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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Fri 09, 2019 2:32 am 
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Joined: Feb Wed 03, 2016 9:11 pm
Posts: 64
Location: Savannah, GA
The insulation seemed to be fairly in tact when I removed the cap. I tried looking for the filament light, and didn't see anything. I I will probably run to the store tomorrow and pick up a light bulb for one last test of the 1B3GT. At this point I am fairly certain it is bad. All other voltages in the horizontal section are looking okay. Now I wait for the new tube to arrive in the mail, but am still open to any further suggestions in the meantime. Thanks!


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Fri 09, 2019 5:02 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Phoenix, Arizona
You should be able to use an insulated screwdriver and draw an arc from the plate cap of the 1B3 just holding the handle in your hand.

I don't ground the screwdriver. It all works like a Tesla coil

Your hand holding the insulated handle.

If you get an arc the H output circuit is likely working.

If you see a dim glow from the 1B3 filament the output circuit is likely working.

Keep the good meter and fingers away from plate caps.

Jim


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Fri 09, 2019 1:01 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 314
Location: Arlington, TX, USA
If this set has any high voltage "doorknob" capacitors check to be sure they haven't gone bad and are pretty much shorting the HV supply to ground. If your set has one it will be from the output of the 1B3 to ground. I have a set here now that has several of these, one was bad right out of the gate and another failed after I had the HV supply working.


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Fri 09, 2019 3:01 pm 
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Location: Pewaukee, WI
Another thing worth checking is the frequency and waveform of the H output grid drive. If the frequency is way off and or the waveform is wrong the DC voltage could be good yet the set would have no HV.


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Sat 10, 2019 2:11 am 
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Joined: Feb Wed 03, 2016 9:11 pm
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Location: Savannah, GA
Alright, I have tried the screwdriver test. I did get a spark when holding it up next to the cap of the 1B3. My understand is that this test confirms that the H.V. is working up until the H.V. rectifier further isolating the H.V. tube as the issue?


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Sat 10, 2019 2:27 am 
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re high voltage probe
these were available for a vtvm but not for a standard multimeter. i dont know about a dmm as they didnt exist when i worked on electronics repair to the best of my knowledge.

a high voltage probe had a multiplier resistor in the probe body that was in series with the measured voltage to extend the dc voltage range of your meter as well as improved insulation. as stated above you can get one with a built in meter if you dont have a vtvm.

while a tube that doesnt have filament glow is definately bad a tube can have filament glow and still be bad. a tube tester is a usefull tool but the best test is substitution with a known good tube of the same type.

if you got the arc at the high voltage rectifier top cap then yes that means the horizontal section is producing the high voltage. your flyback transformer is working. here is where you need a high voltage probe to find out if the high voltage is low. if the high voltage measured at the 2nd anode lead is correct it would mean your crt is dead. if there was no high voltage on the 2nd anode lead it could be a dead high voltage rectifier tube or a component in the high voltage rectifier circuit.

the spark test shows the presence of high voltage but it cant tell you if that high voltage is low or not. personally i was always nervous to do the spark test because of the high voltage involved. 9kv plus on a bw crt. this is low current so it might not kill you but it will give you a good shock.


Last edited by thomas13202 on Aug Sat 10, 2019 4:05 am, edited 1 time in total.

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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Sat 10, 2019 3:25 am 
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Location: Ann Arbor, MI
thomas13202 wrote:
re high voltage probe
these were available for a vtvm but not for a standard multimeter. i dont know about a dmm as they didnt exist when i worked on electronics repair to the best of my knowledge.

They were available for the dmm also. But they had a slightly different value resistor. A VTVM typically had a 10 meg ohm input resistance and had a 1 meg ohm resistor in the probe near the probe tip. So the VTVM was calibrated expecting to see 90.0909 % of the voltage being measured at the meter itself. A dmm also has has a 10 meg ohm input resistance but has no resistor in the probe and so it is expecting 100% of the voltage under test at the meter. If you used the wrong high voltage probe, the reading would be off by about 10%. You could of course do a little arithmetic to fix that.

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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Sat 10, 2019 3:41 pm 
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Location: Dallas, TX
Chase.Parten wrote:
Alright, I have tried the screwdriver test. I did get a spark when holding it up next to the cap of the 1B3. My understand is that this test confirms that the H.V. is working up until the H.V. rectifier further isolating the H.V. tube as the issue?

