Bandmaster OT for use with 6V6?

[jezzbo]

hi all,

Maybe a stupid question but.
Is it possible to use a Bandmaster OT (2X6L6 to 4Ohm) with 2X6V6 or 4X 6V6?

I friend of me gave me one for free. I would like to build a lower power amp with it.

thanks!

Jesse

[ToneMerc]

Jesse, it would work well for a 4 6V6 build.

TM

[martin manning]

Or, if lower power is what you're after, 2x 6V6 into 8 Ohms...

[jezzbo]

Thank you for your replies.

I thought so, just wasn't sure.

2X 6V6 -> 8Ohm I like.

[tubeswell]

Thank you for your replies.

I thought so, just wasn't sure.

2X 6V6 -> 8Ohm I like.

so plug in a speaker rated at 2 x the impedance of what the secondary is otherwise rated for in this instance. (i.e.: if its set up to give 4k with an 8R speaker, then plug a 16R speaker into it to get 8k).

[rdjones]

Is it possible to use a Bandmaster OT (2X6L6 to 4Ohm) with 2X6V6 or 4X 6V6?

Does the transformer have identifying marks, such as 022848 or 125A6A ?
Just curious to confirm it's what's being discussed.

If so, it's 4k primary to 4 Ohms secondary.
As has been said, this can be used for 4x6V6 into 4 Ohms, or 2x6V6 into 8.

rd

[jezzbo]

Is it possible to use a Bandmaster OT (2X6L6 to 4Ohm) with 2X6V6 or 4X 6V6?

Does the transformer have identifying marks, such as 022848 or 125A6A ?
Just curious to confirm it's what's being discussed.

If so, it's 4k primary to 4 Ohms secondary.
As has been said, this can be used for 4x6V6 into 4 Ohms, or 2x6V6 into 8.

rd

I'll poste the codes as soon that I get home this evening.

Thanks!

Jesse

[jezzbo]

Ok the codes on the OT are:

1155-1015
6050225

The colour of the wires:
primary: blue brown red
secondary: (bigger wire) yellow, black, green.

There is no brand on it.

Thanks

[dynaman]

I don't know squat about the codes, but three secondary wires would indicate a couple of different speaker loads, no?

[tubeswell]

Hook up the secondary to a small VAC source (like 5-10VAC or so), and measure the (high) VAC across the primary. (Its more accurate if you use two meters to do this so you can look at the two readings at the same time). This will give you a Pri:Sec voltage ratio. The impedance ratio is the square of the voltage ratio.

E.g. if you hooked up the secondary to the 5VAC winding of your PT (with nothing else hooked up to that 5VAC winding), and then you measure (say) 5.4VAC on your OT secondary and 108.3VAC across the OT primary, that is a voltage ratio of ~20:1 Pri:Sec, and the impedance ratio would therefore be 400:1. So if you hooked up an 8R speaker to the secondary, you would get a 3k2 load resistance. (8R x 400 = 3200R) There you go. Some homework.

Be careful doing the measurements and VAC hook-ups. You don't want any of the PT's (or OT's) windings to cross and/or short to each other or the ground (or anything). Keep them isolated (cover loose winding ends in shrink-wrap, and use insulated screw terminals for the connections) for this exercise

[Cliff Schecht]

I always use a low current function generator for testing like this. Voltages stay low and you don't have to worry about hurting anything.

[jezzbo]

wow guys, thanks for the info.
I'll try that little experiment with the 5VAC on secudary

[rdjones]

Ok the codes on the OT are:

1155-1015
6050225

The colour of the wires:
primary: blue brown red
secondary: (bigger wire) yellow, black, green.

There is no brand on it.

Thanks

Those codes are not familiar to me, but "605" will identify the manufacturer.
It may not be an original Bandmaster transformer, since I'm not aware of any Bandmasters having multitapped output.
A bit more about the transformer might be in order here.
What model year is it supposed to be from, or at least what era (eg Tweed, Brown, Blackface, Silverface) ?
What is the spacing between the mounting tabs ? 2 or 4 tabs ?
How much does it weigh ?
(inquiring minds)

Follow Tubeswell's method of determining the turns ratio, keeping in mind that the overall turns ratio of the transformer is that of the primary to the highest impedance secondary.
Tape off the tap for now and pay attention to the higher resistance secondary leads for the most accurate reading of ratio.
The tap will most likely be half the impedance of the full secondary.

rd

[ToneMerc]

Ok the codes on the OT are:

1155-1015
6050225

The colour of the wires:
primary: blue brown red
secondary: (bigger wire) yellow, black, green.

There is no brand on it.

Thanks

Here's the "605" manufacturer.

http://www.lenco-elect.com/custom_transformers.htm

TM

[jezzbo]

no, it ain't an original Bandmaster OT. Sorry I wasn't clear about that.