This is the one I bought from captainmoody and hauled all the way from Michigan. After using it for a few months the color went out and the picture started waving back and forth the way it does when the power supply filter caps start going out. It sat for about a year and I just got back to it last week. I checked all the tubes, only found a few weak IF tubes, and audio amp tube. Then I just replaced all the electrolytics and hoped for the best. Fired it up yesterday and it worked just fine.

But then I turned it on today to find I could only get a b/w picture. First I tried turning down the color killer, but it had no effect. This set originally came with orange drops, so I wasn't expecting a bad cap, I knew all the tubes were good because I just tested them. I'm not that familiar with color circuits, but I figured the problem had to be in a section that would effect all 3 colors, so I started testing resistors around the chroma bandpass amp, found a bad one, changed it, and then I had color again.

But then if I turned it off and let it sit for at least 10-15 minutes, then turned it back on, it would take a few minutes or so after the picture came up to see any color but green. But after that all 3 colors would be on consistently and the set would work fine. Then I switched the G-Y amp tube with the R-Y/ B-Y amp tube, let it sit for 30 min and turned it back on, and there was no difference, it was still all green for the first few minutes it was on. Then I pulled the chassis and resoldered the wire from the 400v supply to the R-Y / B-Y amp tube, then when I turned it on it was all green for only about 1 minute, then the other colors came in. An improvement, but something still might not be totally right.

This set uses the same chassis as the CTC-15, with Philco's own tuner, which I think is nicer than the RCA unit because it unplugs so you don't have to carry it around with the chassis when you pull it. The stereo and amp are also Philco's own design. I'm recapping it now, just as a preventitive measure. It is unusual in that it uses 3 output transformers, one feeding a center channel. The right and left each feed a single 4" speaker. While two 10" speakers (one on each side of the cabinet) are connected in series to the center channel transformer.

OOOO! The much discussed Bewitched Zenith.

Nice Philco. Good to see it working.

polaraman

A great set you have...plenty of character!

My RCA CTC-15 had some goofiness in the color. It would be out of sync (barberpolling) which I could make better with adjustments but it wouldn't quite go away. I found that it would improve as the set played and after about 5 minutes it would lock. Each time I used the set it would lock a little bit quicker. Finally it would stay locked all the time and, knock wood, it hasn't given any trouble for quite some time now. I don't know...moisture built up in the coils that had to be "baked out"? Hard to come up with many ways something could cure itself.

All that stuff I did yesterday that I thought fixed this, didn't. Now the only color I'm getting is green, even if I let the set warm up for a while. And it's not that the blue and red guns don't work at all, because I can get a good b/w picture, just not a color picture with anything but white and green. I also get a good red, green, and blue horizontal line when I flip the service switch. Now according to the schematic down below, the voltage at the plate of the burst amp tube should be 50v, I have 400v. Is that a misprint or is it supposed to be 50v? If it is supposed to be 50v and not 400v, I can't find any components in that area that are bad that could be causing that. Now the 6EW6 is definetly good (and I tried another one too), but if I remove the tube while the set is running, there is no difference in the picture whatsoever. And the tint control has no effect as well. Any thoughts?

Try adjusting the color intensity control...if the chroma signal channel is working you will be able to vary the picture from straight black and white at the minimum of the control to a purple or green hue at the maximum.
You will need the 3.58 mhz oscillator signal to get actual colors and the burst signal to get it in sync.
If you have a scope I would check out the signal at the 3.58 mhz oscillator tube and see if a signal is being produced. Check the grid of the 3.58 mhz oscillator section and check the negative voltage against the schematic. As I remember you should have about -7 volts if the tube is oscilating.
Also check out the 6JU8 phase detector circuit if the set uses this tube.
If the 6EW6 plate voltage is high this means the tube is not drawing current...check for open components in cathode circuit and that the screen voltage is normal.

Working again.

The plate voltage at the 6EW6 is supposed to be 400v, and not 50, I checked it against another schematic and then I checked it again after the set was working (the 50v must be a misprint). The screen voltages and grid voltages were a bit low, but not by much.

The color intensity control would cause it to go from a b/w picture to a b/w and green picture.

The voltages at the 6JU8 phase detector would vary from 20 to 40. When I checked it the set would loose color sync all together and have the horiz color lines, but when I removed the meter it would go back to white and green.

Anything hooked to the 265v source tested about 30v low.

I replaced several resistors that were 10-20% off, but it made no difference.

