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 Post subject: Restoring a Superior TV12
PostPosted: Apr Tue 07, 2020 3:29 pm 
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Joined: Apr Tue 07, 2020 2:47 pm
Posts: 17
Location: Tucson Az
Good morning! First time back to the forum after surgery for of all things "hearing issues"! Restoring a decent TV12 tube tester. Just some case damage and a few loose sockets (tightened for now, replace later) both already done and cleaning electronic components. Looking to, at least, check calibration if I can. I have been searching around but have not found the technique for this model. Does anyone know how to do for this model? Sure would love to hear how. Thanks in advance.


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 Post subject: Re: Restoring a Superior TV12
PostPosted: Apr Tue 07, 2020 9:28 pm 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 721
Adjust power knob to get 117 volts on the secondary of the power transformer between the black lead and the blue lead with the black tracer. Adjust the value of the 300K resistor until the meter reads in the center (line adj). There are many on here that will tell you to use the 6.3 volt setting to do your calibration, that is not correct. Use the 117 volt winding, that is the way the factory did it.
Before doing the calibration check and replace all the out of spec resistors and the capacitor. You usually don't have to calibrate it after the resistors are up to spec.

DM


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 Post subject: Re: Restoring a Superior TV12
PostPosted: Apr Wed 08, 2020 5:16 am 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 4022
Location: Florida
devilsmist wrote:
....... Use the 117 volt winding, that is the way the factory did it. ....
DM


Just out of curiosity, have you seen a factory procedure? Is there one online somewhere?

RRM


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 Post subject: Re: Restoring a Superior TV12
PostPosted: Apr Wed 08, 2020 5:57 am 
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Joined: Jun Sat 15, 2019 7:43 pm
Posts: 721
Just look at the schematic, you are using the 117 volt tap to feed the meter through the resistor. Many testers will use a pot instead of the resistor, and most of them use a high voltage tap. Once that is set the other taps will fall into place.

DM


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 Post subject: Re: Restoring a Superior TV12
PostPosted: Apr Wed 08, 2020 6:11 am 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 4022
Location: Florida
The only emission tester I'm familiar with that even has a cal procedure is the Knight 600. It uses the 6.3 filament voltage with a 6V6 inserted, as the reference point . All the others just depend on the components being the correct value. That's going to work out right unless the line set rectifier is bad, then you take your best guess.

As far as I know the tube charts are made from bogey tubes so the effects of load are automatically included. Anyway, all you're looking for is for the meter to be somewhere in the top half of the scale for a good tube, not exactly precision territory.

RRM


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 Post subject: Re: Restoring a Superior TV12
PostPosted: Apr Wed 08, 2020 3:53 pm 
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Joined: Apr Tue 07, 2020 2:47 pm
Posts: 17
Location: Tucson Az
Thanks for the replies. I can try both and see what the results are. Always nice to have options. I am ahead of my progress with this query, to be sure I have a valid means to certify my confidence in this tester, but first I do need to check the resitors and caps, then on to the trial. II do have a couple other testers, so this is interesting there are no tubes or pots for adjusting like so many other testers. I do welcome any sugestions on this though the 117V looks appropriate. Thanks!


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