What Happens When a PT Fries?

[The New Steve H]

What happens when a power transformer craps out? Does it just short and blow the main fuse?

I'm wondering because my latest amp is running hotter now that it's in a cabinet. The end bells are too hot to touch for more than a second. I don't know if it will ever get hot enough to blow, but I figured I'd ask about it.

Wondering if I could improve it by strapping a heat sink on it.

[Reeltarded]

What happens when a power transformer craps out?

A kitten dies.

Umm.. WHOA. You have a current draw problem... oh wait... can you measure the temp? Is the amp dimed and you play and then it's raging hot, or just idle and it's hot?

[Jana]

A kitten dies? And then they give off a pungent odor--"Oh smelly cat, what have they been feeding you?"

Any transformer that is too hot to touch is too hot to touch.

[The New Steve H]

The amp has a PPIMV. I generally play with the preamp turned to 1/2-3/4 of full power, and the PPIMV is at around 1/2. It was on for around an hour. I'm using a single 12" 8-ohm speaker, which makes me wonder what would happen on the 4-ohm tap with two speakers.

It's my understanding that these things are rated to about the boiling point of water, and I don't think it's that hot. I don't have an IR thermometer, or I'd give you the actual figure.

People who follow my adventures will recall that I bought this PT before I learned that 6BM8s suck huge current.

[surfsup]

What is the PT rating? It looks like a 6bm8 pulls around 40mA at idle for both halves. That doesn't seem like a ton of current.

[The New Steve H]

It's a 100 mA PT running four tubes. The triodes are not hooked up.

[John_P_WI]

A small dc muffin fan like that used in a computer will go a long way to keeping things cool....

[Phil_S]

If you use a fan, make it an exhaust fan.
To keep fan noise down, a trick is to get a fan you can run a half it's rated voltage (12VAC fan run off the filament winding at 6VAC) and half speed.
Cut a vent in the cab.
The triodes don't contribute that much heat. Some guys are able to pull them while still hot.
Too hot to touch isn't a problem. Put a temp meter on it and see just how hot it really is. 125F hot water will burn you. You can't judge by touching. I'd say you are pushing your luck at around 160-180F.

[Phil_S]

To answer your original question, when a PT blows, you can see it let the smoke out. The smoke can be just a faint wisp. The smell can be short lived and not much of anything, or it cold be stinky. Depends on the PT and what exactly went on. In either case, it happens at super speed. It will be over before you know it. I"m not going to tell you how I know so much, so please don't ask.

[katopan]

Someone had to mention a cat! I will never forget the smell of the one at work that found it's way into the nice cosy switchgear enclosure and draped itself across two 415V busbars.

Too hot to touch for 1 second is too hot. It might work OK but won't last the distance, especially if you then use it on the elevated temperature of a stage.

[surfsup]

I read 18w and immediately had teo tubes on the brain...do you mind posting what's your ot impedance, plate voltage and cathode resistor value?

[The New Steve H]

The plate voltage is around 300. I have two 8.5K OTs in parallel. The output tubes feed into about 200 ohms of cathode resistance.

I think I'll just play it until it explodes.

I keep having this neurotic fear that I actually grabbed the rectifier tube instead of the PT. I don't think I'm quite that stupid, but I will check tonight.

[The New Steve H]

I may actually be that stupid. Tonight after an hour or more, I could put my fingers on the PT for several seconds.

[Reeltarded]

Goof!

Go play, and God sakes not in traffic!

[rp]

A kitten dies.

Good God, be careful!