Replacing the Power Trafo

Posted by Eli Duttman (A) on October 8, 2006 at 03:25:25

In Reply to: BTW, posted by sser2 on October 7, 2006 at 16:30:55:

I think you have miscalculated the 6.3 VAC requirement. A pair of triode/pentode (7199/6GH8/6U8) voltage gain/phase splitters draw 0.9 A. 4X EL84 "finals" draw 3.04 A. So, the total 6.3 VAC draw is 3.94 A. A 4 A. or better heater winding is needed.

Electrically, the Hammond 373BX is "up to snuff". The rectifier winding is 350-0-350/175 mA. The 5 VAC winding is 3A. The 6.3 VAC winding is 5A. The 50 VAC bias tap is fine used ONLY for bias. A piece of sheet metal, screws, lock washers, and nuts will close the hole removing the OEM drop thru power trafo leaves. All that remains is to provide DC heater power to the 'X7s.

The switched accessory outlet can support a "wall wart". Mouser stock # 418-TR1518 is a $12.99 18 VDC/830 mA. switching unit. Pass the O/P of the WW thru a choke to kill switching noise and feed 2X 7812 3 terminal regulators. A 100 nF. film cap. goes across the I/P of each 7812. 4.7 muF. 'lytics go across the 7812 O/Ps. A 4.7 muF. 'lytic paralleled by a 100 nF. ceramic goes across pins 4 and 5 of each 12AX7 socket.

Eli D.

This post is made possible by the generous support of people like you and our sponsors:

Follow Ups Full Thread

Topic - Quality of Scott 222c output transfomers compared to Dynaco Z-565? - youropinioncounts 17:39:05 10/04/06 (17)

BTW, - sser2 16:30:55 10/07/06 (4)

Replacing the Power Trafo - Eli Duttman 03:25:25 10/08/06 (0)

Re: BTW, - Eli Duttman 18:57:06 10/07/06 (2)

errrr...Eli? - Sector-7G 18:46:13 10/09/06 (0)

That's true. - sser2 20:00:49 10/07/06 (0)

Just do it! PP Triode if you're speakers can take it - Jim Doyle 13:28:15 10/07/06 (3)

Re: Just do it! PP Triode if you're speakers can take it - Eli Duttman 16:06:48 10/07/06 (2)

Optimizations w/ Triode ST35 Power Transformer - Jim Doyle 22:59:05 10/07/06 (1)

Re: Optimizations w/ Triode ST35 Power Transformer - Eli Duttman 03:53:06 10/08/06 (0)

More of a question than answer - sser2 18:43:29 10/04/06 (7)

Actually, the Dyna stuff also did well in those tests.... - JimL 08:41:20 10/12/06 (0)

Re: More of a question than answer - Kyle K 19:02:54 10/04/06 (5)

One Test to Add - Triode_Kingdom 22:44:01 10/04/06 (3)

well... - Sector-7G 17:22:23 10/07/06 (2)

Wheat and chaff - Triode_Kingdom 21:17:43 10/07/06 (1)

maybe... - Sector-7G 07:15:05 10/08/06 (0)

Yup, that's it, thanks! nt - sser2 19:16:17 10/04/06 (0)

Follow Ups

Replacing the Power Trafo - Eli Duttman 03:25:25 10/08/06 (0)

You can not post to an archived thread.