Shorting the secondary...........

[axepilot]

Just out of curiosity, what happens if you short the speaker outputs on a tube amp - dead short on the OT secondary?

We all know that the OT's can live with lower impedances, but how about dead shorts?

I imagine bad things, but what says the learned here?

[Old Tele man]

...it's "reflected" back to the primary as a "short" but vacuum tubes, especially pentodes, actually "LIKE" a 'short' far more than an 'open,' which can cause "high-voltage" flyback conditions that arc both tube and OT.

[axepilot]

I know that "flyback" is bad juju.........................I was just wondering what a dead short would do. I don't see any good coming from it..........

[Old Tele man]

I know that "flyback" is bad juju.........................I was just wondering what a dead short would do. I don't see any good coming from it.............to continue your thought: SHORT does LESS damage than an OPEN will.

[El Caballo]

My speculation: the OT has internal resistance, especially to AC, so it will dissipate as heat all the energy that your speakers would normally put out as sound. Eventually the heat will melt some insulation and you'll have a problem.

However, this will take a lot longer than frying it with flyback pulses from an open circuit. This is why Hiwatt wired their output jacks to short the OT if nothing is plugged in. I did the same thing with the head I built.

Someone please correct me if I'm wrong.

[Old Tele man]

This is why Hiwatt wired their output jacks to short the OT if nothing is plugged in. ...Leo Fender and companies do the samething with most of their amps...although during CBS-era there were a couple amps that had Z-switching configurations that did not short out when no speaker was connected.

[JJman]

2/4/8 ohms is pretty close to zero when you compare how far they are from infinity.