Power Transformer Secondary HT question

[LooseChange]

Just curious about this....
Using a PT with 300-0-300 HT leads and a 60v bias tap.  What would I get if I connect 60-0-300 to the rectifier (Say: Solid State)? Will I create a problem? Or just lower voltage and what would it be?
Thanks!

[stingray_65]

I have been curious about this too.

It's my guess that it would work, but the lack of windings on the bias tap would seriously degrade the available current.

Ray

[LooseChange]

Anyone else have a thought on this?

[sluckey]

I don't think it's a very good idea. I can't think of a single application that would benefit from doing this. It wont hurt anything, but take a look at what happens. First off, be sure to grab the 300v winding that's opposite the winding with the 60v. At the output of the rectifiers with no filter caps, you will have one big half-wave and then one little half-wave, etc., etc. You will have to use considerably bigger filter caps to smooth this waveform to usable DC. And the DC will be a lower value that if you had used 300-0-300. The value of the DC would be dependant on the size of the caps and the load current.

What did you have in mind?

[kagliostro]

If the bias is coming from a main winding tap you can use it as an intermediate tap to have less HV

see the attached schematic

if you measure your voltage from red (in the low side) to blu/red windings you will have [360v (from red to CT) + 45v (from CT to blu/red)] = 405v

if you measure from red/wht (in the low side) and blu/red you will have 375v

if you measure from the dotted red (on the top of schematic) till blu/red you will have 315v

and so on

Kagliostro

p.s.: I posted the same time as sluckey - may be there is the advantage to have less B+ but there are also other disadvantages - may be you can use the 60v tap as 0 tap (don't connect CT) and the other tap to have a 0 - 375v but if  you connect CT I agree with sluckey

[LooseChange]

Yeah, I get the hum with a lopsided AC power source. And getting the correct winding is an issue too.
The idea was to use a Tube rectifier (Sorry about the SS reference) and the CT.
My idea was to drop the B+ for a mussy brown sound.... Just a thought since I have the unused winding available.

I have used those Weber transformers with the two sets of HT windings.
Thanks!

[sluckey]

Just disconnect one of the HT leads from the recto socket. You'll now be operating a simple halfwave recto and the B+ will drop considerably. Might need bigger caps if the hum increase is too objectional.

I replaced the PT on an old '57 Harvard a few years back. The HT winding was putting out something like 300-0-200 (don't recall the exact numbers). B+ was low but still sufficient for that old amp. The owner had never noticed anything wrong with the sound. The amp was louder and had more punch with a new PT.