3.15AC-0V-3.15AC

[piperbob]

Question, I just got my Marstran power/output transformers for my Express build and haven't been able to contact Brian Wallace the past day or so. So I thought I'd ask a question here. According to the wiring diagram on the Marstran site for "Marstran TW Power Transformer" the diagram for the secondary side has taps for 3.15 V, 0 V & 3.15V. I'm familiar with the 6.3v-CT-6.3V setup for all the other amps I've built but I am not sure what to do with this 3.15V-0-3.15V type of arrangement. Any ideas?

[piperbob]

Maybe I'll answer my own question. The Marstran transformer has a tap for 3.15 & 3.15 which = 6.3 VAC accross the two wires. All the transformer diagrams I have seen show a 6.3 tap with an arrow to the other 6.3 tap, therefore 6.3 VAC. The 3.15 tap with no arrow to the other 3.15 tap faked me out I guess! To top it off I've been a designer/draftsman for 30 years and look at stuff like this every day

[passfan]

You've done well Piperbob. Normally you can just ground the centertap and I believe that is what they actually show in the layout.

[piperbob]

Do I get a prize?

[paulster]

The only difference is the specification terminology.

Brian correctly specifies his transformers as 3.15-0-3.15V, which is correct.

Others may be specified 6.3V centre-tapped, which would also be correct, as this implies 6.3V across the secondary with a centre-tap in the middle, so also 3.15-0-3.15V.

Specifying 6.3-0-6.3V would actually be incorrect as this would imply a 12.6V secondary, which isn't likely.

[passfan]

The only difference is the specification terminology.

Brian correctly specifies his transformers as 3.15-0-3.15V, which is correct.

Others may be specified 6.3V centre-tapped, which would also be correct, as this implies 6.3V across the secondary with a centre-tap in the middle, so also 3.15-0-3.15V.

Specifying 6.3-0-6.3V would actually be incorrect as this would imply a 12.6V secondary, which isn't likely.

I actually have a PT out of an old Conn organ chassis with this exact winding in it. I inadvertantly (more like a dumbass) lit up all my Rocket bottles for a couple minutes, before I realized it, across the whole winding. My 34's won't go to half volume now without crackling.

[passfan]

Do I get a prize?

You've won respect and admiration!!!

[passfan]

Maybe I'll answer my own question. The Marstran transformer has a tap for 3.15 & 3.15 which = 6.3 VAC accross the two wires. All the transformer diagrams I have seen show a 6.3 tap with an arrow to the other 6.3 tap, therefore 6.3 VAC. The 3.15 tap with no arrow to the other 3.15 tap faked me out I guess! To top it off I've been a designer/draftsman for 30 years and look at stuff like this every day

I once watched a job superintendant and foreman from a large electrical contractor with over 50 years of experience between them try to figure out how to hook up a single phase secondary winding on a transformer. They didn't know where to hook up the neutral and were afraid that XO would short out the whole secondary. Didn't understand anything about the winding resistance representing a load and not a short, or any of the like. They actually called the manufacturer to ask???? Of course, the only dumd question is the one you don't ask, right?

[piperbob]

passfan wrote:

the only dumb question is the one you don't ask, right?

True. Now and then I have to supervise people at work to help me get a job done. I have much more respect for someone that asks a lot of questions rather than someone assuming a bunch of things and coming up to me and saying "I'm done now what? and giving me something I didn't ask for and can't recognize. I get asked questions all the time that I can't answer. I don't mind saying "I don't know". Watch out for the know it all types. The road to hell is paved with good intentions.