Orange Amps Forum

Hi folks,

First off it's my first post, so happy to meet you all, and hopefully someone can give me some pointers.

I have a Dark Terror head going into a 1x12 Orange cab, and up until this morning everything has been sweet. Both are just over a year old.

My issue : all of a sudden I get no sound at all from the amp when I go from Standby into either 7w or 15w mode. The speaker and speaker cable are both OK, I have checked them with another amp I have. The 2 power tubes are still glowing. I also tried plugging directly into the return of the effects path, but no joy.

Cheers for any advice.

Did you check the HT fuse?

Nope, not yet, thanks.

I see I can screw it out from the back. Can you see then if it is blown or not? I have a multimeter about so I could check for continuity etc. I guess it is blown then it will just blow again if I put in a new one, i.e. the cause could be a bad tube maybe?

Thanks.

OK, i just pulled the fuse and is indeed blown, no continuity with a multimeter. Changed it to a new one which I luckily had around, and its all sounds again. Thanks for the advice man.

I am still wondering though what caused it to blow, maybe I have a dodgy tube.

Could very well be a bad tube but it will be hard to know unless the fuse blows again.

On the other hand, could have been some sort of power issue that the fuse protected the amp, too. To be on the safe side, it wouldn't hurt to have some spare tubes ready...

And welcome to the forum!

Thanks guys.

Must say I'm enjoying the Dark Terror, I also have a Mini Rec and it gets nowhere near the tone.

I had exactly the same issue late last year. The cause was a failed or failing EL84 tube in the power section in my Dark Terror. The amp circuit was “saved” by the fuse (that you found blown). Since I did not have spare fuses around, I sent it to the vendor at a cost to me for shipping and tubes.

I made sure That now I keep a few fuses around and a set of backup tubes....especially the EL84 pair
....handy should one of the pair fail again.

Welcome to the Orange forum!


adkguy07

Tubes have lots of different failure modes.

They can just wear out -- get duller sounding, breakup earlier.

Internal connections can break -- still light up but no sound.

They can lose vacuum, turn white inside, and stop working.

The heater filament can physically sag, and then bump up against things it shouldn't, and cause a short circuit. The deformation can be bad enough that the filament always touches something, or it can be a minor sag that only touches when random vibrations get it flapping in the wrong direction.

I think that last thing is what you've got. The bad tube might never short out again, or it might do the same intermittent thing, or it could short out permanently.

I'd toss both power tubes and replace them.

I wouldn't play the amp with the current tubes. Fuses usually protect the amp, but sometimes they don't blow fast enough. Most techs have horror stories about catastrophic damage where everything melted except the fuse.

DT is cathode bias, so plug'n'play.

If the heater element shorted and blew a fuse why would the power tubes still be glowing...

Sooner wrote: ↑

Sun Jun 16, 2019 9:31 pm

If the heater element shorted and blew a fuse why would the power tubes still be glowing...

Because the heater circuit is separate from the HT and it only takes 500 milliamps to blow the HT fuse so it would go first.

Jondog wrote: ↑

Mon Jun 17, 2019 12:12 pm

Sooner wrote: ↑

Sun Jun 16, 2019 9:31 pm

If the heater element shorted and blew a fuse why would the power tubes still be glowing...

Because the heater circuit is separate from the HT and it only takes 500 milliamps to blow the HT fuse so it would go first.

It's the separate circuits that makes me wonder. How does a surge in current on the low voltage output side of the PT create s surge on the high voltage side?

Sooner wrote: ↑

Mon Jun 17, 2019 2:22 pm

Jondog wrote: ↑

Mon Jun 17, 2019 12:12 pm

Sooner wrote: ↑

Sun Jun 16, 2019 9:31 pm

If the heater element shorted and blew a fuse why would the power tubes still be glowing...

Because the heater circuit is separate from the HT and it only takes 500 milliamps to blow the HT fuse so it would go first.

It's the separate circuits that makes me wonder. How does a surge in current on the low voltage output side of the PT create s surge on the high voltage side?

I personally haven’t experienced it in a tube, I’m relating it to other electrical circuits I’ve worked on, but he's saying the heater circuit touched the tube anode or plate etc.. That would connect them.

Jondog wrote: ↑

Mon Jun 17, 2019 2:25 pm

I personally haven’t experienced it in a tube, I’m relating it to other electrical circuits I’ve worked on, but he's saying the heater circuit touched the tube anode or plate etc.. That would connect them.

I see. Seems like that would be catastrophic even if momentary.