RE: Mikey Helps The Technically Challenged - Me. - Eli Duttman

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RE: Mikey Helps The Technically Challenged - Me.

Posted by Eli Duttman (A) on October 15, 2014 at 12:40:20

In Reply to: RE: Mikey Helps The Technically Challenged - Me. posted by 6bq5 on October 14, 2014 at 15:23:01:

While it is work, recovery from a failed power transformer in Scott 299Cs, 299Ds, LK72As, and LK72Bs need not be hideously expensive. The "beefed up" replacement power trafo Triode Electronics sells for Dyna ST70s can be adapted to the need.

Use 1 of the 2X 6.3 VAC windings to energize the 6 power section tubes. Voltage double, with Schottky diodes, the other 6.3 VAC winding and 7812 regulate the resulting DC, providing for the 4X 12AX7 heaters. Half wave rectify the bias tap (a Schottky diode is preferred) and CRC filter the resulting "raw" DC to obtain the C- supply.

The scheme outlined above is made possible by the fact that the heater current draw of a 7591 is less than that of an EL34. :>D

Eli D.

Upgraded ST70 Power Transformer (Open in New Window)

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Follow Ups Full Thread

Topic - Mikey Helps The Technically Challenged - Me. - geezerrocket 11:03:37 10/14/14 (12)

when the magic smoke escapes... - mhardy6647 17:34:16 10/14/14 (2)

Camera? - geezerrocket 18:31:08 10/14/14 (1)

ahh, phone - mhardy6647 04:11:20 10/15/14 (0)

Ooooo - like a laser show it is! - airtime 16:04:54 10/14/14 (0)

It must exhaust his patience to deal with some of us neophytes - Michael Samra 15:30:46 10/14/14 (0)

RE: Mikey Helps The Technically Challenged - Me. - 6bq5 12:23:27 10/14/14 (6)

RE: Mikey Helps The Technically Challenged - Me. - geezerrocket 13:32:09 10/14/14 (5)

RE: Mikey Helps The Technically Challenged - Me. - 6bq5 15:23:01 10/14/14 (4)

RE: Mikey Helps The Technically Challenged - Me. - Eli Duttman 12:40:20 10/15/14 (3)

RE: Mikey Helps The Technically Challenged - Me. - Crazy Dave 15:25:15 10/15/14 (2)

RE: Mikey Helps The Technically Challenged - Me. - Eli Duttman 12:10:21 10/16/14 (1)

Thanks! (nt). - Crazy Dave 12:28:07 10/17/14 (0)

Follow Ups

RE: Mikey Helps The Technically Challenged - Me. - Eli Duttman 12:40:20 10/15/14 (3)

RE: Mikey Helps The Technically Challenged - Me. - Crazy Dave 15:25:15 10/15/14 (2)

RE: Mikey Helps The Technically Challenged - Me. - Eli Duttman 12:10:21 10/16/14 (1)

Thanks! (nt). - Crazy Dave 12:28:07 10/17/14 (0)

RE: Mikey Helps The Technically Challenged - Me.

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