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  #1  
Old 03-06-2017, 10:49 AM
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bigaudioal bigaudioal is offline
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I hate the RCA 630 chassis

I am working on an 8TS30 for a friend. The set was recapped by Kamakiri and was working but the contrast was terrible. I picked up the set a few months back while in Buffalo visiting. Owner of the set is close to me in VA. Kamakiri suggested replacing the four 270 pf mica coupling caps in the video IF, as these can sometimes be a problem and cause this issue. So I did. Took all of 15 minutes to replace those four caps. The originals all tested a bit high, but no higher than 320 pf. I also found a resistor that had broke free of the contrast (AGC) pot. It was going to the audio amp tube. Fired it up and I do get audio but ZERO sign of a picture. Nothing even close. Mostly just a gray raster. AGC alters that a bit, and alters audio too. All the other controls seem to work as they should. Set is putting out 9 kV to the CRT and running solid otherwise.

Could replacing these 4 micas in the video IF throw the set that much out of alignment that I would not get even a hint of a picture?

I do not have the equipment and have never done an alignment of a set. So if it is the alignment I am kinda out of luck.

I did all the easy troubleshooting items, checked/swapped tubes. Cleaned tuner, etc.

Any other suggestions?

This is the second RCA 630 chassis I have had my hands on and both have given me fits!
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Old 03-06-2017, 11:48 AM
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Electronic M Electronic M is offline
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Double check you wired in the caps correctly, and that they are the correct value.

Try disconnecting that resistor and see if it goes back to some semblance of previous operation.

Do you have a B&K 1075/76/77 analyst?...If so try using it's IF output to inject into the IF system. You could also inject video past the detector to check if a video stage failed.
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Old 03-06-2017, 12:05 PM
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Quote:
Originally Posted by Electronic M View Post
Double check you wired in the caps correctly, and that they are the correct value.

Try disconnecting that resistor and see if it goes back to some semblance of previous operation.

Do you have a B&K 1075/76/77 analyst?...If so try using it's IF output to inject into the IF system. You could also inject video past the detector to check if a video stage failed.
I double checked that the caps were all 270pf (like originals) and that they were wired in the correct spots. I also ran the set with that resistor connected and disconnected to the contrast (AGC) pot. Without it connected, no audio and contrast pot has zero affect on raster. With it connected, audio returns and raster is affected by adjusting the control. Just no picture. I do not have an analyst. Only thing I have for injecting a direct signal would be a VCR. Guess I could pass that video signal through a cap into the grids of each video stage, right?
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Old 03-06-2017, 12:49 PM
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The VCR method should work. If the cap is rated high enough voltage, and placed in series with the injection probe you should be able to do both grids and plates. It will probably not be enough amplitude to drive the final video output.

You will at least know if it is the IF if video injection works.

The analyst may have allowed you to isolate the issue down to a single stage or component...If you plan to have more than 10 TVs cross your bench I highly recommend getting a cheap B&K analyst. They do almost everything....I dare say I could get by %99 of TV repairs with just a DMM with an HV probe and an Analyst...They are that useful (if you understand signal injection/substitution based troubleshooting).
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Old 03-06-2017, 07:22 PM
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M3-SRT8 M3-SRT8 is offline
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Some of those 270pF micas are rated at 1000 volts, IIRC.

Make sure you didn't solder in a 500 volt replacement. You might of fried one.

I love 630TS/8TS30 chassis. Never let me down.

Last edited by M3-SRT8; 03-07-2017 at 05:55 AM.
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Old 03-06-2017, 07:42 PM
Crist Rigott Crist Rigott is offline
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M3-STR8 beat ne to it. Those micas should be 1000 volt rated caps.
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Old 03-06-2017, 08:53 PM
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Kevin Kuehn Kevin Kuehn is offline
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Not sure where you guys are getting the 1000 volt rating for video IF coupling caps. There's no potential for those to short and the value is not that critical.
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Old 03-06-2017, 10:28 PM
EdKozk2 EdKozk2 is offline
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My Sam's folder 54 shows 500 volt 270 pf caps for I.F. coupling.
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Old 03-06-2017, 10:39 PM
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Quote:
Originally Posted by EdKozk2 View Post
My Sam's folder 54 shows 500 volt 270 pf caps for I.F. coupling.
500 volt ought to be plenty. Since the picture completely disappeared when something was changed around the contrast control, I think I'd be looking at the DC bias on the grids of those IF tubes. The contrast control should change the voltage on those grids. If you have the Sams compare your voltages to what they list.
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Old 03-07-2017, 07:07 AM
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Both the SAMS and original service material call for 500 volt micas for the 4 coupling caps in the video IF stages.
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Old 03-07-2017, 12:21 PM
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I just scored a B&K 1075 Analyst. Thanks Kamakiri!!!! Just need to recap it when it arrives. Then I can start properly injecting signals to diagnose these types of issues. Now to figure out how to use it. Have to find the manual.

Quote:
Originally Posted by Electronic M View Post
Double check you wired in the caps correctly, and that they are the correct value.

Try disconnecting that resistor and see if it goes back to some semblance of previous operation.

Do you have a B&K 1075/76/77 analyst?...If so try using it's IF output to inject into the IF system. You could also inject video past the detector to check if a video stage failed.
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  #12  
Old 03-07-2017, 12:50 PM
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bandersen bandersen is offline
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Hmm. I think you'd find the 1077 easier to use and has a lot more features. The 1075 is pretty ancient.
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  #13  
Old 03-07-2017, 12:54 PM
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I was introduced to the 1077B, a most-helpful piece of equipment in high school vo-tech. This along with about eight 21" color TV's (RCA, Philco, GE) donated years before. Of course, the Zenith roundies were easily fixed and then sent on to the truly needy.

The older students got bored with them, yet but sets continued to be freely given to the "shop class" and I used the Analyst to locate dead tuners, IF stages, video 1-2 amps and most importantly, determine if H-oscillators were dead or flybacks shorted when HOT's red-plated.
Good times during the school day, payback for the daily crap I endured until 10th grade

I have a 1076 but have not fired it up, opting instead to use a Sencore VA-48 for the color sets Ive been doing.
I will say though, the 1075-77 series is great for older sets like that RCA ,Al.
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Old 03-07-2017, 02:08 PM
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Quote:
Originally Posted by bandersen View Post
Hmm. I think you'd find the 1077 easier to use and has a lot more features. The 1075 is pretty ancient.
The 75 ought to be sufficient for a set like this. The newer 76 and 77 were better (especially for later hybrid/SS sets) but the 75s appear to have all the bare essentials of an analyst.
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  #15  
Old 03-07-2017, 02:44 PM
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This set was a problem child from wayyyy back:

http://www.videokarma.org/showthread.php?t=265546

It did work fine when I posted last, but before Al showed up to pick it up the contrast was really weak. But, that was its ride home.....
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