Does it hum with nothing plugged into Input?

-Jon

(edited for bloody spelling...)

Well, it could be microphonic tube or Korean pick-up as these pick-ups are known to feedback like crazy, especially with heavy distortion.

-Jon

Marcus,
You are in no danger changing a pre-amp tube or working on the reverb cables.

I live in the High Volt lethal interiors, so I can let you know the how and why of that.

Nice post Andy! (Howdy to ya...)

-Jon

Did it work?

Jon

The Peavey 5150 is problematic in my experience- unless noise and a certain ampount of harshness is not a problem for you.

IMHO is a goofy design. Damn shame as Peavey was well-designed and very reliable in the 70's and 80's. Now you may as well buy a Crate.

Just speaking from experience,
Jon

Assemble a clip lead with a 240 Ohm to 1K 5 to 10W resistor in series with one end, insulate lead on end without resistor. Clip resistor-end to chassis and then clip other, isulated, end to filter cap of your choice. (Orange amps have no standby so you're OK with these instructions. (Lack of Standby...

Try changing pre-amp tubes as micro-phonic tube could cause ringing and if it had a badly displaced element it could also call humm.

-Jon

Good and simple advice from acorkos. This is probably the quickest way.

Generally speaking the low-ohm resistance side will be the input, assuming you Ohm-it-out...
Jon

Forget WD-40. Use DeOxit-5 for best results. This is the Pro stuff.
I don't know if it can be shipped to the U.K. but it's the best-of-breed.

(I use it in all critical applications. Made in the USA and I get it shipped to me with the usual costs for hazarous material.)

-Jon

Well, "let's get technical": You have to double the speaker load as the Output Transformer interrupts the Plate Impedance of the output tubes in relation to the Turns Ratio of the OutPut Transformer to the Speaker Impedance. Thus in removing two of the four output tubes you double the Output Impedan...

Forgot to mention that you won't have much volume reduction as it'll only be 3Db- and this is what we are taught to understand as the MINIMUM the human ear can discern as a difference in volume level. Forget "power tube break-up". By the time the power tubes break-up you'll be deaf and yer ears will...

Here it's speaker rating = output rating X 2, at a minimum.

The classic engineering rule-of-thumb is 3X power-rating for everything.

-Jon

2 X 8 = 4 Ohms, DON'T DO IT!

-jON

Agree wil probable Ground Loop-

-Jon

EVERY Orange I've seen is BETTER than every Bogner I've seen- and I've been inside lots of both.

Go with the Orange...

-Jon