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Thread: B-15N Power transformer replacement

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    B-15N Power transformer replacement

    Hello, I've acquired a replacement PT for my B-15N but the wire colors don't match the existing PT.
    The replacement acquired on ebay from DBHarmony has no paperwork or brand name just a series of numbers 300708-1 89300030 and E.I.A. 682 0434. Can anyone help to identify this PT so maybe I can track down its manufacturer for a diagram? Or any suggestions how to procede? --Billy

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    Lifetime Member Enzo's Avatar
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    Does the seller have no documentation to share? Will the seller tell you where the thing came from? Did the seller claim it was a replacement for your model amp, or just for amps in general?

    What wire colors do you have now? Use an ohm meter to determine which wires are related. Windings with heavy wires and measureing less than an ohm should be heater windings.

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    Manufacturer is electrical windings, now called TMI
    Transformer EIA codes

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    The seller says he has no documentation, and claims it is a replacement. For those who know about B-15N's the power transformer doesnt fit other models (as far as I have heard).
    The power transformer is E.I.A. #682 which I did find out is made my TMI (formerly Electrical Windings).

    The old Transformer's colors are pretty simple: 2 yellows to a 5AR4 Tube, 2 Reds to another 5AR4 tube, 2 Greens to a 6L6GC tube, Red w/yellow stripe to standby switch, a black to a grounding switch, and a black to the 3 amp fuse.
    The new transformer also has 9 wires: 2 reds, yellow, yellow w/red stripe, white w/green stripe, white w/yellow stripe, white w/black stripe, Green, and black
    I've done minor electronics and can solder but can you explain further how to test the resistance and explane the what the heater windings are. Thanks for alll the help. --Billy

    Quote Originally Posted by Enzo View Post
    Does the seller have no documentation to share? Will the seller tell you where the thing came from? Did the seller claim it was a replacement for your model amp, or just for amps in general?

    What wire colors do you have now? Use an ohm meter to determine which wires are related. Windings with heavy wires and measureing less than an ohm should be heater windings.

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    Lifetime Member Enzo's Avatar
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    Heaters (also called filaments) are the glowing things inside every tube.

    Your old transformer had the standard wire colors:
    yellow - 5vAC for the rectifier tube heaters
    green - 6.3vAC for the other tube heaters
    red - high voltage - several hundred volts AC
    red w/ yellow stripe - center tap of high voltage winding (often written as r/y)
    black - primary (your 120v mains from the wall outlet)

    Like its schematic symbol suggests, each of these wire groups are a winding of wire inside the core of the transformer. SO if you just had all those wirs sticking up in the air, you would find with your ohm meter that some are connected to others. Specifically the two greens are connected together, the two yellows are connected together, the two reds together with the r/y also, and the two blacks together. And you will also find that none of the groups are connected to any of the others. None of the reds are connected to the greens or the yellows, the blacks to none of the others etc. If any of those rules are violated, the transformer is probably bad.

    Not everyone uses the old color code these days, especially in other countries, but even in the USA, we find for example the 6.3v wires on most Peavey amps are yellow rather than green. SO your new transformer is one of these. SO in the absence of data, I'd get out my ohm meter, and pick a wire. Clip one meter probe to the wire. Now touch the other probe to each of the remaining wires, one by one. Note which other wires it shows a connection to on a paper. Mark that wire somehow - tape, bend it, knot it, whatever. pick the next wire and see what it connects to. Go through all of them, you listed 9, and see which ones connect to which others. And take note of the resistance.

    Heater wires will be heavier wire usually, but they will have a very low resistance, probably less than an ohm. But the high voltage might read 200 ohms or more.

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    Old Timer Tom Phillips's Avatar
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    Quote Originally Posted by Billyaxe View Post
    The seller says he has no documentation…
    That’s a really lame transformer company or more likely a really unhelpful employee who answered your question.

    Quote Originally Posted by Billyaxe View Post
    The old Transformer's colors are pretty simple: 2 yellows to a 5AR4 Tube, 2 Reds to another 5AR4 tube, 2 Greens to a 6L6GC tube, Red w/yellow stripe to standby switch, a black to a grounding switch, and a black to the 3 amp fuse.
    The new transformer also has 9 wires: 2 reds, yellow, yellow w/red stripe, white w/green stripe, white w/yellow stripe, white w/black stripe, Green, and black…Billy
    My take is this:

    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.


    Edit: And I see that I was typing while Enzo was answering and he has explained how to Ohm out your windings.

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    Last edited by Tom Phillips; 04-20-2013 at 02:22 AM. Reason: additional comment

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    Supporting Member Jazz P Bass's Avatar
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    Make these measuremnets with the power OFF, please.
    Enzo did note "resistance maesurements'.
    Pedantic am I.

