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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 05, 2019 7:31 pm 
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Thanks Tom! That is a help. It explains a lot in the vertical section. I am still a little at a loss on what I call the "mystery" section, those additional caps near the front of the set. It isn't documented anywhere I can find. I have some caps on order to finish the resto. Found a couple weak tubes in the IF section. I'm going to give a careful going through on the sync and AGC section after I finish the power supply.

The tube location chart on mine matches except for the tuner, vertical amp, and the 6C4 socket looks like it has been rewired. I bet there is documentation on this if I knew where to look.

Had to take a break for a couple weeks to do other projects.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 05, 2019 8:37 pm 
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On that 6C4 to 6BF6 change. I see two possible explanations. One is that the factory changed tube types for some reason, perhaps they had a problem getting 6C4s. The other is that some TV service man rewired the socket and changed tubes because he had a 6BF6 and didn't have a 6C4. Generally when a service man rewires something the wiring looks different from what the factory wiring looks like. If it looks like the set left the factory with a 6BF6 in it then I would think that the change is OK. If it looks like a serviceman changed it then the change is somewhat suspect.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Sat 14, 2020 2:55 am 
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Well, after some time, I finally felt like doing something in the radio room. I have the E-caps re-stuffed and am going to change the rectifiers, then test out to see where I am. Still have some lower voltage caps to change. Got to dig around and find some diodes.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Mon 16, 2020 7:17 pm 
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I got the rectifiers replaced. I just stick a bridge in there and it works. The B+ came up quite a bit, around 340v, but it I still have sync issues. Both horizontal and vertical. Pic is very weak unless I inject a video signal into the 1st amp, even with a good signal, the sync is still out of whack. Im concentrating on the sync separator/agc area. They have a 6BF6 in place of a 6C4. The socket was rewired, so I'm wondering of this could be contributing. I replaced it with a 6AQ6 with no change. I'm going after the micas and resistors in this area. Voltages are off as well.

I replaced the 5J6 with a NOS 6J6a in the tuner, which is the correct tube. I lost both sound and video. I swapped it back and I got my sound back, but the video is weaker and comes and goes. Sounding like a tuner problem. Who knows. May be the agc gone cuckoo.

Edit: I also noted that I need to turn up the horizontal drive to get the horiz to sync, otherwise there isnt enough range on the hold control. So, I get a line in the middle of the screen vertically or a foldover. If I back it down, the line goes away but no sync. It also "rolls" horizontally at times.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 17, 2020 1:50 am 
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For the sync:
The sync separator is a funny sort of amplifier. It is run with somewhat funny voltages so that it will amplify part of the signal and cut off most of the signal. The 6BF6 is sort of similar to the 6C4 but is not exactly the same. I expect that some of the resistors would have to have different values for a 6BF6 to work correctly.
So if all the resistors have the values shown in the schematic, and especially if the soldering on the tube socket looks different from the rest of the set, I think that you should rewire the tube socket and put in a 6C4.

For the tuner:
You may need to clean the tube sockets. Get a little contact cleaner into the sockets and insert and pull the tubes a few times to clean the sockets. Also the moving contacts in the tuner may have to be cleaned. If that does not help, check for resistors that are way off of the correct value. If you change any resistors, the new resistor has to be put in in exactly the same position as the old one.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 17, 2020 3:37 am 
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Thanks Tom. Ill look at that. I also found some caps that I think disguised to look like micas that are really paper. So, I'll put the 6C4 back and check the resistors. Could be enough to throw things off.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 17, 2020 3:50 am 
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Some types of flat molded paper capacitors look similar to flat mica capacitors. This article has photos and more details about identifying and replacing old caps:

https://antiqueradio.org/recap.htm

Regards,

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


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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 17, 2020 5:53 am 
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TV MAN wrote:
I also found some caps that I think disguised to look like micas that are really paper.

If the brand name is micamold it is very likely to be paper inside. Some other brands made some too.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 17, 2020 8:04 pm 
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TV MAN wrote:
I got the rectifiers replaced. I just stick a bridge in there and it works. The B+ came up quite a bit, around 340v, but it I still have sync issues. Both horizontal and vertical. Pic is very weak unless I inject a video signal into the 1st amp, even with a good signal, the sync is still out of whack. Im concentrating on the sync separator/agc area. They have a 6BF6 in place of a 6C4. The socket was rewired, so I'm wondering of this could be contributing. I replaced it with a 6AQ6 with no change. I'm going after the micas and resistors in this area. Voltages are off as well.

I replaced the 5J6 with a NOS 6J6a in the tuner, which is the correct tube. I lost both sound and video. I swapped it back and I got my sound back, but the video is weaker and comes and goes. Sounding like a tuner problem. Who knows. May be the agc gone cuckoo.

Edit: I also noted that I need to turn up the horizontal drive to get the horiz to sync, otherwise there isnt enough range on the hold control. So, I get a line in the middle of the screen vertically or a foldover. If I back it down, the line goes away but no sync. It also "rolls" horizontally at times.

Attachment:
IMG_0657.jpg


You should change the 3 reddish caps in the top right of the picture 2 are paper caps with plastic shells and the other looks to be a lytic.


