[Uptown Audio]

It's a cathode biased amp. There is no adjustment. 

Guys, we don't need to be encouraging someone who doesn't know what an output tube is to be poking around inside of a tube amplifier. He might get himself killed.

Not to be condescending, but I'd take Jake and my advise and keep your hands outta there. Not only could it ruin your day, it could ruin your amp. You are going to need to buy new tubes anyway. Just pack it up, send it to Rogue and let them test and repair it. You will be much better off and so will your amp. They are not going to rape you.
-Bill

[usp1]

Richidoo- Thanks. I thought this amp was self biasing. Does that make a difference? Also I found that the amp is a .75 amp slow blow fuse. It has only one of those on the circuit board so it should be cheap to try and see if replacing that can do the trick.

[usp1]

Bill,

I am just as concerned about my safety as you are...although not sure which is worse killing myself or the amp!

I think the fuse is the simplest thing to try and I will do so with the utmost caution. Otherwise off it goes to Rogue.

[richidoo]

Richidoo- Thanks. I thought this amp was self biasing. Does that make a difference? Also I found that the amp is a .75 amp slow blow fuse. It has only one of those on the circuit board so it should be cheap to try and see if replacing that can do the trick.

Yes it does make a difference. According to Bill it is fixed bias, so you can't test the tube with the amp. 

Replace the fuse, if it blows again, get a new set of power tubes and replace the fuse again. Since it's a used amp, they could be just failing from age. 2000 hours is all you can expect, about once a year if you listen a lot. Find someone to test the oldies for use as spares.

It is important to learn how to maintain your tube amps. If you have to mail it in every time something goes wrong you will just mail it to the next buyer instead. Have fun!

[usp1]

I will do so. I need to find a good reference to start learning more about tube amps.

[usp1]

OK...I think I fixed it. It was the fuse on the circuit board (B+ fuse?). I had to replace it twice before I realized what the problem was. After the second new fuse blew I noticed a small black object on the circuit board. Closer inspection showed a tiny screw that was shorting two component leads.

It was one of the screws that holds the cover which, the previous owner had told me had gone missing! It must have fallen in the case when he lost it and must have moved around sometime during transportation to eventually get into a place where it was short circuiting something. I guess ( or at least hope) I was fortunate it did not do any lasting damage.

Thanks for all the help.

[Uptown Audio]

Wow. That could have been much worse. I'd still test the output tubes. Maybe you got lucky and it only behaved as a shorted tube and the fuse took the brunt of it. It could have also caused the tubes to behave as if they were shorted at the same time. You will need a new set of output tubes at some point anyway, I'd just go ahead and buy a set. That way, when one does crap out, you won't be without any tunes until you can find them. I guess you have a couple of spare fuses too (one main and one B+)?. Once you get a good set of tubes, you won't be blowing fuses in the Rogue though, that is if all else is well. They are stable enough without taking into account output tube quality.

Being cathode biased is not the same as being fixed bias, BTW.
-Bill 

[richidoo]

Being cathode biased is not the same as being fixed bias, BTW.

You're right, thanks.

Glad you found the problem usp!

[usp1]

Yes. I will now start looking for spare tubes. I have a collection of the 12au7 tubes which came with the amp. I need to get some 12ax7 and some kt88/6550 output tubes.

Incidentally, while i was looking at the circuit board I noticed some small oily deposits near one of the blue capacitors...I wonder if that is a leak and if so what effect it will have. Also is this something I can replace?

[srb]

Closer inspection showed a tiny screw that was shorting two component leads.

Incidentally, while i was looking at the circuit board I noticed some small oily deposits near one of the blue capacitors

Just goes to show, like CSI forensic technicians or Detective Monk, a careful unrushed visual inspection can often reveal a lot.
 
Steve

[timind]

Yes. I will now start looking for spare tubes. I have a collection of the 12au7 tubes which came with the amp. I need to get some 12ax7 and some kt88/6550 output tubes.

Incidentally, while i was looking at the circuit board I noticed some small oily deposits near one of the blue capacitors...I wonder if that is a leak and if so what effect it will have. Also is this something I can replace?

A leaking cap can be corrosive/hazardous to the board, runs, and surrounding components. If the cap is leaking you should replace it and while it is removed thoroughly clean the oily substance off. That is if the cap is leaking. Sometimes what looks like a mess is product used for vibration control.

[Uptown Audio]

Yes. I will now start looking for spare tubes. I have a collection of the 12au7 tubes which came with the amp. I need to get some 12ax7 and some kt88/6550 output tubes.

Incidentally, while i was looking at the circuit board I noticed some small oily deposits near one of the blue capacitors...I wonder if that is a leak and if so what effect it will have. Also is this something I can replace?

Probably not. It's likely either flux or something foreign spilled, splashed near the amp. Just wipe it off. Again, don't touch the circuit board, use a wooden or plastic insulator to hold the tissue when you wipe it off. The less you do at this point, the better off you'll be. If it's working fine, button it up and leave it alone...

PS: Never operate the amp without speakers attached.
-Bill 

[usp1]

PS: Never operate the amp without speakers attached.
-Bill

Now you tell me! I will be careful next time.