Finally, not being able to find the source of my troubles, but pretty sure it did have to do with the color sync circuits, I hauled the scope behind the set and tested the 3.58mhz oscillator. I was getting a signal, I was trying to figure out if the frequency was right or not, then I just decided to try to hook the probe to one of the leads going to the crystal, and see what I got, then when I looked at the picture on the screen (the set not the scope) the color was back. I removed the scope probe, not working again. I tried just clipping a wire where I had the probe, and it still worked. I resoldered the crystal to the board, and that was all it needed.

A different Bewitched Zenith...

Put the stereo section back in today, this one blows away the Magnavox I was working on about a month ago. The dials on this unit light up, it looks great in the dark. I tried to take a pic where it could be seen, but it didn't come out that great.

Wow Adam, very nice. :) Seeing your Philco up and working makes me want to tackle mine again.

Finally, not being able to find the source of my troubles, but pretty sure it did have to do with the color sync circuits, I hauled the scope behind the set and tested the 3.58mhz oscillator. I was getting a signal, I was trying to figure out if the frequency was right or not, then I just decided to try to hook the probe to one of the leads going to the crystal, and see what I got, then when I looked at the picture on the screen (the set not the scope) the color was back. I removed the scope probe, not working again. I tried just clipping a wire where I had the probe, and it still worked. I resoldered the crystal to the board, and that was all it needed.


Modern scope probes have about 10pF of capacitence, so a 10pF cap to ground might be what you needed.

After working for about 2 days after I resoldered the crystal, I got the white and green picture again tonight. So I pulled the chassis and resoldered it again. I also did try a 24pf cap to ground (the closest I had to 10pf), but with the cap it had no color sync at all, then after I removed it, the re-resoldering of the crystal must have done something, as the color worked again. If the color doesn't stay this time I'll try picking up a 10pf cap. The side of the crystal that hooks to pin 3 of the 6GH8 already has a 82pf cap to ground, but it was only the other side of the crystal going to pin 1 of the 6GH8 to which hooking the scope probe fixed the color.

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I don't have any spare crystals, otherwise I would have tried changing it by now. Are replacements still available, if so where can you get them? From now on, I'm pulling them off of sets I junk, in the past year I junked at least 2 sets I knew had a good one. Are they interchangeable with newer sets, if so I can just drive around until I find one on the curb.

Another thing I just did was to exchange the slightly weak 6JH6 1st IF tube I was using (it was the best 6JH6 I could dig up), with a really good testing 6BZ6 (the schematic calls for a 6JH6). While the overall reception did improve with the better testing 6BZ6, but I doubt it had anything to do with my color problems.

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Well today I turned the Philco on and had the white and green picture again, so I pulled the crystal off a NOS chromacolor II era Zenith board I had, put it in the Philco. I still had the green and white, then I tried exhcanging the 6GH8 (even though the one in there tested good), no difference.

Next I put 3 24pf caps in series to get 8pf to ground from pin 1 of the 6GH8 (the plate of the chroma reference oscillator control) and it worked. As soon as I disconnected the caps from ground, it ceased to work. I tried this several times over a period of about 10 minutes and it was always the same.
But like I said before with 1 24pf cap it had no color sync. With 2 24pf caps in series it was not consitent, sometimes good color, sometimes no color sync.
Next I'll pick up an 8pf cap and solder it in permanently and see what happens.

This has to be the strangest tv problem I've come across yet....

Color came right up today, didn't take any time at all or any fooling with the fine tuning for the color to come up like before even on a weak station, so I think this extra 8pf cap might have done it.


Wow Adam, very nice. :) Seeing your Philco up and working makes me want to tackle mine again.

What year Philco? I've seen later round color Philcos than this where Philco used their own chassis instead of duplictaing the RCA, but never seen an earlier one than this ctc-15 model. I wonder what the first Philco roundie was...

Adam -

What a nice set - looks like you've got a lot of work in on it.

Maybe a long shot, but does moving the 6GH8 or any of the other color-related tubes around in the sockets slightly affect the color at all?

After I got my Admiral console running again, I had no color/weak/strange color. After working with it for a while, I noticed the color coming and going when I would wiggle the bandpass amplifier tube. Cleaning the tube socket and pins provided a good strong color picture all the time.

Jim

I am not sure adding a cap is the right thing to do. Yes it makes it work, but consider this, at one time the set worked without the cap. You might want to do some more troubleshooting before you call this one fixed. Start by checking the simple things, like tube shields, tube sockets, and especially ground connections. Be sure to resolder all the grounds where the circuit board connects to the chassis. These can cause some strange intermittent problems. Double check all the voltage and resistance readings, and you may need to get the scope out when it is acting up to find out what the problem really is. Just a thought.
Bill R.

