[sdiy] Paia MIDI2cv8: building and modding

[John Blacet]

Hello All:

Just got through with the Paia MID-CV kit as part of an evaluation of
modular converters (also in house: the Doepfer A-190).

The kit went together OK and works fine. Using a stable (MOTM) VCO and a
digital keyboard for reference, the tracking was impressive  (8 bit D/A
converter). I was less impressed with the hole spacing for the
capacitors; virtually all of them were too wide for the supplied caps.

The manual mentions needing 300mA for +power, but I measured only +45mA.
This is because of the use of a "C" model uP for the 8031. This is good
news!

I decided to power the unit off the standard +/-15V Blacet power supply,
soldering in the wires on the supplied locations on the rear of the
board and using one of the supplied cable ties for strain relief. The
schematic is misleading regarding the location of two low value
resistors on the V+ and V- inputs, resulting in less than 15V on the
ICs. I pullled R51 and R52, replacing them with jumpers.

The MIDI activity LED was pretty hard to see so I replaced it with a
clear high brightness type.

Whenever you change the DIP switch settings, you have to power down the
module and power up to "read" the new info into the uP. Since I was not
going to use the front panel power switch for power, I connected it to
the reset line on the uP via a 1K resistor. The other lug of the switch
goes to VCC (+5V). You can pick up the uP reset pin at R6 and VCC at
R54, both on the side of the resistor facing the front panel. The front
panel reads "System Reset" below the switch, so wire the switch so that
when the bat is down, you are in reset mode.

The one thing I did not like about the DIP switch was the fact that it
was back from the edge of the board quite aways, thus back from the hole
in the front panel. You are going to have to use a small screwdriver to
change the settings in any case, so perhaps this is not a huge issue.

I still have a blank hole where the "Power" LED is supposed to go; I'll
leave it blank or add an LED later.

More info on this and the A-190 later if I get a chance. At first
glance, these units are quite different.

Regards,
___________________
John Blacet
Blacet Research
http://www.blacet.com