mini compact mod project

[joelindsey]

Copied this from my post on the yahoo group...

Looks like I'm going to be modifying my beater/parts mini compact. Several parts on the tab switching assembly are either missing or broken, so I figured instead of trying to hunt down overpriced replacement parts I would just build something else instead. Somebody back in 2002 posted some details of his modified mini with some sound clips on the Combo organ yahoo group, and it sounds amazing. I'll do something very similar to that. I'm usually against modifying vintage instruments such as this, however this is already a beater that I have taken the nice parts off and put on my other Mini. Ideally these modifications would be reversible, though it would require a great deal of rewiring to bring it back to stock.

Here's what I intend to do:

-replace the 8' buss with a mixture of 5 1/3' and 2 2/3'
this requires rewiring the entire 8' buss. To get a mixture of the 5 1/3' and 2 2/3' I put two 100k resistors between each divider, and that is where I will pull the mixture from and rout it to the 8' buss. This is the same way Farfisa did it with the FAST-4 and 5. Due to the oscillator/divider boards only having six octaves available, the mixture's top octave on the keyboard will only have 5 1/3'.

-Make each voice for each footage controlled by a pot, as well as vibrato depth and speed, like the one posted in the files section. This allows a great deal of flexibility.

-Voices I hope to include are flute, trumpet, and string for each footage. The original flute filters will probably be used. Trumpet and string will need to be built from scratch. Unsure of whether to use op-amps or transistors. Whatever is easier. I may just copy some filter designs from the Combo Compact or other
organs.

-Ideally everything will be mounted on a new face plate that will go where the old switch board was.

Just figured I'd post it here in case anybody is interested. Feedback is welcome. I'll be uploading photos of the process on Flickr as I go. Currently the mini is on the bench with the shell and keys removed. Looking forward to digging into it!

[joelindsey]

Here's an update on my progress so far:

I'm keeping some 8' in the mixture, so it is a 8', 5 1/3' and 2 2/3' mixture buss.

Adding the 100k resistors for the 5 1/3 and 2 2/3 mixture on the tone generator boards. I would have liked to add these on the keyswitch board so I wouldn't have to run an extra 48 wires total from the TG cards, but there will already be a mess of wires there so it's a trade off.


Here's the wiring for the top octave of the mixture. Because the TG cards do not extend beyond 4', the top eight notes of the mixture buss can only have the 5 1/3'. To compensate for this and fill out the "dead space" in the high end I added in some 100k jumpers from the 4' buss, thus adding in some 4' to the top eight notes.

[joelindsey]

Here's a few more photos of the wiring. I'll be glad when this is done and I can move on to the filter and panel design. I have about an octave and a half left to finish.

This is a real mess. The green wires and blue/grey wires are the mixtures pulled from the generators.


Here is what it looks like up close. The small blue resistor is for the 8', the wire behind it is the corresponding mixture.