[ARC5] Transformers in low-voltage to B+ supplies

[Leslie Smith]

Re-posting a message that appears to be 'lost'.
Original mentioned a sketch - not attached in this case.

Hello Tim (and others):

Thanks for your reply (and particularly your circuit Tim).  Speaking
generally the circuit you sent is similar to others seen on VMARS (hope I
got that right).  Except:  Your cct runs at 25kHz, not a iron-core power
transformer frequency.

So - for the moment - I changed my plan.  (My  purpose in posting on ARC-5
forum was to seek info.  The system is working.)
I will move the switching frequency to 25 or 50kHz.  Up from ~100Hz (or
iron-core power transformer frequency).  Still thinking xtal control for
the switching frequency.

I intend to use a driver circuit that does not switch polarity of the
winding instantly.  The circuit here inserts one "off" clock pulse interval
between the reversal of polarity in the transformer.  With a small RC I can
soften the sharpness of the signal when each clock pulse switches off.  My
be un-necessary; time (and a CRO) will tell.

Yesterday:  I went to the local electronics shop and bought x3 pot cores to
wind the transformer.  Don't have the specs for this particular ferrite so
I will engage in some experimentation.  I hope to tap the secondary to give
60-90-120V to run the BC-454.  I will begin with the same number of turns
on the* primary *winding shown in your circuit.  The secondary will have
fewer turns.

Reading earlier postings about optimum B+ voltages I understand I'm running
well below the recommended 180 .. 250V but from experience I can say a
command set from the BC-45x series will work well on a 60V B+ supply.

I attached a sketch to the previous e-mail.  It appears to have disappeared
into that place where lost things are never seen again. Sketch is absent
this time.  Let's see if I make it this time ...

Leslie

PS:  Here's an interesting observation.  A moment ago I clicked 'send'.
Mr. Google reminded me that I wrote "I attached a sketch ... " in the body
of my text but no attachement was found.  You know why.  That suggests some
'automaton' is reading my mail.  It appears nothing is private.  Not even
an innocent message about hobby electronics.
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