Info please

[jono]

Hello I have all the parts for my st35 and will start putting it all together,i notice that all the photos i have seen all the transformers are in the same position,why in my case the 370hx cannot it also be facing the same way as the other two(1650f) is it all a matter of taste? or have i missed something thanks jono

[EWBrown]

The windings (and cores) of the power transormer should be oriented at 90 degrees from those of the two output transformers, in order to reduce any 50 Hz or 60Hz magnetic field coupling from the power transformer, which could cause an "incurable" AC hum situation.


If you use a PSU choke (like the C354), its core should also be mutually perpendicular to the OPTs and the power transformer. Fortunately, this is easy, as the choke's core (C354 and similar open frame thype chokes) is vertically oriented, which makes its orientation "orthogonally correct".

/ed B

[jono]

Ar so thats why they all the same :) Thank you

[EWBrown]

What you really want to avoid is using "open frame" power and output transformers together, I did some experimenting with this kind of trannies, and they had serious magnetic coupling problems as far as two feet / 60 cm away :o

And trying the mutually perpendiculat orientation was not of much effect, either.

I was working on a "cheap amp" 5EM7 based SET project, and was thinking of combining Hammond 125ESE and one of the 261M6 series (219 VAC @ 269 mA and 6.3VAC @ 4A) of open frame power trannies, and it would have not been a good combination. Yellow_Light_Colorz_PDT_02 :o Yellow_Light_Colorz_PDT_11

I finally assigned the 261M6 power trannie to a test power supply, whiich delvers around 250 mA @ 240 to 250VDC., and 6.3VAC @ 4 amps.

It can run a 240V, 40 watt Philips light bulb all day long without getting too warm.

/ed B