Techtalk

Hey Volker,

Why do we need 2x6.3 supplies? Can't I just run all the heaters together?

-Chuck

of course you can run the heaters all together (6.3V 4A)

The transformer I picked out is

250-0-250 / 6.3 @ 3A / 12.6 @ 2A

Hopefully the 6.3 @ 3A will be enough to heat up all the tubes?

The 12.6 will be the source for the 5VDC circuit. The LM7805 input range is 5-18V for a fixed 5VDC output, so it should work fine.

Found it here :
http://www.toroid-transformer.com/
For $23.00 USD which is very cheap.

I already bought from this guy and he is really great to deal with. The quality is very high.

-Chuck

ChuckD hat geschrieben:Hopefully the 6.3 @ 3A will be enough to heat up all the tubes?

12AX7A Ih = 0.3, 12BH7A Ih = 0.6, 6AQ5-A Ih = 0.45
all together this is 3.3A

Damn I better keep looking thanks for the specs on those tubes Volker I should have looked that up myself.

-Chuck

very handy:
http://www.duncanamps.com/tdslpe/index.html

I am doing a little research into the power supply:
Trying to figure out the max-min VAC transfomer I can use.

Here are 2 schematics of it :






I can't read the voltages on the second schematic but I am thinking that the numbers don't match the Full Wave CT Rectifier Calculation:

VAC = 1.7 x ( VDC + 1 )
IAC = 1.2 x IDC
WATTS = VDC x IDC ( output )


That would give 500VAC --> 293 VDC roughly.
Then Across a Voltage divider of 4.7K to 470k
Gives 290VDC

But the schematics read 275 VDC ?

Someone want to explain? And if this is true I could get away with a 460VCT or 550VCT ?

-Chuck

load (just what I think)
this is unregulated, the whole circuit does matter, not only the PSU.
and just because of this, the tolerance they had with components AND voltage: my bet is you will be fine with either, 460VCT or 550VCT.

(I even don't know the internal voltages mine has, didn't thought of it, didn't measured it - since it just worked)

now i finally got the original Rondo 60VA V. Mayer

but it works primär also for 115v. unfortnely this is the first transformer with this feature on my desk.

it has two pair of yellow-white Litze primär. How should i connectthem for 240v

Intuitivly i would put one pair yellow-white to L and one pair yellow-white to N.

Or should i connect one Litze together, and the other two to L and N?


Lars.

Hi Lars,

think of it as a transformer with a center tap, for this beast at the primary side. Measure first, to assure yourself wich wires belong to each winding. Then connect one wire of the transformers primary side to the next of the other primary winding. This junction would be your (for no further use, don't connect anything other to this point) center tap, connecting your primaries in series, giving the required 230V terminals at the remaining 2 outer wires.
In case its white/yellow for each primary, it would look like


Paralleling the two windings will most probably result in a blown fuse or a smoking transformer because of core saturation.

-Harpo

Harpo hat geschrieben:Paralleling the two windings will most probably result in a blown fuse or a smoking transformer because of core saturation

... but would be right for 115V

the drawing is right Harpo made is right.
but why don't you do it switchable ?
if you move to the states, or the EU decides to go 115V ...

same thing with the two 250V secondary: they have to be connected in series, but to get the 250 - 0 - 250 right they have to be in phase.
since Frau Müller doesn't mark the beginning and end of secondary windings you have to measure it

Like this

yes, thats the way I do it in all my DIY equipment

but to get the 250 - 0 - 250 right they have to be in phase

Ok Thx. But how can i measure it?

Hmm, das einloggen vergessen...