Shaking all the tubes was one of the first things I tried, it doesn't do anything here. Also already tried exchanging several tubes even if they tested good, different sheilds on the 6GH8, and resoldered the ground connections on the color board.

The only 2 things that ever made a difference were resoldering the crystal (which only lasted for a short time), and adding this cap which seems to work permanently. I know my problem isn't the crystal itself because I changed it with a new one and no effect. Now there are a couple caps at the same junction point as the crystal (the pin 1 of the 6GH8 side of the crystal, which is the only one on which resoldering made a difference), C127 and C131, which may have been also affected when I was resoldering the crystal, I am going to try replacing those as well. Any resistors on the color board I've already checked and replaced if they were near 10% or more off.

I am not sure adding a cap is the right thing to do. Yes it makes it work, but consider this, at one time the set worked without the cap.

If it's a new or replacement crystal, it may have a different characteristic, and that the manufacturer intended it to have different capicitive loading. Crystals come in different flavors, paralle or series resonant, and so on. So the extra cap may be called for.

Have you gone through the chroma oscillator alignment procedure? It's fairly simple. Whatever does not respond properly will usually point to the trouble. It does not require a scope or any test equipment.

If it's a new or replacement crystal, it may have a different characteristic, and that the manufacturer intended it to have different capicitive loading. Crystals come in different flavors, paralle or series resonant, and so on. So the extra cap may be called for.

This is very possible since the replacement came from a much newer set. You just want to be sure everything else is as it should be to avoid any future problems.

Bill R

Next I changed that 4pf capacitor (C127), and all I got afterwards was a b/w (not white/green like before) picture. After a while, I found a 4pf cap to ground rather than an 8pf cap would bring the color back. I was curious what would happen with the old crystal (which I don't think was the original one either), so I swapped them back. With the old crystal, I got either a white/green picture (never just b/w like with the new crystal) without 4pf to ground, or good color with it.

Last night I went through the color allignment procedure that was in the sams, first time I ever tried that so I was worried I would make it worse, but it worked, and I managed to get it to work without the extra cap. It still works today, so I think this might be a permanent fix. I also went through the part of the allignment which centers the tint control, which is nice, because before it had to be all the way over to one side. However, after the allignment, shaking the 6GH8 does cause the color to loose sync, but if I just let it be it works. I might still resolder all the pins on that tube socket though. Thanks for all the suggestions... And what is generally used to adjust these coils?, I couldn't use regular tools I had because they were all made of metal, and was looking around for something non-conductive to stick down there, and finally managed to cut some chop sticks so they would work, but I would like to get something a little better.

There are (were?) non-metallic "diddle sticks" (adjustment tools) available. Since I haven't needed to buy one in decades, I'm not sure where to look for them.

A warning - you apparently did OK wiht your adjustment, but it is typical for the cores in old coils to stick and crack when you try to adjust them with more than a tiny amount of force. That can be a real pain if you don't have replacement cores. (Even worse, the coil form may get brittle with age and crack, and then there is no hope without an exact replacement.)

I wonder if someone here with practical experience can suggest if it's possible to lube the core with something prior to adjusting?

Glad to see you got it to work. The tools can be bought from MCM.

Bill R

Hi,

I am really happy your Philco is working well again. Everyone's posts also helped me get my identical Philco roundie combo working like new as well. Thanks everyone!

Good to hear your Philco is working too. There's more of these Philcos out there than I thought.

Well the color continued to work through the rest of the week, so I put the back back on and am done with this set for a while. Here's some more pics...

I can never seem to get the pics to come out exactly right, they're either always slightly out of focus, or have lines in them that aren't actually on the screen.

bad horizontal linearity?

The picture is "pushed together" horizontally on the left side of the screen. Actually, this set has always had this problem, but when I was working on it last, I was so happy to get it working as good as I did that I decided to watch it the way it was for a while, but now I'm getting back to it. I want to have this set working 100% before I start in on my ctc-10 (I've decided to put that RCA 6T65 that I was working on last to the side for a while, and get my 2 color sets working first). Also notice how the vertical lines are bent towards the top of the screen, I'm not sure if that's related to the horiz lin. problem or not, adjusting the fine tuning straightens the the vertical lines, but that is the best it will do. Any thoughts on where I should start looking for the source of the problems?

Does the normal TV picture show the same flagging on the top or is it just when using the generator? Often that comes from the generator.

If the 6GH8 socket continues to give trouble, tighten the pins with a dentist pick or sharp tool. If you change the socket, break it apart and unsolder one pin at a time. That will save the PC board a lot of suffering.

After I did the chroma oscillator allignment last year, I haven't had any problems at all with the color. The flagging on top happens sometimes with a normal TV picture, but not always, it is worse with the generator. Here's a pic of the same problem seen while I'm feeding the TV from a DVD player.