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    Lifetime Member Enzo's Avatar
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    Yes, no power during resistance readings.

    My mental image was of the new transformer not yet wired, since he had no idea which wire was which. But I should not assume...

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    B-15N Power transformer wiring

    Thanks guys and Enzo for putting things in simple terms so I can learn along the way. The transformer I am testing is the new one not hooked up. The old one is still in the amp.
    I did testing with a continuity tester and also with an impedence tester. Here's the ones that matched impedence wise:
    16awg Green with 16awg White/G at .7 ohms
    16awg White/Y with 22awg Yellow at .3 ohms

    I didnt read 200 or so ohms on anything as you expected, so dont know what would be the high voltage wires. I would guess the reds, but is there anyway I can be closer to sure?

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

    So Enzo, with this info can I assume you are right that I can use the greens, yellows (even though one is 22 guage), and reds in place of those respective colors on the old PT?
    If so, my next questions will be:
    I need a wire each to a Standby switch, a grounding flip switch, and a 3amp fuse.
    I'm not sure how the Yellow w/R relates as a third wire to the red?

    Many thanks for the help on this. --Billy

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

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    B-15N Power transformer wiring

    Quote Originally Posted by g-one View Post
    Yellow/red goes where red/yellow was, standby switch.
    Black to fuse
    White/b to ground switch.
    Okay thanks. It looks like I have everything I need to wire up the replacement. Any second opinions out there? Enzo, you ironed out the first 6 wires for me, does the last three agree with you? Thanks to all for the help. --Billy

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    Lifetime Member Enzo's Avatar
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    I deal with it conceptually. If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages. I trust my fellow posters in this thread.

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    Old Timer Tom Phillips's Avatar
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    Quote Originally Posted by Enzo View Post
    .. .If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages...
    That’s the verification test you need to do to determine if the transformer is correct for your amp. Especially to clear up the following:

    Quote Originally Posted by Billyaxe View Post
    16awg Green with 16awg White/G at .7 ohms
    16awg White/Y with 22awg Yellow at .3 ohms
    …I got continuity on the following, but 0 resistance:
    22awg Black with White/B
    all 22awg Red with Red with Yellow w/R
    Because it doesn’t make sense that you got the .7 and .3 Ohm readings on the low voltage windings but then got “0 resistance” on the high voltage winding.

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    Quote Originally Posted by Tom Phillips View Post
    Because it doesn’t make sense that you got the .7 and .3 Ohm readings on the low voltage windings but then got “0 resistance” on the high voltage winding.
    Yes, that's one of Enzo's pet peeves, “0 resistance” meaning zero ohms or no reading open circuit or out of range.

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    B-15N Power transformer wiring

    Quote Originally Posted by Enzo View Post
    I deal with it conceptually. If you have found the primary wires, apply mains voltage to it and see if the wires make the desired voltages. I trust my fellow posters in this thread.
    Oh I thought I was very close to solving this, hopefully it's still within my ability based on your instructions. Sorry I have to ask for simple terms.
    So when you say 'primary' that would be where 110 volts would be applied, right? Did I indicate to you, by what I described, that I found the primary wires?
    If I know what those wires are, am I applying a hot and neutral and does it matter which is which? Then these 'desired voltages' would be read on the heater wires? And how do I know what voltages they are?
    Thanks --Billy

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    Lifetime Member Enzo's Avatar
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    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.

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    Old Timer Tom Phillips's Avatar
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    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

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    Last edited by Tom Phillips; 04-27-2013 at 06:45 PM.

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    Old Timer J M Fahey's Avatar
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    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.

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    Supporting Member Jazz P Bass's Avatar
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    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.

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    B-15N Power Transformer

    Quote Originally Posted by Jazz P Bass View Post
    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

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    Old Timer J M Fahey's Avatar
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    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.

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    Lifetime Member Enzo's Avatar
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    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.

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    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

    Quote Originally Posted by Enzo View Post
    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.

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    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

    Quote Originally Posted by Billyaxe View Post
    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

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    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.

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    If you carefully re-read the entire thread, you will see that all wires have been accounted for.
    Quote Originally Posted by Tom Phillips View Post
    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.
    Quote Originally Posted by g-one View Post
    Yellow/red goes where red/yellow was, standby switch.
    Black to fuse
    White/black stripe to ground switch.

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    Supporting Member Randall's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    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!

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    Old Timer Tom Phillips's Avatar
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    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

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    Last edited by Tom Phillips; 06-02-2013 at 07:28 AM.

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