Evil Twin (a.k.a.) red knob twin

[realrocker]

Hi everyone,

I just recently obtained the fender red knob twin. Now let me tell you, everything said about it is true, heavy, and loud. However, as good as it sounds i get natural tube distortion when it isn't even that loud. It is not extremley clean. Does anyone know wat can be causing it. It's in perfect condition, and the tubes are chinese crap but there is no use. This is my first tube amp, so i know about tube distortion. But it is doing it before i even turn the volume to 2. Is it a tube problem, bias, ohms? Help plz. If it helps, two of the power tubes don't glow at all, the other two glow a nice orange as the should, so plz help me out. Thnx

-Matt

[Enzo]

By glow, do you refer to the heater in the center of the tube? If two of your power tubes are not heating, then there is your problem.

If you mean by glow that the metal structure inside the tube is glowing red hot in spots, that is bad, but would also be the problem.

What you want is that little thing right in the center glowing orange, just like there are two of them in each small tube.

If two tubes are dark, then the heater curent is not getting to them. If two tubes are getting red hot, then they have lost their bias, either due to a circuit faulure or a tube failure.

[realrocker]

actually, i checked the bias, and it is set rite, at 0.04v. and they are glowing a nice orange color, but i took them out and they fell apart so that was my problem. they were sixteen year old chinese tubes, so i bargained the the store manager to give me two matched pairs of fender branded russian tubes; and i gotta tell you, the amp sounds amazing on the clean channel with that classic tank rev. Thanks for your help though!

[canadianrangervett]

late 80's red knob twin

Im sorry for posting through a reply thread.. having trouble navigating.. I just picked up a red knob twin guessing its about an 89-91 model.. the problem is... to get the volume, and I mean a low volume but enough to rehearse in a small room I have the amp on 7 volume wise.. I put in a set of new tubes samie same..cant get any volume.. also it seems to be decaying volume wise sometimes..help me please.. love this amp... but Im in Korea... difficult to get anything done here.. cause the look at it and say " I dont know Fender " and they wont even look at it..
Thanx
Harold

[PRNDL]

After bad tubes, the most common cause is the amp needs a "cap job", which would be about right for its age.

Check with the store to see if they have an amp tech that can do this and ask how much you will be charged.

Did they let you play it loud in the store?

[canadianrangervett]

red knob twin

hey.. and Thanx..
I have a new cap kit.. but I got it off ebay.. so I kinda have to match the caps as I put them in.. they are all the correct value.. but some of them seem a little bit smaller... I played the crap out of the amp in the shop and it worked well.. but.. it started to lose volume a couple of weeks or so ago.. so I put the new tubes in it...played a gig 2 weeks ago.. couldn't get a lot of volume.. and it started to distort .. even at low volume.. I will try putting in the new caps and see what happens...if you can think of anything else please, let me know..
Harold