Fender Roc Pro700 help

xtremehardy388

I love my Roc Pro but I'm having a bit of trouble. The clean channel volume has virtually plateaued after the passing "2"...I have no idea why. Possibly dirty pots? Also, the drive channel seems extremely weak, suddenly. Any possible reasons for this? Am I able to fix this? I really do NOT want another amp as I absolutely LOVE this one (and am a bit attached to it).

Pacomc79

You could try cleaning the pots with some Deoxit. (might as well do this, it's the least expensive temporary solution and won't hurt anything)

Not sure if the preamp in the rocpro's has a tube in there I can't remember, if it does, it's a 12AX7 and you can swap it out that should fix the drive problem.

If not, it's probably a failing component. If that's the case, you just need to find a local tech willing to work on SS amps that can go through it and fix it. Sometimes it's simple. (I had a broken solder joint on a component in a Fender years ago fixed without much fuss for less than 100 bucks)

Go ahead and clean the pots first, maybe unplug it open the chassis and see if you can see anything obviously fried or broken. Lots of times it's just dust.

Pacomc79

Just looked up the manual.

I almost guarantee you the preamp tube in that thing is going bad.

check out http://www.tubedepot.com and http://www.thetubestore.com

pick your favorite new production 12AX7A and go ahead and clean those pots.

xtremehardy388

Thanks Paco! Haven't seen ya in a while (I've been ghost for a bit). Hope all is well



How do I clean pots? I'm pretty new at this


Also, can I use a 6L6 tube??

How do I change tubes? How dangerous is it?

Pacomc79

Hey man, me too.

You need to find you a good contact cleaner like Caig Deoxit. Generally you can clean them by gently spraying around the shaft of the pot (very lightly no need to soak it) and then turning the pot to work in the cleaner. I like to open the thing up and spray inside the body of the pot a bit, but that's just me. It's best to try not to soak the circuit boards or anything. You can use a comprssed gas duster to remove some dust, but like with computer equipment you need to be careful not to coat the board with the propellant.

NO you cannot use a 6L6. for one, it's a power tube and not a preamp tube (at least in the general sense, I've never heard a 6L6 being used in a preamp not saying it's impossible I don't know) That said it won't even fit in the socket in your amp it's way too big.

It's not hard at all to change a tube, (think lightbulb, but with pins instead of a screw in base) I like to spray the sockets with a little Deoxit again when I change tubes, but that's just me. The main thing is just making sure you get it seated into the tube socket correctly and deep enough.

It's not dangerous, just unplug and wait until everything is cool (again lightbulb analogy)

Changing a preamp tube is not like changing power tubes where you would have to rebias (on a non fixed bias amp) The power stages of amps are sensitive to how hot or cool the tubes run so it is important to rebias when you swap out power tubes but not in this case.

The tube you need is widely available for under 20 dollars. in fact there is a sino 12AX7A available for around 9 dollars. (I think you only need one)

12AX7A's are what you are supposed to have in there so if you want a direct swap the sino is probably a good option. I believe it is a chinese tube, but they are popular in marshalls and bogners and the roc pro is high gain as well.

here's another option for a chinese 12AX7A this one is from shuguang. http://thetubestore.com/chinese12ax7.html

I think the sovtek 12AX7WA would do you right as well in that application.

You can look up the manual on line if you want. Good Luck!

xtremehardy388

I have an extra 12AX7! Thank you SO much for your help. I will let you know how it goes, this weekend!

xtremehardy388

How can I tell if the tube is bad or going bad? What should i look for?

Pacomc79

read your first post. The amp sounds like it's dying. Sometimes it will sound just not right, like it's mushy, sometimes it will cut in and out. Sometimes it won't make any sound (and the fuse is fine)

Did you try the new tube yet?

mccreadyisgod

I remember the tube in my Roc Pro 1000 head was a pain in the ass to get to... buried in the chassis, which had to be completely removed from the cabinet so I could get inside. A proper tube amp has tubes accessible right on the outside, but they made it tough as nails to get to that drive tube.

Reading the original post, it seems like the problem is either not the tube, or not just the tube. The 12AX7 in this amp is exclusively for the drive channel, so if you have a problem in the clean channel, the tube is not related to that. It almost sounds like a slowly-dying power transformer... really weird.

If I understand the conditions correctly, your clean channel won't get any louder past "2", it just hits a max volume and stays there? Does the signal get distorted in any way, or change tonally, past 2? Or does it not make any difference if the knob is at 2 versus 9? That could be a problem in the potentiometer, for sure. Or it could be a problem with the amp getting enough juice.

Regarding the drive channel, you say it seems "weak." Is that weak input or output? Rather, does the overdrive seem less, but the volume is plenty, or is there a problem with output volume? If you have a problem with output volume, is it similar to the problem in the clean channel? Have you experimented with these problems both with and without the amp's footswitch? I remember my Roc Pro having some sort of problem that seemed to be related to the footswitch, but it's been years since I played that thing. I do remember that the amp uses some weird type of channel switching mechanism, since the footswitch connects via a 2-conductor cable, but switches three different parameters (Drive, More Drive, and Reverb).

To answer your last question, Paco is right... a dying tube (especially a preamp tube) can exhibit a lot of different symptoms. It's entirely possible that your preamp tube is on it's last legs, especially if you've had the amp a long time and never changed it. But the problem in the clean channel makes me almost certain that the tube isn't the culprit (or the only culprit). It could be that a dying preamp tube took down another component that is now causing the problem in the clean channel, but the tube isn't directly in the signal path of the clean channel. Paco's info is right on regarding the tube info, so I have nothing to add. G/L.

xtremehardy388

Update:

Clean channel seems to be working---just a dirty pot. The volume stayed the same after 2 but now it seems to be fine.

The drive channel is back to normal. I don't know if I should change the tube or not. Things have been hectic around my area---getting ready to propose to the GF, tomorrow.

I realized that after changing a cord from the amp to my first pedal (Ibanez FL9) the problem was remedied.