Smoking Transformer

[JBLoudg20]

Hey all,

I have been working on my latest project, and right off the bat Ihave hit a snag. I am using a Hammond 183K12 to power the heaters of 2 6AS7G and 2 6SN7. I Connetect the transformer as follows: (the bottom transformer is my Hammond 269AX for the PSU section)




When I turned on the power, the transformer started smoking, and I quickly cut power. I disconnected everything from the secondaries, and turned it back on to test the voltage, and unfortunately I got zero. I have ordered another transformer, but I'd like to knwo what I did wrong. I am about 99.9% sure I wired it as shown by my drawing.

Any ideas? Thanks in advance.

[jleaman]

Originally posted by JBLoudg20
Hey all,

I have been working on my latest project, and right off the bat Ihave hit a snag. I am using a Hammond 183K12 to power the heaters of 2 6AS7G and 2 6SN7. I Connetect the transformer as follows: (the bottom transformer is my Hammond 269AX for the PSU section)




When I turned on the power, the transformer started smoking, and I quickly cut power. I disconnected everything from the secondaries, and turned it back on to test the voltage, and unfortunately I got zero. I have ordered another transformer, but I'd like to knwo what I did wrong. I am about 99.9% sure I wired it as shown by my drawing.

Any ideas? Thanks in advance.

What is the brand what does it look like ? Maybe you can request a drawing diagram to connect it to the ac voltages you need.. I have seen some people buy a 110V ac tranny and use 220 buy mistake. We can help you if you can provide details of make model etc etc

[anatech]

Hi jleaman,

I am using a Hammond 183K12 to power the heaters of 2 6AS7G and 2 6SN7.

JBLoudg20,
Your diagram is okay. How fast did you say it smoked? I assume you did check the heater currents against the Hammond's ratings. I haven't yet. You always leave some headroom there.

But even still, I've not seen a transformer smoke quickly unless it's high current and the winding is shorted. The hum would tip you off first I'd think.

-Chris

[jackinnj]

i have been doin' this for 40+ years and have never made a trannie smoke -- even through the thick and thin of many catastrophes in audio, ham radio and physics labs which destroyed several transformers (I burned out the transformer in my Eico 753 Tri-Band transceiver when I keyed down on 20 meters for too long -- rewound the transformer !)

[tubelab.com]

If you accidentally wire the two parallelled primaries so they are out of phase, the transformer will smoke immediately! Don't ask me how I know this. If the power wasn't on long, there may still be some life left in it. I woudn't use it in an amp, but I would try again before you smoke the new one.

If you look at the diagram on Hammonds web page you will see a small dot next to one of the pins on each winding. Whenever two windings are connected in parallel the pins with the dots are connected to each other, and the pins without the dots are connected to each other. For this transformer, connect pins 1 and 4 together. Connect 3 and 6 together. Connect power to the 1-4 pair and to the 3-6 power. Test for voltage with no load. If you have voltage, then try it with a load.

[jleaman]

Originally posted by tubelab.com
If you accidentally wire the two parallelled primaries so they are out of phase, the transformer will smoke immediately! Don't ask me how I know this. If the power wasn't on long, there may still be some life left in it. I woudn't use it in an amp, but I would try again before you smoke the new one.

If you look at the diagram on Hammonds web page you will see a small dot next to one of the pins on each winding. Whenever two windings are connected in parallel the pins with the dots are connected to each other, and the pins without the dots are connected to each other. For this transformer, connect pins 1 and 4 together. Connect 3 and 6 together. Connect power to the 1-4 pair and to the 3-6 power. Test for voltage with no load. If you have voltage, then try it with a load.

Id also try it with a variac too. Power it up slowly

[JBLoudg20]

Originally posted by anatech
Hi jleaman,


JBLoudg20,
Your diagram is okay. How fast did you say it smoked? I assume you did check the heater currents against the Hammond's ratings. I haven't yet. You always leave some headroom there.

But even still, I've not seen a transformer smoke quickly unless it's high current and the winding is shorted. The hum would tip you off first I'd think.

-Chris

It didn't hum at all, which I thought was strange. The transformer is rated at 8.8A, and mt tubes should draw about 6A of current, so I should be ok there.

Originally posted by tubelab.com
If you accidentally wire the two parallelled primaries so they are out of phase, the transformer will smoke immediately! Don't ask me how I know this. If the power wasn't on long, there may still be some life left in it. I woudn't use it in an amp, but I would try again before you smoke the new one.

If you look at the diagram on Hammonds web page you will see a small dot next to one of the pins on each winding. Whenever two windings are connected in parallel the pins with the dots are connected to each other, and the pins without the dots are connected to each other. For this transformer, connect pins 1 and 4 together. Connect 3 and 6 together. Connect power to the 1-4 pair and to the 3-6 power. Test for voltage with no load. If you have voltage, then try it with a load.

Well, I may actually have made a mistake then. I ran jumper wires from one 6AS7G to one 6SN7. I then did the same thing wit the other set of tubes. Then I ran one winding of the secondary to one of the sets, and the other winding to the other set. However, the windings were never run to each other, so I doubt they were out of phase.

[jamesjung21]

If you look at the diagram on Hammonds web page you will see a small dot next to one of the pins on each winding.

How about in the case when I have to connet them in series..? Does it really matter which way I connect them together (do I have to connect the dotted pins together and use the two un-dotted pins for primary input...?)

The dots are also present on some vintage potted HP transformers...

Thanks,
James

[SY]

Does it really matter which way I connect them together in series..?

Yes.

[jamesjung21]

Yes.

So, does that mean I have to connect the dotted pins together and use the two un-dotted pins for mains input...?