QTron Work

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Moraz Mark V
QTron Work
Reveals - Almost
Mark V Reveal
QTron Reveal
QTron Departure
Ranch and Health Spa


#210 - partially disassembled

It didn't play.  All the magic blue smoke came out of one of the amps.  There were wires hanging all over the insides in the vain attempt to quiet the noise.  Some tapes were broken.  Some tape separators were broken.  It didn't cycle.

But it was all there.  Mark II #210, the "QTron", is a wonderful Mike Pinder machine left in nearly original condition.  Unlike Mike's other machines, this one still had the original power supply, amps, and even one speaker.  The original preamp remained as well.  The thinking is that this machine was used for recording and never toured (or toured lightly).  Cosmetically this machine wasn't too bad, aside from some nicks in the veneer near the bottom and a few marks here and there along the edges.

As with any Mark II, Jerry had his work cut out for him.

Mark I or Mark II restoration begins with the renting of an engine hoist.  Seriously.  Click on the image to the left to see Jerry Korb with a Genie Lift removing the innards from the Mark II.

After the main frame is removed from its case, it is set into a stand purpose built to hold the various Mellotron models (and a table top later on when there are no Mellotrons being worked on).  With the QTron the owner wanted new tapes, so the old tapes were wrapped up for safe storage.

Yep, one tape was replaced who knows when, accounting for the difference in color.

I've Been Framed!

One of the things that has come to light in recent years are the vulnerabilities in Mellotron frames.  We all know the Sound Sales bodges that put M400s in peril.  The Mark II has an inherent design flaw that can lead to cycling and motor problems.

The frame is made more stable by replacing the wood side boards with new, thicker ones made of better material.  You can see the side boards in the picture with the Mark II hoisted up on the Genie Lift.  Doing this was a boon to Jimmy Moore's FX Console, and it's something Jerry does to all Mark II series machines that he gets in.


Getting Ahead...

As we found out when the first Pindertron was being worked on, these Mark IIs sometimes aren't as quiet as they could be.  One reason?  The tape heads are wired incorrectly on what may turn out to be most of them!



There are several modifications being researched to quiet down Mark IIs, this being the first of them.  Additional work has been done in the power supply and other areas with a lot of success.

And don't forget the pad arms!

If the bends in these things aren't right, they won't play right.  A few of these were questionable, huh?

If the frame sags, the adjustment becomes more difficult.  If you're adjusting your machine, and you have to crank the adjustment screws too far, there is something wrong.  I've seen adjustment screws buried in the keys.  There is no need for this.  This indicates your Mellotron may need some kind of repair, such as stabilizing a sagging frame.



Got a Mark II?  Then you probably have a collection of valves...or tubes.  Well, except for Frank Samagaio's Pindertron, which had its tube preamp removed.

<-- Look inside the preamp

The Mark II has a bunch of other electronic bits.  It's actually a rather complex piece of machinery considering everything that has to work right in order to get sound out of it.  The most complex subsystem is for cycling tapes.  It comprises cycling motors driven by the Station Select Control Unit (SSCU), a dial wiper for ballpark station location, and a tape with a 1 kHz pulse recorded on it to point out the station's exact location to the SSCU.  These days you'd do it with a stepper motor or a simple integrated circuit.  Back in 1963 you built an analog computer, which is what the SSCU is.  It's amazing they work at all--and many times they don't, so they have to be repaired or replaced.

Left hand SSCU.  Yes, it has two to worry about.

Left hand cycling motor.  There are two of those as well.

The Mark II, FX Console, and M300 have audio amps.  I thought these were going to be tube based as the preamps were.  Nope, they're solid state--transistors.  The blue smoke escaped from one of the QTron's two audio amps, so it needed to be repaired.

<-- Getting repaired

<-- Two happy amps

The Mark II foot pedal controls the machine's volume, but how it does it is...well...a nightmare.

As you press down the foot pedal, a wiper makes electrical contact with a series of wires with resistors on them.  The various resistors cause the volume to change.  Needless to say this is not very smooth, and this system introduces a lot of crackling.  Many times the foot pedal is bypassed, and in/out jacks are introduced on the front instead.  This allows the use of an external, high quality volume pedal.

Oh, right, nothing goes anywhere without the power pack.

This guy powers the whole machine.  #210's was re-capped (had its capacitors replaced---the old ones were ready to blow up) and had some low-noise modifications.

Another interesting piece of Mellotron electronics is the VFO--the Variable Frequency Oscillator--known to me and you as pitch control.

The VFO pictured with the audio amps.  And you wonder why these machines are so heavy?

The VFO in conjunction with the old CMC-4 motor controller card drives the motor that turns the flywheel and capstan.

And, finally, the Mark II has its own built in reverb...well, something that they call a reverb anyway...The Mark II reverb is nothing more than two BSR phonograph cartridges with tape return springs strung in between.

<-- Mark II reverb <-- Reverb driver

Needless to say that the reverb units are removed and replaced with far better reverb tanks.  Jerry opts for Accutronics reverb units custom made for the application.  Accutronics is only too happy to provide custom made tanks, including meeting the original Mellotron specification...except they don't suck.


Clearing the Path

Mark II #210 needed a bit of work done on the tape path.  Several of the tape separators were torn and some springs were hurting, so Streetly Electronics provided some replacements.

<-- Tape separators ready to go in.

Hmmm...One slight problem, though.  These new separators weren't exactly flat, and the tape path has to be pretty spot on in a Mellotron--especially a cycling Mellotron.  So to break in the new tape separators, Jerry installed them and put weight on them to get them to settle in.

<-- Tape separators go to the gym!


Additional Body Work

#210 was in really good cosmetic condition for its age, but Jerry did a little bit of spiffitizing anyway.

<-- Those chips in the veneer along the side--fixed

#210 also received a brand new hatch cover to help keep dust--and curious fingers--out of the machine.


Whew, a lot of work.  Have a beer, Jerry.


OK, let's move on to The Reveals -->