unidentified PT, how to establish what wire is for what...

[HTH]

hi all,

I've got a 120w PT that is the same as those used in the first Ashdown guitar amp heads that came out maybe 5 years back. Trouble is, I don't have a wiring diagram for it.

What is the method for establishing whats what ???

I've identified the wires that're on the same winding with a continuity test and also measured the resistance between the wires.

PRIMARY (I think so anyway)

* white (connected to nothing else)

* black-green: 1.5ohm (0v-120v)
* black-yellow: 4.1ohm (0v-220v?)
* black-red: 4.7ohm (0v-240v?)
* black-blue: 1.4ohm (0v-110v?)


SECONDARY (hopefully)

* green-green: 0.3ohm (heater winding, end to end?)
* green-yellow: 0.2ohm (heater CT?)

* purple-purple: 2.4ohm (winding for relays?)

* black-blue: 11.9ohm (bias?)

Does this look right?

[HTH]

its ok folks, I got this sorted.

[octal]

I'm assuming this is for a tube amp, since you referenced "heaters."
Have you already identified the HV B+ secondary, or is it possible that it's mixed up with your primary connections?

You could feed 6.3 vac INTO the two heater taps and measure your primary voltages. Use due caution!

Nathan

[octal]

Whoops. Logged out, logged back in again and you had it sorted! Well done!

[HTH]

I'm assuming this is for a tube amp, since you referenced "heaters."
Have you already identified the HV B+ secondary, or is it possible that it's mixed up with your primary connections?

You could feed 6.3 vac INTO the two heater taps and measure your primary voltages. Use due caution!

Nathan

thanks Nathan, I ended up doing exactly what you suggested - feeding 6.3vac into the heater winding. I was 90% certain of the taps before this with the resistance measurements I took, but I had to know.

a mate of mate suggested putting the 6.3vac through the primary and that does seem like a good suggestion - its way less voltage than the primaries are used to taking, so no fear of toasting anything.