The arc from the H.V. tube cap will kind of hiss and appear continually whereas the arc from the CRT is more of a snap. The tube cap is an AC voltage made of a series of pulses, the anode is DC stored in capacitance either in a "doorknob" cap or the capacitance of the CRT anode structure itself.
I'm a bit surprised that you don't have a compact fluorescent around the house, I suppose they may get rarer because of the LED versions out now. The CFL does not have to be a good one by the way, more that likely its the circuit in the base that fails. As long as the fluorescent tube is still sealed the TV test works.
Yes, you do have to read the fine print with the H.V. probes. Some of mine are for 10 Megohm meters (990 Megohm resistor) and some are for 11 Megohm meters (1090 megohm resistor). Once you know what you have however a little math will straighten things out.
I forgot that I had some probes with there own meter. One of them appeared in my previous photo which I had taken a while ago.
Attachment:
HVProbeSelfConE1.jpg
HVProbeSelfConE1.jpg [ 389.94 KiB | Viewed 564 times ]

By the way, where did you get the schematic and what type is it, SAMS, Riders, Admiral?
In most cases that I've seen, the schematic has the the warning "Do not measure." on the tube cap connection wiring.

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


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Mon 12, 2019 10:15 pm 
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Joined: Feb Wed 03, 2016 9:11 pm
Posts: 64
Location: Savannah, GA
Alright, the H.V. rectifier has been replaced, but the squealing still persist. I do get a very dim partial picture. With the test I have already done it seems to me that all voltages in the horizontal section are correct. As I said before when I first powered the set on I got a fully lit up CRT, but since then I have gotten nothing. What may be some other causes here?


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Mon 12, 2019 10:40 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 314
Location: Arlington, TX, USA
Does this set use an ion trap on the CRT neck? That partial picture looks like an out of adjustment ion trap magnet. Failing that I think you will need a HV probe to verify you have correct HV. Also make sure the horizontal oscillator is running at the correct frequency.


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 Post subject: Re: Admiral 19F1 High Voltage issue
PostPosted: Aug Mon 12, 2019 11:03 pm 
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Location: Pewaukee, WI
thomas13202 wrote:

the spark test shows the presence of high voltage but it cant tell you if that high voltage is low or not. personally i was always nervous to do the spark test because of the high voltage involved. 9kv plus on a bw crt. this is low current so it might not kill you but it will give you a good shock.


Flyback derrived HV is fairly tame. Most flybacks can just barely drive the max current a CRT can draw, and that current is usually under 1ma. 30ma is the minimum current required to kill a healthy person. I've been bit by 25KV from color TVs more than once...It is basically equivalent to the meanest household static shocks I've gotten. Though anyone with heart conditions should be warry of this level of shock as a danger to their life.

I've gotten worse bites from 120VAC, and the worst shock I can remember was from the yoke of a metal cabinet round screen color TV I had to adjust while powered . The yoke and output tube plate caps can source leathal current. I was pressed up against the cabinet at the shoulder of the arm not in the set. I took the yoke jolt the worst way possible across the chest...It triggered my reflexes HARD. The arm that touched the yoke smashed the convergence hardware and ripped the soldered blue lateral ground wire (which were in the way of it's trajectory) clean off as reflexes launched it out of the set. My thumb that touched it had a burn spot for a few days from that.

Sets that use a 60Hz line transformer to produce HV (all pre WW2 TVs and some early post war sets) and microwave ovens can supply substantially more than leathal amounts of current and should be treated with extreme caution.

B+ in most flyback based sets is more dangerous than HV since current is what kills (not voltage).

Always try to work with one hand in your pocket on a powered TV and avoid touching anything grounded as well as any part of the set with any part of your body other than your 1 working arm.


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Mon 12, 2019 11:25 pm 
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Posts: 64
Location: Savannah, GA
It was indeed the ion trap. Funny I didn't think to adjust that. I had tried adjusting it prior to replacing the H.V. rectifier, but it made no difference. I suppose that this shows that it was indeed the rectifier at fault.


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Tue 13, 2019 5:10 pm 
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Location: Savannah, GA
The set is now functioning. Needs some adjustmemts, but it seems that this is going to be a fairly easy restoration. Thank you all for the help.


