Recent content by Restless Rocks

You have a leaking capacitor in the tone stack. Replacing the pots will not help.

As you can see in the schematic, the ground switch is what we call an "on/off/on" type. In other words in the middle position the cap is not connected to either the hot or neutral ac line. Same as being removed.

Yes. It was the single EVM 15B loaded bass cab, tuned to the "Thiele Small" parameters just like the 12" version for guitar. Looks just like the 12" "Thiele" cab but a bit larger. There was a RoadReady and a Tolex covered version. You see one on ebay every now and then. You can find a...

Sounds like you have a loss of bias voltage to the output stage, either from a shorted tube or damage to the circuit from a previous shorted tube. Take it to an authorized Mesa Repair Tech.

What does it do when you turn it? If it is the Rhythm II master volume, it will only operate when the amp is in the RII mode and all it does is allow you to balance the RII volume with your clean and lead settings. If it were a factory done mod the RII control would have been placed in an...

I've seen this done to a MkIII a couple times, but never a IV. Many III's have a hum issue, which I've connected to certain brands of tubes and especially vintage long plates in the VI and II spots. The solder looks well done but I don't recall a mesa bulletin on it. I'd guess a custom job.

Just some freindly advise; be sure you put your EL34's in the OUTER sockets only. I just finished an extensive repair on a MkIV where the owner mistakenly thought he could use EL34 in all sockets. That is a big no-no!!!. This caused arching and burning of the circuit board and even the...

Actually it is not a difficult job to add the reverb circuit to a non reverb Mark amp. All the chassis holes are already there and it is possible to install the additional tube socket without a full circuit board lift. I've been able to raise it about half an inch off the standoffs and slide...

This depends entirely on which stripe mkIII you have. The published schematic is the original nostripe/blackdot design. The circuit board was changed in the purple stripe and each stripe after has it's own particular R2 version.

Everyone seems to have reliability issues with the 6BQ5/EL84 tubes. What are you using that has best life and tone?

I'm just finishing restoration of a Mark IIb short head and the original reverb pan is already mounted with the output side opposite the pwr trans. Mesa also had the forsight to put those metal plates over the open side of the pan. This one actually has a second 4"x4" metal plate over the...

Sounds like the frame is warped from a drop, this puts the voicecoil out of alignment. I've heard of a couple speaker repair shops claiming to be able to fix (Miller Sound Pennsylvania) this but it is very difficult to ever get the magnet lined back up.

Ditto on replacing the push/pull pot. But have the tech do it. He could also tell right away if the switch is opening and closing as it should anyway.

What Stripe is your MkIII? What tubes are you using? What speaker/s are you using?

In the last couple years It's become alarming at how many BRAND NEW name brand tubes I've installed that failed either immediatly or within a few hours of being powered up. It makes one think that they are not tested at all under operating voltages. Please be patient with Mesa and staff. They...