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 Post subject: Admiral 19A11 schematic (now with picture)
PostPosted: May Mon 06, 2019 1:06 am 
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Location: Warren, Ohio, USA
I just purchased this TV. It will be a couple of weeks until I can pick it up so I’ve started looking over the schematic. I’ve restored over two dozen radios; this will be my first TV.

http://www.earlytelevision.org/pdf/admiral_19a1_rider_tv3.pdf

Perhaps I’m missing something really obvious but can someone tell me how the video IF and RF tubes get B+?

I’m looking forward to this restoration. It’s a new challenge!!

Thanks!


Last edited by Steve Chambers on Jun Sun 30, 2019 3:31 am, edited 3 times in total.

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 Post subject: Re: Admiral 19A11 schematic
PostPosted: May Mon 06, 2019 2:32 am 
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The audio output tube acts as a voltage regulator for the other tubes you mentioned. The required plate supply voltage of the 6AS5 is relatively low, so the cathode of the audio output is able to be a large amount over ground and all series current for the other tubes runs thru this output. A filter is used to prevent the audio from interacting with the other stages.


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 Post subject: Re: Admiral 19A11 schematic
PostPosted: May Mon 06, 2019 2:27 pm 
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Scott wrote:
The audio output tube acts as a voltage regulator for the other tubes you mentioned. The required plate supply voltage of the 6AS5 is relatively low, so the cathode of the audio output is able to be a large amount over ground and all series current for the other tubes runs thru this output. A filter is used to prevent the audio from interacting with the other stages.


Thanks, but I still don’t see the path from the power supply.


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 Post subject: Re: Admiral 19A11 schematic
PostPosted: May Mon 06, 2019 5:26 pm 
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The power supply connects to one end of the primary of the audio output transformer. Power flows through the transformer to the plate of the audio output tube. Power then flows through the audio output tube to the cathode. The cathode then feeds power to the IF, RF and video tubes.

So if your audio output tube fails, you will loose your picture. Exactly what you would expect, right? :? And a weak audio output tube can cause low B+ on the IF, RF and video tubes, causing problems with the picture.

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 Post subject: Re: Admiral 19A11 schematic
PostPosted: May Mon 06, 2019 6:22 pm 
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Tom Schulz wrote:
The power supply connects to one end of the primary of the audio output transformer. Power flows through the transformer to the plate of the audio output tube. Power then flows through the audio output tube to the cathode. The cathode then feeds power to the IF, RF and video tubes.

So if your audio output tube fails, you will loose your picture. Exactly what you would expect, right? :? And a weak audio output tube can cause low B+ on the IF, RF and video tubes, causing problems with the picture.


Wow. I wouldn’t have expected that. Thanks!


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 Post subject: Re: Admiral 19A11 schematic
PostPosted: May Wed 08, 2019 3:11 pm 
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On another note but still a good point to know, if the Transformer has a red one or a red line or dot on it, which may be faded by now to a funky pink, you have an early version the schematics differ slightly but not so much that you couldn't interchange one for the other. These sets are incredible performers and very reliable and have a surprisingly good picture 4 in Electrostat set


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Sun 09, 2019 1:00 am 
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I have started restoration on this television. It's in great shape and looks to have never been worked on before. I replaced all of the electrolytic and high voltage caps and brought up the voltage slowly. At about 80 volts I get a nice bright raster BUT every minute or two I get a nice spark coming from (I think) the horizontal centering control. During the split second of the spark the raster disappears. I don't want to go any further without some idea of what could be wrong here. This is my first TV restoration.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Sun 09, 2019 1:41 am 
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It's quite possible that the control has developed some tin whiskers inside which could be causing a momentary Short Circuit... Your best bet would be to replace the control or at least see if you can clean it or get it open. It could also be an issue with the wire wound Trace having a bad spot or a corroded spot.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Sun 09, 2019 1:51 am 
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edison64 wrote:
It's quite possible that the control has developed some tin whiskers inside which could be causing a momentary Short Circuit... Your best bet would be to replace the control or at least see if you can clean it or get it open. It could also be an issue with the wire wound Trace having a bad spot or a corroded spot.



Thanks. I’m guessing since this pot has a tap it would be difficult to find a replacement so I’ll see if I can open it up and take a look.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Tue 11, 2019 1:17 am 
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I removed the pot and gave it a good cleaning. I didn’t see any obvious problems. Reassembled and also replaced two resistors that were connected to it. I applied power and at first there was no arcing. I got a picture that was out of focus but seemed to be stable and I got sound too. Then there was a snap and the picture went dead. I suppose I have no high voltage now but I can’t seem to find anything open. I’m not sure where to go next.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Tue 11, 2019 3:29 pm 
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I would start with checking all the resistors that are connected to the H.V. voltage. Check all the high value resistors in the section connected to focus, horizontal and vertical centering. Make sure you replaced ALL the high voltage caps and they have the right value. Be aware that 6500 volts can jump a good distance especially if the conductors have sharp points, it also can travel along any dirty surface.
Second check all the power supply points.
Third, you might need to get a H.V. probe for your meter, or build a substitute. You may need to trace or adjust the H.V.