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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Sun 22, 2020 11:25 pm 
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Thanks Tom and EM, I'm working on the rest of the caps. I'm replacing everything in the sync, oscillators and AGC, including the micas and resistors. I started to change the 6BF6 back to a 6C4 and this has led me back to what I call the "mystery" section, so I am stumped - again. There's more to the change than a tube swap. It is using the diode plates of the tube leading to a resistor/capacitor network at the front of the set - NOT in any schematic I can find.

EDIT: Tom, I looked at the picture of yours in your thread and mine is different. Yours doesn't have that "mystery" section, and yours looks like it has a different tuner than mine. Mine seems to be a mix between the 200 and 201 and possibly something else. Got me scratching my head lol

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The purple looking wire comes off the diode plates and goes here. I had problems figuring out what cap to replace the lower cap with. The plate resistor looks original on the 6BF6 and the other components look original too. I didn't get any change in the sync (or lack of) when I changed the mystery cap either. So - unless I can figure out what this does and why the change was made, I probably best leave things alone.
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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Mon 23, 2020 5:31 pm 
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That looks like a factory installed terminal strip, so the change could have been a factory modification. In that case, once you replace the capacitors and resistors, it might start working.
If not, or perhaps even if it does work, you might want to make a copy of the schematic and then start drawing in the extra parts. That is, make your own schematic. If you could scan or take a picture of that and post it we could figure out what was done and why.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Mon 23, 2020 7:41 pm 
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Tom, it looks like it has something to do with the tuner. It may be a form of AGC or something. Ill sketch things out and see if some sense can be made of this.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Tue 24, 2020 3:41 pm 
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I'm working on a diagram. It looks like it is indeed connected to the AGC. As soon as I have something legible, Ill post.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Mar Thu 26, 2020 5:28 pm 
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Just for comparison sake here's the RC-200 pages I photographed from Riders. Per alignment instructions I would try pulling the AGC tube and subbing the negative 3 volts (or an adjustable voltage) on the AGC line. This TV has keyed, or gated AGC.

https://www.flickr.com/photos/152661900 ... 3634054282


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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Nov Thu 26, 2020 2:23 am 
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Thanks Kevin! My work is done for the season, the weather is getting lousy so I am back on the project. I did some recapping in the sync section and replaced some off value resistors but no improvement. Im working on my B&K 1077B analyst and hopefully can make some better tests. Been reading about DC restoration on the video amp and says this can affect the sync. Ill get back a little later.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Nov Sat 28, 2020 4:30 am 
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It's good to see that you are making progress! The 6BL7 is an uprated replacement for the 6SN7, intended for vertical output stage use.

I have a much older Crosley 307TA that I will be getting back to in the new year.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Dec Fri 04, 2020 4:21 am 
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I got the audio section recapped. I was doing some tests and saw the cathode resistor boiling wax, so I stuck my meter on the G1 and saw 18v on one tube and 30v on the other. Suppose to be 0v, so it was a bit high. This completes the recapatitation of this TV, unless I need to go after some mica caps or a paper cap hiding somewhere (like the yoke). So, now to the troubleshooting. I want to get the BK1077 running so I can hopefully isolate the problem(s).
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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Dec Mon 07, 2020 12:16 am 
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Trying to do some troubleshooting but didn't accomplish much. Except blowing up the video out jack on my DVD. Live and learn. I injected a RF signal into the tuner from a modulator and have really good sound, no video. Blank screen. I can get "interference" if I flip up or down a channel, but cant fine tune it in. I can fine tune the sound in perfectly. I have tried both ch 3 and 4 with the same results. So, I pulled the AGC tube, no change. I injected a video signal into the detector tube on the IF side, nothing really. After the detector I get decent video, but not quite right. Sync very unstable. I tried injecting the signal a little before the detector (for no good reason) and killed my DVD video out (with blocking capacitor in line). This pic is from using a composite signal from my DVD that I haven't blown up yet.

Since this is a split carrier set, it is possible to get perfect, tunable sound with no video? In other words, tuner probably ok? Now, I can get video from the tuner for a few seconds when I 1st power on the set, then it fades and a little screen (very faint) of the DVD menu after.
I swapped the 6AL5 detector tube with no change. I reduced line voltage down to see if it would come in, but then lost most of my vertical sweep. It came back then went off again and popped back on after touching the supply lug to the vertical output. Probably need to resolder. Anyway, I'm hung until I get that analyzer going. Other than voltage checks and tube swaps, I am hung. I did wiggle the IF tubes to see of anything happened - it didn't. So, any thoughts?

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Dec Mon 07, 2020 6:15 am 
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On a split sound set you can get good sound and blurry video if the sound and video IF strips are not aligned correctly. No video with good sound would be something wrong in the video IF strip, the video detector or the AGC over doing it and cutting off the video IF strip. But for an AGC problem I would expect something on the screen. You can tell what the AGC is doing by measuring the AGC voltage being fed to the IF strip.
In any case the tuner has to be working to get sound.

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 Post subject: Re: The Craftsmen RC 200 resto
PostPosted: Dec Mon 07, 2020 5:48 pm 
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Thanks Tom! I thought that would be the case but I wasn't sure. That shows the tuner is likely ok. I tested the tubes in the IF, but they checked ok to a little weak. I may sub them one by one and see of I get any change. Think I have a couple NOS around. I'd scope, but the scope isn't working right. I am a little weak in that respect anyway. Need to use it more :( . It'll be my next project after I get the analyst going, either that or I will look for a good used Tektronix.

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