Another Project?

[leadlike]

I found the problem-the choke after the rectifier is open. AAAAHHHH!!! Anyway, I have a few that will meet the current rating, but none that have as much resistance or inductance as the original (500 ohm, 7H). I think I'll have to make a run to storage and pull my T-120 chassis and see if that choke will be a good match.

I found that when I disconnected the bad choke, some voltages went down, while others went up. It must have been loading things down. I'll have a better idea once I get a new choke in.

[leadlike]

A little light at the end of a very dark tunnel....B+ is a few volts low, B++ is dead on. The flyback (although this is an iron core transformer, so is this still a flyback?) is putting out just under 10kv, the schematic calls for 8.3kv. Vertical is shrunken, but the controls are very dirty...perhaps a deoxit will clear all of that up.


GEDC0139.jpg

[bandersen]

Awesome It's great to see that CRT glowing!

[leadlike]

I just can't seem to get anywhere with this set. The Phono section seems to be working (though I would need the proper phono cartridge to be sure). The AM radio performs superbly, but I cannot get anything on FM, or audio or video on any of the television settings.

All of the voltages are in line as they should be, but I just don't own any television alignment equipment except for a color bar generator. I can inject audio and video through all of the stages, but when I try to inject any rf into any stage, I barely get anything-probably just swamping the receiver, as I get this same weak signal on all channels.

I have added all new tubes into the rf/if sections, cleaned the tube sockets, cleaned all of the controls, and measured continuity across all coils. I just have no clue where to go from here-save for adding a/v jacks and bypassing the tuner entirely.

[Jeffhs]

I'm curious. If the present owner of this TV already has a modern flat-panel set he wants to put on top of the cabinet, what would he need the original TV for? The only thing I can come up with is that he may want to feed the audio from his home theater setup through the original TV's sound channels, but that doesn't make much if any sense since all home theater receivers have outputs for multiple speakers (some as many as seven, counting subwoofers).

Also, there is the problem of power line isolation. I personally wouldn't try to use a 70-year-old TV with any audio system having solid-state components, unless I were sure beyond the shadow of even the most unreasonable doubt that the isolation capacitors were good--most such caps in unrestored sets of this age all but certainly failed years or decades ago, and cannot be trusted. Even if the original isolation networks were replaced with new components, I would still be leery of such things as ground loops or voltage on the chassis of the modern device.

[leadlike]

Jeff,

The owner's ideal plan would be to use the set to watch B&W films on a few times a month. The flat panel would be the "daily driver" for all of his other programming.

They would be hooked up separately, sharing a cable box (a/v outputs going to the flat panel, coax out going to an rf modulator for the GE). If I did have to add a/v inputs, you can be sure that even though the coupling caps are all replaced, I would still add a cap to the inputs, to further isolate any solid state gear that could be feeding it.

A few neat items on circuit design in this set:

I found the plate voltages to be 50v too high on all of the video IFs. It turns out that the contrast control is actually a gain control. As you adjust the contrast, you can alter the plate voltage of all IF sections by about 60v or so.

The vertical and horizontal hold controls are in the rear of the set. The literature I have been reading on this set describes these controls as something that only need be set up once, and then left alone. We'll see how much that is true once the set it running. I will say that the vertical height, hold, and linearity interact with each other a good deal. If that vertical hold control was on the front of the set, in the hands of the average Joe, you could probably really mess up the picture.

[Phil Nelson]

Originally Posted by leadlike

the contrast control is actually a gain control

The RCA 630TS has a manual gain control in front, labeled Picture control. Kinda weird until you get used to it.

Originally Posted by leadlike

The vertical and horizontal hold controls are in the rear of the set.

My DuMont RA-103 is the same. I was initially dubious, thinking the designers were just a bunch of showoffs. Turns out that the horizontal and vertical are absolutely solid, even with different video sources, changing channels, etc. None of my other restored TVs has that kind of stability.

By the way, did you ever clean the contacts in the tuner?

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[jeyurkon]

Originally Posted by leadlike

The vertical and horizontal hold controls are in the rear of the set. The literature I have been reading on this set describes these controls as something that only need be set up once, and then left alone. We'll see how much that is true once the set it running. I will say that the vertical height, hold, and linearity interact with each other a good deal. If that vertical hold control was on the front of the set, in the hands of the average Joe, you could probably really mess up the picture.

