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  #1  
Old 11-26-2017, 03:49 AM
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Regal TV restoration thread

I have a Regal TV on the bench, which is almost the same as a 630 circuit except for being suped-up to sweep a 17" tube. The Rider schematic is a near 630 copy-and-paste down to the same part numbers. The Regal has a HV doubler and there are slight differences in audio and video output stages--and almost nowhere else.

Anyway, the horizontal oscillator runs way too slow and stops before the adjustments take it high enough. I can keep light on the screen with a strong, focused raster way down to a frequency that is easily audible. Going to the other extreme however, the raster begins to bloom and dim, disappearing entirely not far above 15kHz.

Even at a lower freq, the oscillator always quits suddenly after about ten minutes. The 6BG6 looks angry even when there is drive. Where do I go
from there?
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Old 11-28-2017, 07:20 PM
EdKozk2 EdKozk2 is offline
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Hi David,
Just curious, did you solve the oscillator trouble? The RA 109 Dumont I finished last week has almost the same oscillator circuit as your Regal set.
Ed
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Old 11-28-2017, 08:52 PM
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I had a color set that did this (CTC-5) & it was because I wired in a cap wrong; it was throwing the frequency way off. Took years for me to find my mistake.
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Old 11-28-2017, 09:30 PM
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Ed: haven't touched it since I posted, would be very interested in how you solved the problem.

Bryan: The symptom has barely changed at all from the time that there was nothing new but electrolytics up til the present with most of the paper caps replaced including all in the horizontal section. Which cap sets the frequency in this schematic?
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Old 11-28-2017, 11:02 PM
EdKozk2 EdKozk2 is offline
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Dave, you mentioned that you have a Regal set with the high voltage doubler circuit. Riders volume 6-3 and 6-6 show a different circuit part for the frequency determining capacitors of the hartley horizontal tank circuit. Capacitor C169 (.015mf) also has a 1200 pf capacitor connected in parallel. Make sure your 6K6 and 6AC7 tubes are ok .
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Old 11-28-2017, 11:13 PM
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I do have the Rider volume; my set is the 17HD31. I swapped out the 6K6 with no change earlier. I'll check the 6AC7 and confirm correct component values.
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Old 11-28-2017, 11:27 PM
EdKozk2 EdKozk2 is offline
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If changing or modifying C169 doesn't help, then I would start checking the voltage readings of the 6K6 and 6AC7. The voltage checks should let you know if any of the resistors are way off. Do this after your 10 minute warm up period. Remove your 6BG6 before the voltage tests, that way the 6BG6 won't red plate.
My Dumont had the wrong Sync Disc transformer which caused all kinds of issues.
Also check terminal A,B,& C of the Sync Disc for proper resistance readings as shown in the schematic.
Ed
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Old 11-28-2017, 11:47 PM
EdKozk2 EdKozk2 is offline
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You can also remove V123 the 6AL5 Sync-Dscr tube when checking the horizontal oscillator frequency. It just won't sync lock.
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  #9  
Old 11-29-2017, 12:47 AM
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FIXED! One cap was hiding under the oscillator transformer, another, heh, in plain sight. Thanks for your help. Now on to the next problem(sssss)....
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Old 12-04-2017, 08:11 PM
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As soon as the back came off this set, my first task was to become intimately familiar with the power supply so that I could get all the replacement electrolytics in place before powering up. The power supply section was an exact copy of an RCA 630TS, but I've discovered more and more differences as I proceed, so here's Rider's schematic for the Regal 17HD31.

Almost every paper cap is gone now, the only ones remaining being around the audio section which nevertheless works very well. The problem I have now is one I've never heard of happening. The first picture is of a man and woman outside in daylight; the woman, on the right, is holding a microphone.
As you can see, video is rendered in the negative and, depending on content, the horizontal sync is anywhere from stable to waving around wildly. At least if the source material is in color. I discovered quite by accident that black and white content, while very far from perfect, is entirely recognizable as seen in the second shot of two folks I'm sure you can identify. The pictures were taken with no adjustments having been made in between.

I've experimented with content that is new and sharp, old and dull, full of contrast or mostly lacking contrast and the one constant is that if it's black & white it shows up in black & white and if it's color it doesn't show up as anything recognizable. What could be causing these sort of symptoms?
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Old 12-04-2017, 10:33 PM
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Perhaps fine-tuning/alignment is set to favor the chroma sub-carrier section of the RF signal.
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Old 12-04-2017, 11:09 PM
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That's my guess too - tuning or alignment is off, putting the video carrier way down the IF curve and the chroma way up. Is it possible that you are using a simple double sideband modulator and are tuned to the lower sideband channel?
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Old 12-04-2017, 11:50 PM
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I didn't suspect an alignment issue because best picture and best sound are spot on. Of course "best" is relative with a picture like that. I'm using a Radio Shack modulator, the same one I've had for some 15 or so years that has been used with many sets, both black & white and color, old and new. It's also feeding a Muntz set that I recently brought down from upstairs where I use a different modulator. That set is still perfectly tuned. If it weren't it would be an issue b/c the fine tuning is concealed.

The way things have gone with this set anything is possible. Sounds like it's scope time.

As always, thanks for the advice.
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