect the tracking (that is, making shadow color different from highlight color) - it shouild be more like the drive settings in a CRT.

Note that with the excellent tracking stability of modern digital video hardware, deliberate separately controlled mistracking of highlights, midtones, and shadows is used in cinema and now even in Photoshop still image processing, where it is termed "color grading." It can be effective for setting a visual mood, but can also lead to fads like the strong orange-cyan look of some movies.

So this basically allows the watcher to alter the balance points of the color demodulation G/B on the fly to adjust to the viewer's tastes? Fancy!

Or as an old Zenith engineer once said when shown the first RCA experimental color TVs, "27 controls, each one making it worse!"

And yet, with all the “perfection” of ATSC,etc, it seems that the color still isn't always consistent. Go figure.

Almost The Same Color?

Not the fault of the ATSC system, which does not deal with color except to transmit the bits.

If this were Reddit we'd have 100 Europeans piling in right now to insist that PAL is vastly better at color, and that NO their TVs most certainly do not flicker!

UPDATE!

I got it!!

VERY bad news , CRT is damaged!
pin 12 has been broken off of the base, this is prob why they dumped the set.

http://suzaku.live-evil.org/0716221359a.jpg
http://suzaku.live-evil.org/0716221403.jpg

good news is, I may have been able to fix it by tacking a wire to it.
http://suzaku.live-evil.org/0716221404.jpg

flyback looks OK

now I gotta start bringing back to life

one very dirty looking RCA type looking chassis.

http://suzaku.live-evil.org/0716221748.jpg
http://suzaku.live-evil.org/0716221746a.jpg

Progress, and step back, sort of? :O

After seeing the broken pin on the 25AP22A ( or so the sticker on it says ) , and not knowing if my fix attempt will work or not. I tried to bring the set slow up on Variac, this fond that C3 was REALLY bad, as it got hot VERY fast.

So I replaced all the sections of it, and tried again, THIS time power came up, I got hiss in the speaker, I heard vert start, but NO HV....

looked inside the HV cage, the HV rect was lit, and very hot. Pulled the cap off and got a good strong AC arc all over the place, removed the HV shunt, no change,,, BAD 3A3A, of which I have no spares.

so now, before I can make sure the CRT is any good, I must wait for the new 3A3C to get here so I can get HV up. :(

OK...
It was NOT a bad 3A3A :O

http://suzaku.live-evil.org/0717221006a.jpg

had a burn out in the heater wire FOR it,,,,

crispy carbon!

http://suzaku.live-evil.org/0717221025.jpg

after the repair

Yikes. Hopefully that arcing and high current didn't hurt the rect of worse the fly.

The Fly is OK, the way i found it was, I used a handful of 20KV 5mA HV High Voltage Rectifiers i had, doubled up on them so they would not fry.
but quickly found that when NOT hooked in circuit i had 25k HV, but they would burn up as soon as I tried to wire them into the normal way.

that is how i found 1he 5m to ground short on the heater winding for the rect tube and went to look for the problem.

When I looked at the two pictures of the chassis out of the cabinet, I noticed that there were two transformer cans with a piece of black tape over the top adjustment hole. Any idea why they were covered? Was it a way of the manufacturer to discourage "diddlers" from adjusting these cores?

Curious. Can't think of a reason offhand. Possible that someone who worked on it did that?

What circuit are the taped cans in?

For relatively low frequency circuits where the stray capacitance is not significant, it would be possible to include a capacitor inside the coil assembly and automatically pre-tune it during the assembly manufacture, before installing on the printed circuit.

Motorola's coil plant made some pre-tuned assemblies, but I always thought they still had to be adjusted after installation in the chassis. I used eight pretuned coils (IIRC) in our redesign of the CBS video film player (EVR), at frequencies around 900 KHz and 1.8 MHz, [linear-phase chroma pilot and chroma subcarrier filters] but they definitely had to be touched up in the final product. This was due to the differences in strays between the winding machine and the final product. It would have been possible to tune samples in the final product and then have the winding machine duplicate the tuning, but it was not worth it because the printed circuit might be changed at some time (material or layout) and change the strays.

no idea why it's like that :o

Good news is, the HV rect is OK!
bad news is, my patchwork did not hold.
the HV blasted through / around the heat shrink tubing and found a path to grd and arced again, I guess i should not have clipped it down

now time for more drastic measures.

http://suzaku.live-evil.org/0717221306.jpg

huge piece of tubing filled with silicone
this will take many hours to cure
and If it's dry enough to put pack together late tonight, I will slop more on it.

hope to be ready to power it again mon night.

using this stuff
https://webaps.ellsworth.com/edl/Act...05&language=en

I am really hoping this CRT is going to work, otherwise things will really suck pretty fast T_T