concert lead problem

[DavidGiandiletti]

just made my first sunn purchase, i got a silver face concert lead and 612s cabinet in pretty much perfect condition. When i first plugged it in the distortion wasn't working and the pots were really scratchy, i cleaned the pots with deoxit and got it working great except for the distort feature, when i turn it up it very, VERY subtly sounds a little more saturated but not anywhere near what i would even consider calling distortion. Any clues on what the problem could be or how expensive it would be to fix it? If its too much i would be happy just using the clean, this thing sounds great with pedals.

Thanks!

[DavidGiandiletti]

Also..as most of you know the cab is 6ohms would it be safe to run a 4 ohm tube head into it? I've heard with tube heads its better to have a perfect match.

[Isaac]

I wouldn't hesitate to run a tube head into the 612S, with the impedance set at either 4 or 8 ohms. Others' opinions may vary.

[JoeArthur]

I wouldn't hesitate to run a tube head into the 612S, with the impedance set at either 4 or 8 ohms. Others' opinions may vary.

Yep, but my opinion doesn't vary. 

The whole concept of "must have exact matched impedances" for tube amps is only for maximum power transfer. It's a delusion at best - some people realize that "matched" can only be nominal at best and that real impedances vary all over the map. 

Go for it and consider the choice of 4 or 8 ohms to be nothing more than an additional tone choice (i.e. if you do have a selection, set it to what sounds better to you).

[DavidGiandiletti]

ok i've always heard that the impedance of the head should always be less but i guess when its only two ohms off its no big deal, I definately have some experimenting to do. any clue on the problem with the head?

[mckinnon audio]

  Hi Dave,for your distortion(or lack of distortion) try this.Check the fet (field effect transistor) just before the distort. control.On the schematic it's Q-202,it's real # is 2N4304,and check the resistors and solder connections in the surrounding area.Hope this is of some help,Mel.

[JoeArthur]

  Hi Dave,for your distortion(or lack of distortion) try this.Check the fet (field effect transistor) just before the distort. control.On the schematic it's Q-202,it's real # is 2N4304,and check the resistors and solder connections in the surrounding area.Hope this is of some help,Mel.

I just had a thought - are you using a footswitch for the distort? If not, that's your problem as the distort is "off" without the footswitch (or something like a shorting plug) completing the ground connection.

[DavidGiandiletti]

Ok, I have the footswitch but havent tried it since i cleaned out the pots. If that doesnt work I'd like to take a look at the electronics but dont really know what I'm doing. Is there as much of a danger working with solid state amps as there is with tube amps?

[JoeArthur]

Ok, I have the footswitch but havent tried it since i cleaned out the pots. If that doesnt work I'd like to take a look at the electronics but dont really know what I'm doing. Is there as much of a danger working with solid state amps as there is with tube amps?

I could kill you with a solid state amp. 

Turn the power off and play it until you hear no more sound. Thankfully, solid state doesn't need heaters to work and this will drain the caps.

But as I said, the distort doesn't work without something making the connection to ground... like a footswitch. Conversely, the "boost" is always on without a footswitch to turn it off.

(edit) Oh, and of course the reverb is always on as well.