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PAiA 9308 FatMan Rackmount Midi Analog Synth #2
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PAiA FatMan 1u Rackmount #2!!


PAiA FatMan 1u rackmount #2

Well... This 2nd FatMan came to me around the time I finished the 1st FatMan. It was up for grabs on eBay, fully assembled, complete with BLUE Front Panel, but noted "NOT WORKING PROPERLY".
Since it was offered at a quite cheap price, and I had just finished the 1st FatMan, I thought I'd grab it and fix it and do a 2nd FatMan Rack, maybe with additional Mods...

So it came to me like this...

In fact it was kinda dusty and seemed old - although the Front Panel was kinda pretty new, no scratch or anything (but again dusty). The PCB was dusty/dirty, and it actually has an older v1.8 PROM.

I didn't bother to really test it out, it powered up, made a sound, and i thought it was OK... so i cut off the hanging wall wart power adapter, and it sat on my shelf for a few months...
Finally got time to sort this 2nd FatMan out... Again it'll go into a 1u plastic ABS rackmount case. So knowing that i'd have to re-wire all the pots and so on, i decided to remove the front panel, cutting and removing all the original wires....

The BLUE Front Panel, as opposed to the BLACK one that came with the later FatMan that i ordered last year.
However, i realized there are some minor problems...
bulletNo wonder it wasn't fully working - the soldering on the PCB was real bad - i mean bad - I haven't seen any soldering worst than my own (!), and this PCB must be really badly done... Big blobs of solder everywhere, components not seated perfectly etc.... + some PCB tracks looked as if they've been cut or damaged. Checked these and they're ok tho.
bulletWhen i did the 1st FatMan rack, and when i wrote up these pages, I didn't put down any instructions for the mods I did, since the info's are readily available on other websites...
bulletBUT, when doing the 2nd FatMan, I found that I had to go thru all the websites and notes I put down, to summarized again and pick what mods I wanna add...
bulletThis has v1.8 firmware PROM... it has some issues with MIDI Velocity....
In the end, halfway though doing this, I kinda gave up.
I have left some space for further mods if i want to add anything in the future, but since this 2nd FatMan wasn't constructed by myself, I kinda loose interest in making it better.
It's kinda working, but a bit dodgy, but still usable...
UPDATE: After changing the power transformer to a higher rating one, it seems to work fine.
Anyhow, in case I do a 3rd one, I'll put up all the stuff in clear instructions/directions on these pages.

The FatMan 1u Rackmount #2

Originally I planned to have more mods, but at the moment, just all the basic mods.
Notes: Most of these mods are from Scott R. Gravenhorst's excellent Synthaholic's Fatman Site.
- Lee Diodes Replace R38/R39 with LEDs + add 100uF caps to C28 and C29
- 555 -> 7555 Replace 555 IC's with 7555's
- VCO Pitch Extend Change R35 (1k resistor) to a 680R
On FatMan Rack#1, I added a Switch to bypass R35, but this time I feel I don't wanna spend lots of time tuning this thing - so i just reduced the 1k resistor.
- VCO Fine Tune Additional 5k Pot in series with the Pitch Offset
- New Hard Sync (Switch) VCO1 (Pin4) reset by VCO2 (Pin3) - I cut the PCB trace at VCO1 Pin4 to add the switch.
- VCF BP/LP Select (Switch) Extra wire out of the Filter IC to a switch
- Extended VCF Freq (Switch) Switch to short resistor R73
- Max Resonance (Switch) Switch to short resistor R114
-> See the MODS Page for details

Left loads of space in the middle, for future expansion, like individual VCO level pots etc....

On the Left:

- Mains Power Switch, Midi LED, Main Volume
- VCO Pitch, Fine Tune, Sync Switch, Glide, Offset and 1/2 Mix
- A(S)R, A(S)R/AR Switch, Attack, Decay

To make the square-ish hole for these illuminating Power Switch, another one of these Hand Hole Cutter is needed. This one is the M10 rectangular hole cutter,22x19.6mm, RS Code: 600-161.
The Power Switch is one of those DPST green (or red) illuminated rocker switch, 10A/4A.
RS Codes are Green: 318-070, Red: 318-064
On the Right:

On the right:
- VCF Velocity, VCF Pitch, LP/BP Switch
- Frequency Extend Switch, Freq Pot, Resonance Max Switch and Res Pot
- VCA ADSR, VCA Velocity, Gate LED, Punch Switch and the A/D/S/R Pots.


The Audio Out on the LEFT, I did put a socket for Audio In, but i didn't bother wiring it up, as I probably won't use the Audio In on this FatMan#2...

The CV Outs, Midi Thru, Midi In, Fuse and IEC Main Socket on the right, pretty much the same as FatMan #1...
To make the IEC Mains Inlet hole, I use a screwing hand tool, which is an M10 Radius Hand Hole Cutter, 28x21mm (
RS Cat.#543-614 or or 541-501), with matching 10A Snap In PCB Mount IEC 320 Plug Socket (311-8031 or 488-191).


As of 11th July 2004



Some Comments on 2nd FatMan...

bulletBoard is old, soldering was not good... old v1.8 firmware PROM
bullet- Tuning not as stable as FatMan Rack#1
After changing the transformer to a higher power one, it seems that the problems i had were gone...
bulletSomehow I think the noise/hum level i get on this is greater than the 1st FatMan

But i suppose it could still be used a lot, there are many things that the FatMan can do, with the 2 detuning VCOs and also the AR/A(S)R VCF

bulletMay get a newer PROM (v1.9) from PAiA... then maybe i'll add more mods...
bulletIf you wanna get a FatMan, get the kit and build one yourself. Unless you wanna buy one completely built and fully working (like the ones that i think some Japanese Music Shop in Tokyo sell). Otherwise, it is much better building one rather than checking other people's work for faults, it's even harder....





Well... I got a third one...


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