[R-390] More Info about the 3TF7 replacement using a high efficiency switching regulator

[David Wise]

I wondered how you found room for the reservoir cap.  Answer: With great difficulty.  :)

I took a different approach with my 3DW7.  It regulates AC RMS, not DC.  It switches at mains frequency, and lets the heaters do the filtering.
It powers itself through the load, so it does not need an earth connection.  It has a small reservoir cap, just enough to keep the microcontroller alive when the pass transistors are on.

Regards,
David Wise

-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of sigmapert
Sent: Monday, April 11, 2016 3:11 PM
To: R390A
Subject: [R-390] More Info about the 3TF7 replacement using a high efficiancy switching regulator

Hi,

as Tisha Hayes already stated there is no magic with this device. Here two links to:

a) the location of the 3TF7 and the 3TF/ replacement within the circuitry in the R-390A:

http://schmid-mainz.de/3TF7/01.jpg

b) top and bottom view of the small printed circuit board (not yet wired to the 9 pin miniature
base) as contained in the housing of the device:

http://schmid-mainz.de/3TF7/02.jpg

73 sigmapert, DH3PJ