Have you tried adjusting the AGC to get rid of the flagging? (Use off air or DVD, not the generator.) This could be a sync separator problem that is either in the sync separator itself or simply caused by the wrong signal level going into the sync separator.

Adjusting the AGC helped some. I found that now after I adjusted the agc, it will completely go away, but only if the h hold control is adjusted just right, turn it a little bit one way or the other and the problem can be made worse making the whole screen 'wavy' not just the top, while the horiz still remains in sync. The 'wavyness' still remains with the generator.

Adjusting the hv control did away with the horiz lin problem, the control was set all the way down, I adjusted it up until the linearity was right, about 1/3 of the way. I don't have an hv probe so I can't check what the hv actually is.

I also adjusted the focus control for a better picture, before I either had to choose between too dim, or up the brightness control and get a bit blurry, I always blamed it on the crt, but now the picture is way clearer.

Yesterday the color stopped working on this set again. Eventually, I got the color back by replacing the 6GH8 chroma osc. tube (even though the tube that was in there tested good.) But with the new tube I lost color sync, so I repeated the chroma oscillator alignment procedure, and it worked. Then when I put the tube shield back on the 6GH8, it lost color sync again, and I had to do the alignment over again, this time with the tube shield on, but now the color seems to work.

While I had the set apart, I replaced the horiz. AFC two-part diode, and that completely fixed the problem this set was having with the picture bending at the top. Then I figured I would also replace that selenium rectifier on the convergence board, and touch up the convergence.

Well now the convergence is good, the color is back, the horiz problems are fixed, but when the color went out a new problem also started, with sort of 'duplicate' images to the right (see the picture below - it's off of a dvd player, not the antenna), and it's the same on both a color and a b/w picture.

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I expect it has been discussed but haven't seen it yet:
Is it not very important that the tube shields have a very good contact to the grounding tab that contacts them at the base? I had a funny color problem that got better when the shield made better contact. I was going to put deoxit on it but just polished the area and put a light CRC coat on it. I have seen some tube shields that had a ground wire soldered to them. I think that was mostly in Japan sets.

Suggest you find the luminance delay line and check all component values on either end, but especially resistors on the output side This could be a mis-termination of the delay line, causing a signal reflection.

I checked those resistors around the delay line and found none to be really bad, but I replaced a few resistors that checked around 5% off or higher anyway. The only resistor that was off by more than 10% was the 6.8k before the delay line connecting to the 150v supply which was up to 8.2k. It made some improvement, but didn't completely do away with the problem.

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The more I look at the pix off these Philcos, the more I think this is a chroma problem, not luma. A long-term ring like this has to come from some narrowband or sharp cutoff circuit. Suspects could be the IF or chroma, but I'm thinking maybe a sound trap - either misadjusted, or a poor design that bites into the upper chroma sidebands.

So - you might look at the sound trap or traps (there should be at least one) and check components and adjustment in that area.

>>Do you have a DVD with color bars? I'm thinking this might show clearly on some of the color bar edges if it's in the chroma.

Also, I recall some sets had a color take-off adjustment that was supposed to have a bandpass tilt opposite to the roll-off of the IF and sound trap. It would affect discoloration on edges, which shows in some of these pix, but I don't think it would cause that very long-term ringing. I think this adjustment was only in later Zeniths, but I thought I should mention it.

>>Can you post or link to the schematic of the last IF stage and all of the color take-off and chroma?

I think you have an issue with the sound trap. That was a weak issue on Roundie Philco sets. That and the tuner are the main difference between a Philco roundie and an RCA roundie. The Philco has very touchy adjustments and never got as good as an RCA.

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philco schematic (sams 698-4).... So far it looks the same as the ctc15 to me.

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I don't have a CTC-15 to compare it to either, but I see three sound trap adjustments:
A1, tune for minimum response at 41.24 Mhz, along with R19. A11, tune for minimum response at 4.5 MHz (intercarrier, demodulated result of 41.25 MHz).

Still couldn't tell you if the chroma ringing you see is the result of misadjustment or an unimprovable design flaw. The best thing would be a complete IF alignment first including the three sound trap adjustments, then see if it's any better.

I've never attempted the IF alignment before. And while I have 2 of those sweep signal generators - neither works. It's something I definitely want to learn to do, but as I said in another thread I'm moving to the other side of the country (with all my sets and other junk) soon, and I don't want to start anything new until I'm relocated probably a little over a month from now, so the Philco will have to sit as is for a while. I'll try and get up the sams for the ctc-15 for comparison to the Philco schematic in this thread later this week.