Iv'e got a Matchless chief that is fluttering when i turn volume up

[likelarry901]

Has anyone had this problem and is it serious?

[cyclone]

Been there, look at solder joints.

Has anyone had this problem and is it serious?

YES, I had that exact problem in a '94 SC120 that I still own. It was a mofo to diagnose, but what I saw was spikes on the scope at 1/2 to full volume. They got more pronounced the higher the volume went. THis is with a 1khz sine wave into a 4x10 Marshall cabinet with 35 watters. It didn't happen when plugged into a dummy load and I like little speakers with that head. Marshall took it Our practice place was a former meatpacking plant storage room with cork on the walls and a foul smell. my cabs and guitar cases still stink like that place, takes me back...

ANYway, the amp would disappear next to the band, but looked OK statically, current and voltage wise, 540 volts on the plates and 46 ma on each crappy eastern bloc EL34 in class A territory. It sounded fine at low volume and did not exhibit the problem into a dummy load as observed on the scope, but when I scoped it going into the cabinet while playing it, I could see the breakup as I increased the output. I tried swapping all tubes, etc. I finally took the head out of the cab one night and inspected every solder joint. I found that one of the grid wires on the phase inverter tube was not soldered. It was wrapped and crimped but had not been flowed with solder. At high volume the connection vibrated and effectively removed the drive signal from two of the output tubes. I touched the iron to it and it was fixed. Twice as loud and it sings. I know I've posted about this before on the innernet but it was a few years back.

There are a LOT of wraps and solder joints in a Matchless by nature of their construction. There are no tag boards or printed circuits, only tag strips. The preamp is wired using component leads directly to pots and tube socket terminals in a spiderweb. There is clear heat shrink on each lead to prevent shorts, but the conductors are the component leads. There is very little wire inside the amp, with the exceptions being the AC wiring for heaters and the "dash lights" I think this is a good thing because everything is so random, not laid out in nice capacitively coupling rows. May be one of their rediscovered "secrets" of preamp layout.

Check (or have a competent bench tech check) all solder joints in the amp. This amp has highly lethal voltages in it and no cover over the filter caps, and no multicaps. The filters are axial caps, inside and exposed, soldered to tag strips and you can fry yourself or the amp easily if you are careless, even if unplugged. They must be discharged safely.

This amp has an amazing sparkle and so much power. People say it doesn't have a lot of breakup, I have been using the Sovtek EL34's for a couple years, they break up really nicely in this high voltage amp, and don't short!! I like the master volume and the tone controls only shape the sound, particularly the mids and presence. I'm collecting NOS sylvania 6ca7's to try in it, I have two so far. I don't play much anymore and the Sovteks have sounded really good in this thing and aren't letting up. I don't know about currently available tubes, I'd probably go with what Matchless recommends as they still build this amp. Very high voltage and current requirements on this amp, no Siemens or Mullards will hold up.

I am currently building a mini version of that amp, using 4xEL84s in class AB with 30 watt TDS (matchless) xformers for my son, he doesn't need a 75 pound head but loves the tone. I have taken a lot of pics of the inside and created a schematic of the audio section (no power supply yet) I'll be digging into this amp more soon and I will post any drawings or pics that I come up with for anyone interested. I own gobs of amps but this one is by far my favorite.