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Old 06-03-2018, 09:35 AM
mbates14 mbates14 is offline
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VT-71 Ballast 17A485459 in a TS-4D?

I picked up one of these ballast tubes years ago when there were plenty on ebay. I am sure this topic has probably already been beat to death. Here and elsewhere, but.

I stuck it in my 4D but it obviously didnt work after some research as they made 2 different tubes and I was unaware at the time.

So, Is there a modification that can be done to allow the 17A485459 Ballast to work on the TS-4D? Just curious.

Last edited by mbates14; 06-03-2018 at 09:55 AM.
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Old 06-03-2018, 09:52 AM
mbates14 mbates14 is offline
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Doing some more searching, I found this:

http://antiqueradios.com/forums/view...80269#p2680269

Basically states that they removed resistor E, and moved the common tie point from pin 5 to pin 6.

So technically I could swap the wires from 5, and 6, but then I lose the 22 Ohm resistor.

But according to the TS-4D schematic, that resistor is in parallel with the audio preamp tube filament.

Question is, Why? and what would happen if it was "missing"?
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Old 06-03-2018, 10:25 AM
dieseljeep dieseljeep is offline
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Quote:
Originally Posted by mbates14 View Post
Doing some more searching, I found this:

http://antiqueradios.com/forums/view...80269#p2680269

Basically states that they removed resistor E, and moved the common tie point from pin 5 to pin 6.

So technically I could swap the wires from 5, and 6, but then I lose the 22 Ohm resistor.

But according to the TS-4D schematic, that resistor is in parallel with the audio preamp tube filament.

Question is, Why? and what would happen if it was "missing"?
The 1st audio tube is at the end of the heater string in the 600ma leg.
The 6SQ7 is a 300ma tube so the resistor has to be in parallel with the heater to equal 600ma. 22 ohm and at least 2 watt.
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Old 06-03-2018, 06:34 PM
mbates14 mbates14 is offline
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Thanks for the explanation, clears that up!
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Old 06-29-2018, 08:08 PM
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edison64 edison64 is offline
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Just a question about the ballast does anyone have a list of the ballasts used on the specific chassis I swear I had one somewhere but I just can't find it now would be handy to have
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Old 06-29-2018, 11:52 PM
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bandersen bandersen is offline
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only the ts-4j late uses the 17A485459. All the others use the 17A470303
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