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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Fri 14, 2019 5:09 pm 
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I'm still stumped. No light on the screen. I don't have a high voltage probe so I can't be sure whether or or not I have high voltage. I think I have checked everything. Coils, resistors. There are a couple of high voltage mica caps that I'll try replacing when I receive them. The picture tube filament does light. All the tubes test good. I'm a little leery of the high voltage but I see one for about $75 on Digi-Key that I might have to order. There has to be something I'm missing.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Fri 14, 2019 5:51 pm 
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Don't know about Admiral but Motorola used a spring wrapped around the HV rect tube as part of the positive feedback loop that formed the HV oscillator... If the spring was not optimally placed it would result in low or no HV...


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Fri 14, 2019 9:58 pm 
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:oops:
Somehow the brightness control was turned all the way down. I could have sworn that the picture disappeared after an arc and wouldn't come back. I now have a picture again. I'm still trying to figure out the arc that I get every so often. The picture is not super clear but appears to be stable. I'm going to continue the recap as I have time. It wants to work anyway.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Fri 14, 2019 10:29 pm 
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If you play your TV in a completely dark room, you might be able to spot a spark when it does the periodic arc. If it makes a snapping sound, you can also hold a length of flexible tubing (maybe 1/2-inch diameter) to your ear and move the other end around near the chassis, using it like a stethoscope.

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


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Fri 14, 2019 10:46 pm 
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philsoldradios wrote:
If you play your TV in a completely dark room, you might be able to spot a spark when it does the periodic arc. If it makes a snapping sound, you can also hold a length of flexible tubing (maybe 1/2-inch diameter) to your ear and move the other end around near the chassis, using it like a stethoscope.

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


Thanks Phil. I was just running the tv and it looks like the spark is jumping from one of the replacement 6kv replacement caps to the body of the horizontal centering control. It looks like the spaghetti sleeve is just short of covering the entire lead. Of course the old caps had no sleeving at all.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Sat 15, 2019 2:36 am 
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Aside from the fact that the H.V. in a TV can jump a distance through the air there is not that much danger. The current available is very low. It can make you jump and you might hurt yourself that way however. The B+ on the other hand can be very nasty, in this TV it is about 255 volts and the current is backed up with the charge on the filter caps.
If this is the only TV that you will work on you probably don't need a H.V. probe (sometimes called a multiplier probe) for your meter. They are very simple, they just contain a special very high value resistor built to withstand the voltage. The resistor forms a divider with the meter input resistance.
If you meter input is 10 Megohm and the resistor in the probe is 990 Megohm, them the measured voltage is 100X the meter reading. After having one for many years, I won an auction on a box of stuff for $20 and among the items was four H.V. probes. One of them was a self contained unit with a small meter, not pictured here.
Attachment:
HVProbesE1.jpg
HVProbesE1.jpg [ 181.66 KiB | Viewed 1460 times ]

I think if you keep looking you may find one eventually for $20-30.

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It's not the Destination, It's the Journey.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Tue 18, 2019 8:36 pm 
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The set is completely recapped but I'm not satisfied it's getting the picture it should and the arcing problem is still there. The picture is stable and can be focused ok but the vertical is maxed out and it's still not quite tall enough. The vertical linearity control does nothing. If I turn up the brightness the top ¼ of the raster is just light, no picture. I've been very careful with the recapping and I've replaced all the out of tolerance resistors that I can find and I've tried moving the spring coupling on the 1B3 tube. No change noted. I have no way of measuring the high voltage. The arcing is very intermittent; usually the picture snaps right back. A couple of times it has not come back without turning the set off for a while.

Does anyone have any suggestions?

Thanks!


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Tue 18, 2019 9:34 pm 
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If you are getting a picture on the CRT you probably have H.V. I was thinking that you have too much and that was causing the arcing, but it isn't very likely. Did you try looking for the location in the dark?
There could be something arcing internally.
You very much could have two separate problems.
Vertical linearity? I don't see that control on the schematic. Have you replaced any tubes?

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It's not the Destination, It's the Journey.


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 Post subject: Re: Admiral 19A11 schematic (new questions)
PostPosted: Jun Tue 18, 2019 9:48 pm 
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Try to stop the arcing. If the lead is long you can shrink a small diameter heat shrink over the lead up to the solder connection then slip a larger diameter piece just longer than the solder joint onto the lead slid back against the cap body, then solder the joint slip the big diameter over the exposed joint and shrink it. You can also use silicone caulk as an insulator if need be. If you stop the arcing but the HV or focus still are unstable the first thing you should do is track down a HV probe...I just saw one with built in meter for $12 at a hamfest. They are out there cheap if you look. Some problems are only practical to solve with the right tool.

Did you use ceramic or film dielectric caps for the new replacements in the sweep/HV? Ceramic caps need to be double the capacitance of the original paper caps or vertical non-linearity or insufficient height will result. Film caps should be used in the HV and deflection if at all possible.

Do you have a test pattern generator designed for TV repair? If so try injecting video past the detector and see what the picture looks like. If it is good detector, tuner, IF and AGC (if it has AGC) are suspect. If video is bad video amps, CRT/CRT HV and bias circuits are suspect.


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