B-15N Power transformer replacement

[Enzo]

On a transformer, the primary is the winding where the power goes in. In the case of a power transformer, this would be the winding the 120v mains connect to. (or 240v in other parts of the world.) All the other windings are secondary windings. They are the specific voltages created by the transformer for use in the circuitws. The high voltage for the B+, the 6v for the heaters, the 5v for the rectifier heater, maybe a bias supply winding. All those are secondaries.

There is no polarity to AC voltage, by its nature. If you connect two windings together then you need to concern yourself with relative phase, but you do not have that here.

The expected voltages? When not connected to the circuits with tubes, the voltages will be higher than normal. But nominally, ther will be 6.3vAC (they are ALL AC voltages)for the tube heaters, there will be 5vAC for the rectifier tube heater (not all transformers have this one), there will be a high voltage winding of several hundred volts. Sometimes ther is a bias supply winding of anywhere from 20v to 70v. Obviously you cannot read the 5v winding on the 6.3v wires. Each winding is independent.

[Tom Phillips]

Billy,
I think it would be a good idea to study a bit about how transformers work. Google Power transformer Tutorial, how transformers work etc and you will find lots of information. One example is Electrical Transformer Tutorial - YouTube
This will help you understand more about what is going on with your transformer.
The link is just one example. I'm sure you can find much more plus the information in basic electronics books.
Cheers,
Tom

[J M Fahey]

I got continuity on the following, but 0 resistance:
22awg Black with White/B
all 22awg Red with Red with Yellow w/R

1)This does not make sense.

2) What do you call "zero resistance"?

3) What do you actually read on the screen in each case?
What resistance scale are you using in that precise moment?

4) What happens if after measuring what you call "zero resistance" you touch probes to each other?

5) What if now you separate probes in the air, touching nothing, nor each other?

Thanks.

[Jazz P Bass]

This guy is gonna kill himself. (or wreck the amplifier)
Messing with the mains wires, no idea which wires are what.
Please take the amp to someone that knows what they are doing.

[Billyaxe]

B-15N Power Transformer

This guy is gonna kill himself. (or wreck the amplifier)
Messing with the mains wires, no idea which wires are what.
Please take the amp to someone that knows what they are doing.

Well thanks everyone, but I think this has gotten beyond my novice ability to change the transformer. If only the wires were the same colors I could just change it. I cant take a chance on blowing this transformer up, it costs over $100 to replace. I thought I was close with only 3 wires to identify. I guess I'll find somebody.
I was trying to measure resistance using an impedence tester (used for speakers). I was getting no reading. Thats what I mean when I said 0 resistance. --Billy

[J M Fahey]

I was trying to measure resistance using an impedence tester (used for speakers). I was getting no reading. Thats what I mean when I said 0 resistance.

Sorry but "no reading" means you didn't measure, that you left the meter somewhere else, turnedd off and unconnected.

*If* you connected its probes to the transformer, *anything* appearing on the scale or screen *is* a reading and has a meaning.
Zero is a reading.
Infinite/open is a reading.
Out of scale/overflow is a reading.
All mean different things, but we don't know which one applies, so we are in the dark.

By the way, what is an "impedance tester"?
Does it have a brand, model?
Can you link to it?
Thanks.

[Enzo]

SOmeone used to sell them as a hand meter, but I do still find these:

Tenma Speaker Measurement Interface / USB Woofer Tester | WT2 | Tenma

Dayton Audio DATS Dayton Audio Test System 390-806

This isn;t what I remember, but is the general idea:

Tenma Audio Impedance Meter | 72-6948 (726948) | Tenma

Fancier:

Impedance Meter for Testing of 70V/100V Distributed Systems

Of course he may have something totally different in mind. And then there are also the $700-800 ones.

[Billyaxe]

B-15N Power Transformer replacement

I used a Tenma audio Impedence Tester Model 72-6948. I got this so I could test speaker cabinets at gigs to see if they were 4, 8, or 16 ohms. So I'm not sure if this is even the correct tester for what you all ask me to test. The other resistance tests I tried were with a regular cheap volt/ohm meter and I either so the meter pinned or didnt react at all.
Can anyone tell me in the simplest terms how I can test the transformer to determine the mains? --Billy

SOmeone used to sell them as a hand meter, but I do still find these:

Tenma Speaker Measurement Interface / USB Woofer Tester | WT2 | Tenma

Dayton Audio DATS Dayton Audio Test System 390-806

This isn;t what I remember, but is the general idea:

Tenma Audio Impedance Meter | 72-6948 (726948) | Tenma

Fancier:

Impedance Meter for Testing of 70V/100V Distributed Systems

Of course he may have something totally different in mind. And then there are also the $700-800 ones.

[Billyaxe]

So I have 3 wires left on this transformer that havent been identified. Can anyone tell me how to test these to determine where they go? --BIlly

I used a Tenma audio Impedence Tester Model 72-6948. I got this so I could test speaker cabinets at gigs to see if they were 4, 8, or 16 ohms. So I'm not sure if this is even the correct tester for what you all ask me to test. The other resistance tests I tried were with a regular cheap volt/ohm meter and I either so the meter pinned or didnt react at all.
Can anyone tell me in the simplest terms how I can test the transformer to determine the mains? --Billy

[Prairie Dawg]

The other way to do this is to use a variac to apply a low AC voltage to the primaries and see what comes out.

[g1]

If you carefully re-read the entire thread, you will see that all wires have been accounted for.

1. The two reds on the new transformer = the two reds on the old
2. The new wire you list as “yellow w/red stripe” is probably meant to be red with a yellow strip and equals your old red with a yellow strip.
3. The new green and new “white w/green stripe” are the 6.3 volt heater winding and equal to your old two greens.
4. The new yellow and new “white w/yellow stripe” are the 5 volt heater winding and equal to your old two yellows.
5. The new black and new “white w/black stripe” are the primary winding and equal to your old two blacks.

Yellow/red goes where red/yellow was, standby switch.
Black to fuse
White/black stripe to ground switch.

[Randall]

This guy is gonna kill himself. (or wreck the amplifier)
Messing with the mains wires, no idea which wires are what.
Please take the amp to someone that knows what they are doing.

plus one on that!

[Tom Phillips]

Billy,
I think you should follow my idea in post #17. It's a whole new (and better) game when you understand the theory.
Regards,
Tom