Workin', Unbodgin'

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Workin', Unbodgin'
Fire Hazard!
#541 Unveiled
New Home


Grand Funk's 'tron, now owned by Stewart Myers, is in for repair

<-- Stewart's machines in various states of repair (as of this MONEYPIT most of the work was done, and Jerry was waiting for warmer weather so the refinishing work could begin)

See the unveiling of Stewart's machines in the next MONEYPIT adventure!


Unlike two of the four M400s in Jerry's repair depot these days, Lee's #541 was never bodged by Sound Sales.  As a review, here's what a Sound Sales bodge is:

bulletTake a working M400 and wreck it.

Whew--one of the lucky ones that escaped Sound Sales!

And how they did it:

bulletMove brackets from the tape take-up box from the bottom of the box to the top.  This weakened the M400's internal frame and often resulted in tapes that were too high or too low when running over the tape heads and capstan and entering the take-up box.
<-- Click for a bigger image.  Note the results of the weakened frame over time when you add the weight of the flywheel and the motor belt tension.  Eventually the machine becomes harder to adjust.
<-- Lack of support under the take-up box--the whole assembly now sways
<-- The bracket is an OK idea to replace the wood wedges there originally, but it's around the wrong way (the front-back slots should be on the box, the up-down on the frame) and there's no corresponding support on the frame sideboards under the take-up box, leading to the swaying and bending of the frame
bulletImprove the sound on each tape head.  This was done by bending/warping the pressure pad arms when all that was needed was an adjustment using the slotted screw that holds each pad arm in place.
bulletSquash two pinch rollers between the keyboard and the headblock for improved stability during travel.  Not really needed.  Made track selection harder.
bulletRemove the stabilizing blocks on the side of the case near the motor.  Maybe they figured their other "improvements" meant that motor support was no longer necessary?
bulletPut a big sticker on the power supply proving the fine work that was done.  (Does nothing but lower the value of the machine.)
bulletCharge the customer several hundred dollars.  And for that privilege the customer receives his machine back in worse shape than before.  (This was the fate of Larry Fast's M400---a machine he never used again, thus changing music history.)


One way to tell a bodged machine or at least a machine that's got some issues is to look at the depth of the pad arm and pinch roller adjustment screws.  Notice on this one the screws closer to the flywheel are down more, some buried in the wood.  This would be a symptom of the frame starting to sag.

(Now why is there "805" on that keyboard?  I have no idea!  #805 is scratching his head, too...he has the original #805 keyboard!)


The one thing Sound Sales did right:

bulletReplace the CMC-10 motor controller with an SMS-3.  But because other things were messed with, the improvement wasn't obvious.
<-- SMS-3



Lee's machine?  Fairly straightforward, no bodging.  It just needed a tune-up to get it playing right.

Disassembly of #541

<-- Initial inspection/cleanup of the electronics.  Yep, the CMC-10 has to go!

Tidying up the keyboard:

Hanging out your Mellotron laundry?

Those are the springs from Lee's tape frame after being cleaned up...drying on a clothesline.  Go light on the starch, Jerry!

Actually this is a cunning plan to locate the stretched and knackered springs.  What the heck, let gravity do the work!

And what's a new tape frame without a new set of tapes?

As you can hear from "Leaving for the Black Sand", Lee opted for:

  1. Ian McD Flute
  2. String Section
  3. Combined Choir

Now with the SMS-2 in-hand, it was time to modify the power pack, swap in the new pitch control, fire up the motor, and look for 22 volts:

OK, 22.03 volts.  I guess that's OK.  :-)

Typical Korb Mods

These are typical JK mods to Mellotrons that go through his shop.

  1. Take-up box cover.  Jerry fabricated these; they are available from him if you need one.

  2. Orient the take-up box brackets correctly (and make sure there is a set of brackets on the bottom of the take-up box!); optionally replace the original wedges at the top with a bracket if desired.  Brackets have been fabricated and are available.

  3. This is a new one.  Several people have complained about noise when changing the track selector or a rustling noise or hiss on one track but not others.  In consultation with John Bradley of Streetly, a modification has been developed:

    A small insulating piece of plastic isolates the bolt holding the pin of the track selector.  Note that there is a sleeve in the bolt hole as well to keep the pin isolated from the track selector arm.  The idea is to electrically isolate the track selector pin from the arm.

  4. Avoidance of "Screeching Cable Rot".  By now your M400's audio wiring is dust.  When it fails, you will hear a screech in your headphones, and you may magnetize your heads.  The audio cable between the headblock and preamp is replaced.  Optionally, the cable from the power pack to the volume jack and output jack can be replaced as well (and probably should be by now).

  5. The power supply is fixed up cosmetically but more importantly the mains is rewired to avoid a potential fire/shock hazard.

With the work done, this guy is about ready to be unveiled!  But first there's something you really need to know about your M400.  Yes--and this is unfortunately quite true--your little white beastie with black feets is a fire hazard.-->