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Author Topic: Plate voltage booster (additional transformer)  (Read 1147 times)
N8CBX
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Posts: 131




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« on: January 25, 2013, 09:41:40 AM »

I want to experiment with adding a 240 pri/240 sec transformer in series with the plate transformer of a 500w amplifer (using 572b tubes). The current anode voltage is about 2100v, and I would expect to see about a 400v-600v increase (getting close to 3kv). Anything I need to watch out for connecting the two transformers in series?
I can easily select the secondary transformer's rating to closely match the primary one (about 1.2A)
Jan
« Last Edit: January 25, 2013, 09:47:56 AM by N8CBX » Logged

Dayton Ohio - The Birthplace of Aviation
G3RZP
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Posts: 4366




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« Reply #1 on: January 25, 2013, 09:56:13 AM »

Is it a bridge rectifier? If so, you will be better off rectifying the output of the new transformer and putting it in series with the DC of the old transformer at the negative end. This because that way, the new transformer doesn't see the volts across it (primary to secondary, secondary to frame) that it would if you just wired it straight in series with the existing xfmer secondary.
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N8CBX
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Posts: 131




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« Reply #2 on: January 25, 2013, 10:29:05 AM »

I'm sorry. The 2100v is the anode DC voltage out of the voltage doubler circuit that I am using now. The plate windings make about 800VAC @ 1.5A-1.6A, so the total AC voltage would be about 800 + 240 = 1040VAC, then connected to the doubler/rectify/filter circuit to hopefully bring it up to about 2700VDC, or close to that.
So you are saying there could be insulation breakdown in the secondary? I see that now.
Jan
« Last Edit: January 25, 2013, 10:32:29 AM by N8CBX » Logged

Dayton Ohio - The Birthplace of Aviation
G3RZP
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Posts: 4366




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« Reply #3 on: January 25, 2013, 01:03:23 PM »

Yep. By making a 240 or whatever volt DC supply and putting it in series with the rpesent HV supply but at the grounded end, you minimise the stress on the extra supply. At the cost of four more rectifiers and maybe an electrolytic and bleed resistor.
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