On my 1-108 chassis Sylvania the horizontal and vertical controls are underneath the chassis. Accessible, but not easily. Once set, they are very stable. The horizontal circuit is an RCA design.

John

[leadlike]

This thing has pretty well killed my resolve to work on televisions. I have never done so much work to get so little done on a television. Where I stand with this thing now is that the am radio only works, and I get only a very silent white noise sound for audio on FM and television. I get a raster, but no image on the screen. I've tested all of the components I can get to, and I have replaced all of the questionable parts, and put in a new lineup of tubes in the receiving/IF sections with no changes.

Trying to inject signals into the set, but my B&K analyst is just too iffy to get any results. I've been scouring ebay for a sweep generator and marker generator, but I've been outbid on all of this gear for the last month.

I'm pretty sure this set is out of alignment, as many of the circuit adjustment screws that were sealed in blue locktite have clearly been fooled with. If anyone in southeast PA has the appropriate alignment equipment that could be used to analyze this set, I'd love to see what it's issues are.

Failing that, is it possible to simply put a/v jacks into this? Here is a schematic for the 801, which has nearly identical audio/video output sections. If someone is aware of how to properly do this, I would like to know how.

http://www.one-electron.com/FC_Radio.html

All that aside, here is some of what I did do:
GEDC0166.jpg

GEDC0165.jpg

Here it is, the power supply for this set. Using a transformer for an RCA 12" set, a Crest power transformer, and some surplus transformer, I had enough to power the tv. It is mounted to a cake pan, and all routed out to a European-style terminal strip. You can also note the two Dale-type power resistors mounted to the angular heat sink on the top of the power supply. The whole thing weighs 35 pounds. I am still very happy that I was able to create something like this, but I need some way to continue to move forward with this set.

[bandersen]

Nice job on the PS

Is you BK working well enough to inject video at the grid of the video amp (V7) ? That should allow you to get the sync circuits working and see an image. I believe you could inject a composite video signal here too for your A/V jack, but you'd need to play around with the level and polarity.

As for audio, you can add a jack at C41 on the volume control for AUX. Maybe replace that 2 position TEL / RAD switch with a 3 position one

[leadlike]

GEDC0167.JPG

Here is the kind of scrambled video I get when I feed in video from my B&K, my color bar generator, or even my dvd player into the grid of the video output tube. I can't sync anything. I'm just feeding this in with bare leads. Should there be a coupling cap, a diode (since this is past the video detector diode) or anything else needed to properly couple the signal to the tv?

I can't even tell if there is even a video image to pull from this. I just simply go from a flat grey raster to this mess when I feed anything in. Adjusting the output levels on the B&K does nothing but fade to picture to snow.

[bandersen]

That looks promising to me - you just need some horizontal sync. It should fade to snow as you drop the level. Have you tried flipping the polarity switch on the B&K ? Do the horizontal clipper, amp, discriminator, etc. circuits check out OK ?

Yeah, I'd use a coupling cap so as not to damage the video source. Maybe a few 100 pF. You don't need a diode if you're feeding in a composite signal.

[jeyurkon]

I'm not familiar with the set, but it looks like the horizontal frequency is way off. Have you tried to adjust the horizontal hold?

John

[leadlike]

Okay, after fiddling around with the horiz. sync on the television, it just mustn't be syncing on the Horizontal. The best I can do is get it to "lock" on a multiple of 8 repeated horizontal images of the B&K test pattern. Flipping the B&K's polarity switch makes the image go negative.

I've checked every single component in the horizontal output circuit, and I guess I'll start working my way back to the sync clipper, etc. Tomorrow night.

With the video if circuits working away, could that possible swamp the B&K's signal, considering the contrast control is a really a B+ gain control for the IF strip?

[Jeffhs]

Did you try adjusting the horizontal hold control? I agree with bandersen that all your set's picture needs is sync, and yours is way off. I'd try adjusting the control first, before pulling the chassis. That failing, I'd check the horizontal AFC, as it may be yanking the oscillator so far off frequency that even the hold control won't bring it back.