Derek Revell's Website
"The Phutney Prototype "
Built up the PCB's
Serial No. P0001
Sold to Jonathan E.
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MkII X board - Only populated with Power Supply components - highly recommended, if you don't want to fry the MFC6070 and 741 I.C.'s
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MkII X board - Fully populated, debugged and calibrated and 100% working without any trace errors.
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I'm sorry I seem to have misled people, I never said I was going to offer kits or fully built modules, the truth of the matter is that this project has required all of my skills to complete, I have been in Engineering for 42 years, and my hobby was electronics before I started my craft engineering apprenticeship in 1968, you will need a great deal of DIY skills to build a clone for yourself, even if you have the necessary components.
You may have downloaded a set of circuit diagrams or schematics for a Synthi A or VCS3, but don't automatically assume those are correct and without errors, they are most definitely are not, I have done a comparison with my Synthi A and have redrawn them. It is these drawings I have used to construct the Phutney PCB's.
I have made the clone , using the dimensions of the original synth they are H 44cm x W 43cm x D 42cm.
The panels sizes are upper W 40cm x H 32cm x 2mm and the lower panel is W 40cm H 30cm x 2mm.
The Phutney clone wiring is complete on 16/03/2010, and now is fully calibrated.
I have finished the track layouts of the three main PCB's.
I have finished wiring up Board X's connections to the Patch Panel and I/O, and have tested my original Synthi A board in that position, I was a little bit nervous as I powered up, but all was well, and I measured the +12V and -9V d.c. supply, and confirmed that they checked out to within tolerance. Board Y connector is completely wired up, I tested both boards X & Y, I had a problem with the reverb circuit, but soon realised where I had gone wrong, and corrected the error, finished the wiring to Board Z, tested all the boards, but had issues on all three Oscillators, but with calibration and using my fault finding skills managed to sort them all out.
As you can see I have used plastic conduit to guide the wires, as I don't have wire mans skills, and I didn't want the wires to look untidy, so I have just run them in the conduit, when I have finished, I'll put the top covers on, and should I need to add any further wires, the process will be very easily accomplished.
I have adopted to use a Ghielmetti Type 621, 20 x 20 patch bay, this is because a 16 x 16 matrix is classed as a "custom" patch bay and cost double the price of a standard 20 x 20, but changing the 20 x 20 to a 16 x 16 is a relatively easy task, but I chose to use the 20 x 20, as I plan to add some extra features, which were planned on the original, like voltage control of oscillator wave shape, and filter response, but as the 16 x 16 matrix were cheap and available, the additional features were shelved.
I didn't like the white finish of the Ghielmetti Matrix Panel. so I ordered a piece of Black poly carbonate and re-manufactured the top panel.
Finishing the wiring, tested all the functions, only a few issues, incorrect wiring to the joystick and Osc 2. now to the manufacture of the 3 PCB's.
I got the PCB's made, the guy quoted me £120, but they actually cost £212, that was for the three prototypes.
I've now populated all boards, and after correcting about 10 track errors per board, I managed to get all the boards working. The biggest problem I had was with the setting up of the Env. Shaper, in contrast the Filter just burst into life, as did most everything else, I had an issue with the Reverberation circuit, any signal passed through became distorted, I found that I'd missed a connexion between ZD3 and R312.
I also found that the setting up of Oscillator 2 and 3 wave shaping, is very time consuming, mainly due to the bad design of the original circuit, it would have been easier to put some presets in there.
I also have worked out how to modify the 24dB/Octave filter, to 30dB/Octave, although people who have a better knowledge than myself, argue that all EMS Filters were 24dB, it was fear of getting litigated by Moog that EMS decided to call the Filter 18dB/Octave, and so the clever subterfuge worked.
I did a deal with Harry R, and he made me and himself another set of boards these were Mk2, and so I've populated X, Y and Z boards, I had issues again with the wave shaping on Osc2. Harry pointed me in the right direction, I'd missed a couple of connections. With those corrected and with the circuit working correctly, I managed to set up the wave shaping on Osc 2 and 3, with no issues.
I found the reason for the amplitude variation on Channel 1 & 2 which was occuring when the envelope shaper was recycling, the audio signal wasn't even going through the envelope, yet the VCA was being modulated, this turned out to be that the 20mA filament lamp was causing a high current draw that was effecting the VCA output amplifiers on Ch.1 and Ch.2, I got some low current 12mA LED's and put one in series with a 8V2 Zener and a 1K resistor, job done.
I understand that people who lust after an original, are not prepared to compromise and buy a copy, and clone builders haven't got the necessary finances to make a big single investment, but would rather spend small amounts over a longer period to achieve their own instrument. it was this reason that prompted me to offer just PCB's to amateur Synth builders.
I've also built a Test Rig for board X, out of some scrap wood and spare aluminium off-cuts I had laying about in my shed, see pictures on this page, these were taken before I'd finished all the wiring.