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One technical reason I don't like adjustable bias in Marks is because it allows people to adjust the bias too hot which can result in damage to the bias circuit in addition to leading to tube meltdown. I've found that modern manufactured power tubes are just more likely to develop grid shorts...

My recommendation is to leave those STR 416s right where they are if there's no compelling REASON to replace them. Based on their appearance and the getter silvering they're relatively fresh and have tons of life and many years left. Those are some of the longest lasting, most reliable tubes...

If you think a Mark III is hard to work on, I'm confident you've never worked as an electronic technician in most fields of electronics in the past several decades. By comparison with MANY devices I've had to repair, it's incredibly easy to do ANYTHING to any Mark series amp. If guitar amp...

I'm looking for a Mesa original reverb/eq footswitch for my Mark III. Not an aftermarket replica. That's all. PM me if you've got one available.

No, the amps didn't exceed the tube max specs, IF you were using the RECOMMENDED tube types. If you can FIND the elusive PhilipS/ECG/Sylvania datasheets for the 7581A, 7027A, STR387, STR415, or 6L6GC tubes, you'll find that the amps made for them may push close to the max ratings but won't...

No worries. I'm an experienced amp tech and quite well equipped, with tube testers and everything needed to service, troubleshoot, and repair just about anything that uses electricity.

What's the voltage on the cathodes? Plate to cathode voltage is the starting point for calculating your tube dissipation and thus proper bias voltage. It's not necessary, and is in fact probably a bad idea, to install adjustable bias on a Mark III. Stick with Mesa output tubes and their...

My Blue Stripe DRG Mark III gets "close enough" for me for the IIC+ tone, and its aggression and harmonic richness outclasses even my Mark V in the Extreme mode. The Blue Stripe is simply the most brutal and FUN amp to play I've ever plugged a guitar into, without exception. Going back a...

I happen to be fortunate enough to have a few Sylvania 6CA7s (STR-416 if Mesa branded) that are still quite good, healthy tubes. IF I were to put them in my Mk V, with these tubes I should not NEED to use the Variac power mode. Correct? Because they can handle the voltage!

Once I thought, "Oh, those silverface Fenders will NEVER become collectible like the earlier Blackfaces!"....priced out a clean condition '70s silverface Deluxe Reverb lately? For the same fundamental reason, yes, expect Mark IIIs to start climbing in value. I'm already seeing it, a little...

That is specifically Sylvania 6CA7sSTR-416s in the outer two sockets. There are a few on ebay. I would strongly recommend getting them rather than attempting to substitute any newer replacement, if the prices are in the same range. The Sylvanias can handle the high voltages in that amp.

You made a Mark III sound like a Marshall. And, honestly, not the best Marshall I ever heard. I can't say I think you got your money's worth here. To me it sounds like the amp I'd lose interest in playing before long. Not a win. I'd much rather pick up a Marshall 2203 or 1959 and send...

NOS 5U4GB tubes are readily available. Get some GEs or RCAs and you'll enjoy very reliable amplifier operation. Just to name one source, Tube Depot has them in stock. GEs are under 40 bucks each. How good are they? Well, there are lots of old Fender amps from the 60s and 70s that are...

You used paypal friends and family. You poor fool. NEVER DO THAT!!! By using friends and family you lose ALL buyer protections and paypal won't give your money back even if you have PERFECT proof that you got scammed. And you violated paypal's policies by trying to dodge their fees. They...

Never. Ever. Ever. Ever. EVER, use PayPal Friends And Family option to send payment for anything you are buying, where you do not already have a FULLY trusted relationship with the other party!!!!! By doing so you lose ALL buyer protection that PayPal would give you if you had simply used the...

It was actually a tube. It checked fine on my tube tester but that doesn't cover all possible operating modes. Strange that it would hum in triode mode, and not pentode mode, but it did. So, the 10/45/90 front panel switch is only correct in its labelling if the tube is set to pentode mode...

Update: Did the tube pair swap check, narrowed it down to a pair of STR 447s. Put in a well matched pair of spares, the hum is still there. I guess I'm going to have to pull the chassis and check to see if any resistor values around those tube sockets (screen resistors) may be off value and...

I've noticed that my Mark V 90 has developed a bit of a hum in channel 3, only in 45 and 90 watt modes. And only when the rear panel triode/pentode switch for channel 3 is in triode mode. 10 watt mode has no hum, and no power mode hums in either channels 1 or 2. Neither does tube/diode...

My dad taught me the cowboy chords when I was still in elementary school. I actually became interested in learning the guitar beyond that point around the age of 20.

Serial number starts with MKV-0056XX whatever year that is. My MKV head starts with MKV-015XXX. I don't know that it matters. The amps are identical other than the cabinets, as far as I can tell. They sound pretty much the same and work the same. As I understand it, the MKV serial...