Another local Hoffman! COLOR!

[Yamamaya42]

Originally Posted by Jeffhs

I have a question in regard to your Hoffman Colorcaster TV. I looked at the photo of the service adjustments for this set (of which there must have been twenty or more, as I would expect in a 1956 color TV) and saw, to my surprise, a brightness control. My question is this: Why would the brightness control be located on a control panel which has mostly service adjustments, which of course are not to be touched by anyone other than a qualified service technician? Or was there another brightness control wired in parallel with it, the second control being the user brightness adjustment?

In any case, I would think two brightness controls would be one too many for any TV, color or b&w. I could understand this if the second brightness control has a definite function, such as setting the maximum range of the user's control, but otherwise I am at a complete loss to explain this. Most later color sets (late 1960s on) had only one brightness control. Was there something about 1950s color televisions which actually required the sets to have two brightness controls, or was the second control used, as I said, to limit the range of the user's brightness control?

Thank you for any and all information on this, as this TV is the first one I have ever seen (I have never seen a Hoffman TV in person) with a brightness control on a panel normally reserved for service adjustments. I also saw a few other controls on this TV's service control panel which are ordinarily service adjustments only, again to be adjusted only by qualified service technicians. Were these controls wired in such a way as to limit the range of the existing controls? If so, as I said, this is overkill of the worst sort, as most later color sets only had one control for most service adjustments. These controls almost certainly would not be noticed (and should not have been) by the average color TV set owner, anyway, as many color TVs of the '50s and even into the early 1960s had a warning label pasted somewhere on the inside of the TV cabinet, to the effect that service adjustments, tubes and other parts of the set must not be touched except by a qualified TV service technician.

I'm not sure which docs you saw, but this set has only one true brightness control, however I have seen a “ sub- brightness” on some sets, perhaps that's what you saw?

SAMS does list a potentiometer on this to set kinescope bias, but this chassis has a switch for that.
This I can only attribute to the SAMS being for a Hoffman MO# MS-7322 and seems I have a MS-7322 (B), and this one SAMS is the only one there is, and it's close enough.

[old_tv_nut]

Sets with an "automatic" color switch of some kind would switch in a set of factory preset controls. Is that the case here?

[Yamamaya42]

Not sure, but this thing does seem to be a weirdly modded CTC-15 more than a 17, as I believe the 17 used a 1V2 or the like for focus, and this has SS like the CTC-15.

What ever it is, it does seem to be a Frankenstein creation! A little bit of this, a little bit of that, put into a pretty unique package!

[Yamamaya42]

AHHHH! That explains the odd behavior I saw last night!

Turns out that what is stamped out in the back of the chassis for the controls is NOT what they really are, they had stickers to show what they were, but they are long gone, what was marked as CRT bias was really VIDEO PEAKING, which was set in top most setting, and I sort of freaked when I changed it and lost picture and just got a blank raster.

Meaning there may be bad caps or more likely bad resistors, or the switch itself is dirty.

The REAL CRT bias adjustment is indeed a potentiometer, just as the SAMS says, but in a position stamped for something other than CRT bias, and when checked, much to my relief, it was turned 1/3 the way up when it made the video posted yesterday!

[old_tv_nut]

Originally Posted by Yamamaya42

...
Turns out that what is stamped out in the back of the chassis for the controls is NOT what they really are...

Sheesh!
You are now officially a member of the guild of electronic archeologists!

[Electronic M]

Wow... I've been steered that wrong by Sam's before, but I don't think I've been lied to by chassis stampings... That's some 50s B horror movie level cheapness to fix stampings with stickers.

[Yamamaya42]

I did find ONE of the stickers that fell off, for top/bottom pincushion.
I did manage to clean up the convergence a bit, will make one more vid before I yank the chassis to haul upstairs to go over it with a fine tooth comb looking for out of spec parts.

It's looking rather well considering it's just been patched together and I did not put the blue lateral/purity assy back on yet.

The whole thing is just too big to bring upstairs, but at least they made it easy to unplug / reconnect the tuner / front controls, just 2 plugs & the IF.

[Yamamaya42]

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

2nd video

[consoleguy67]

Looks a lot better!

[Yamamaya42]

So far, I have been over 1/3 of the color PCB and i have not found one out of tol resistor yet of the ones the I CAN test w/o removing them from circuit, starting to think that it's not worth checking them at this point any more :O

[Yamamaya42]

Recapping 1/2 done (electrolytic)

http://suzaku.live-evil.org/0724220102.jpg

[Electronic M]

Originally Posted by Yamamaya42

Recapping 1/2 done (electrolytic)

http://suzaku.live-evil.org/0724220102.jpg

BTW you can embed that picture link so the forum displays it as a picture (the only reason I didn't is the resolution is so high it makes the text too small to read if zoomed out enough to see the whole pic....a lower resolution say 800x600 or 1080HD source image at the URL would fix that).

All you need to do is type this [IMG]linkURL[/IMG] or in the "go advanced" reply page click the square that looks like it has mountains and a sun in it and it will automatically give you the [IMG] BB code.

I've been using Flickr and they give me an over complicated BB code to copy paste that I usually end up editing down so I can arrange my pictures in a neat grid.

[Electronic M]

Whenever I get a set that someone has converted to LED lamps I reflexively then switch it back to incandescent it's one of those things that gets under my skin about as bad as a set that someone painted some random ugly color.
I'm pretty well stocked with bulbs thanks to an estate sale of a mid-century EE who had 2 mason jars of spares, but when I use that up I plan to hit up rockauto...When I was doing my 6V 1947 Oldsmobile I had a look at every part they had and found a number of radio bulbs it used for the interior lights were DIRT cheap compared to mouser, and better than bob's capacitor who was my supplier before the estate sale. I think if I browse around 40s cars on rockauto enough I should find almost everything I typically need for consumer electronics.

[Yamamaya42]

I really don't mind using LEDs at all, they are cheaper than bulbs, and outlast them.

On second thought, since the source is 6.3v, and the drop across the transistor is pretty much nothing, w/o any bulbs, the switched on output should be about 6-7v so by adding a dropping resistor to ground, like 6-7 ohms should get me the 3.1v needed to use the ultra bright white LEDs, like I used in the GE TV.

Will just have to play till I find the right resistor value.

[old_tv_nut]

Originally Posted by Yamamaya42

I really don't mind using LEDs at all, they are cheaper than bulbs, and outlast them.

On second thought, since the source is 6.3v, and the drop across the transistor is pretty much nothing, w/o any bulbs, the switched on output should be about 6-7v so by adding a dropping resistor to ground, like 6-7 ohms should get me the 3.1v needed to use the ultra bright white LEDs, like I used in the GE TV.

Will just have to play till I find the right resistor value.

Trying to picture this. Wouldn't a separate series resistor for each LED make more sense?