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Wed 14, 2019 10:24 pm 
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Location: Savannah, GA
The set is now just about finished up. I have been letting it run for a little while now, and have noticed that there is a little bit of a hissing sound coming from the back of the CRT. This sound is accompanied by a slight burning smell. It smells almost like a cap gun. Also whenever this hissing occurs the left side starts to become distorted. I have inspected all the wires around the CRT/H.V. area and all the shielding looks intact. I did find that the base of the CRT has a crack causing the base to be a little loose. Could it be related to the crack?


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Wed 14, 2019 10:45 pm 
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Sometimes focus is tied to B+ Boost which is usually 600-1500v....if the base is twisted such that the focus lead inside the base is arcing to a lower voltage line that could explain your symptoms.

Try to confirm where the sound is coming from....A good way to do it is to take a piece of fish tank or automotive vacuum hose, stick one end in your ear and probe around with the other end listening for loudest noise.


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Thu 15, 2019 12:39 am 
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Location: Dallas, TX
Besides the focus voltage on the CRT base (if your CRT uses electrostatic focus) or the H.V. wiring the distortion on one side suggests an arc in the yoke. The yoke winding can have fairly high voltage spikes on it. The cap gun smell may be ozone which is created in an electrical discharge. The idea about using a plastic or rubber hose to localize the sound is a good one. You could also look at the chassis and CRT in the dark and perhaps see the discharge.

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


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Fri 16, 2019 1:53 am 
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It seems that I was able to get that fixed by rotating the CRT base a little ways. Still I am slaving away to get this set adjusted for optimal performance. It still doesn't seem quite there yet. What are some tricks you guys have for adjusting as far as test patterns, pattern generators, etc? I do plan to continue doing this for many years to come so the purchase of a piece of equipment to assist in getting sets adjusted is something I am willing to do. I am just not sure what to look for.


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Fri 16, 2019 2:47 am 
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The BK Precision 1077B “Television Analyst” can generate test patterns and do a bunch of other jobs that are useful in TV restoration. This article provides details, including a list of the 1077B’s many functions:

https://antiqueradio.org/BK1077BTelevisionAnalyst.htm

There are other pattern generators, of course, but many of them perform only that single function.

In this photo, my 1077B sits to the left of a Dumont TV chassis, which is displaying a pattern on an 8XP4 test CRT:

Image

Regards,

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


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Fri 16, 2019 3:27 am 
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Location: Dallas, TX
You should definitely fasten the CRT base on securely. There are rather thin wires that come through the glass of the CRT and are soldered to the hollow tube base pins. If those wires break off at the glass you will have a big problem. The best thing to do is unsolder the pins, suck out the solder, clean the base and rear of the CRT neck well and use a glue, like silicon sealant. However that is a lot so you probably can get by by cleaning the joint area as best you can, finish with alcohol. After that is completely dry, try to squeeze silicon sealant into the joint. The silicon sealant should be the "oxygen sensor safe" type, some other types can cause corrosion.
Here is another picture from Phil's site showing a "NTSC pattern generator". It is set to output a "cross hatch" pattern, it can output others. It generates the pattern electronically. There are simpler generators.
https://www.antiqueradio.org/art/DuMont ... shatch.jpg
The test pattern Phil just posted is similar to the old "Indian Head" test pattern that stations used to broadcast at night. You can Google that. That comes from a large slide that the 1077 scans.

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


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 Post subject: Re: Getting started on Admiral 19F1
PostPosted: Aug Fri 16, 2019 2:13 pm 
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Location: Arlington, TX, USA
A cheap way to get test patterns if you are handy with computers is to make a DVD with test patterns and then use a DVD player connected to the TV as a generator. I'm not sure how "calibrated" this is, but for things like crosshatch and linearity patterns it will work well. Even using a color bar pattern still resulted in decent color adjustment with normal video afterward. I have a couple of cheap players from Goodwill around here for this purpose. It's a cheap and workable alternative to getting a test pattern generator off Ebay and getting it to work. I still want to get an actual color bar generator sometime, however. There used to be a website that had a free download file that you could burn to a DVD, but it seems to be gone. I still have that file on my computer but didn't have success making another test DVD using it, so I decided to roll my own.


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