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Help needed JL Cooper cv-midi
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Help needed JL Cooper cv-midi
bmot
Can anyone give me a hand getting this working? It’s a NOS „mini-midi cv in“ that I picked up at Vemia. I connected a 9v battery and it immediately gets very warm. I guess this is a bad sign, right? The soldering looks incredibly old, should I try redoing it (I’m not a great solderer but I can try).

The power input is unlike anything I’ve got, very narrow barrel, even narrower than the ProCo Rat.

The bottom right of picture one, you can see two round black components that can be adjusted, I would guess this is important but there are no clues. Help!

Anything else you can tell me about it would be appreciated too. I am guessing, and hoping, it converts cv to midi, as that’s what I’d like to use it for.


StillNotWorking
Do you have +9V on tip of sleeve of the power connector?

Marking on the back of the PCB will have you connect positive to sleeve, but my first impression this pin aslo goes to sleeve on CV's which usually are ground. Try to trace out the earia around the voltage regulator an loock up datasheet for the regulator to make sure what pin should go to positive. It most likely are a 7805.
bmot
Sorry i don’t quite follow. What did was put crocodile clips on the + and - as shown on the Second Photo, and connected to a 9v battery. That should work right?
JohnLRice
I found this: http://search.retrosynth.com/ah/search/lookit.cgi?-v9812.1937

**************************************************

Reference info for the JL Cooper single channel MIDI - CV converter,
for anyone who needs it.


Front panel switch allows choice of what happens when more than one note
is received.
High Note - highest of the current "ON" notes is converted to CV.
Low Note - lowest of the current "ON" notes is converted to CV.
Last Note - each new "NOTE ON" command becomes converted to CV out,
replacing the previous one.

Internal switch to select whether a GATE ON condition is taken as a high
voltage (most systems) or a low voltage (Moog S-trig)
Set switch 5 to OFF for MOOG S-trigs


Channel Number (internal DIP)
Each NOTE ON and NOTE OFF command received is checked to see if
its channel number agrees with the setting of the internal DIP switches.
Switches 1 thru 4 are set as follows:

Channel No. SW.1 SW.2 SW.3 Sw.4
---------------------------------------------------------------------- ------
--------
1 off off off
off
2 on off off
off
3 off on off
off
4 on on off
off
5 off off on
off
6 on off on
off
7 off on on
off
8 on on on
off
9 off off off
on
10 on off off
on
11 off on off
on
12 on on off
on
13 off off on
on
14 on off on
on
15 off on on
on
16 on on on
on


Internal trim pots are Offset (left) and Scale (right), looking
from the top of the circuit board, with the rear panel connectors
at the back (top).
**************************************************
StillNotWorking
bmot wrote:
Sorry i don’t quite follow. What did was put crocodile clips on the + and - as shown on the Second Photo, and connected to a 9v battery. That should work right?

I'm questioning if polarity marking are correct. Mostly course the power connector sleeve are marked as positive and this trace also goes to sleeve on CV connectors which I find unusual.

Therefore I would use datashet for the voltage regulator to make sure you coonnect polarety correcly.
sneak-thief
The + and - markings are incorrect. You connected the power wrong.

The left pcb trace which has a - written next to it is actually going to pin 1 of the 7805 voltage regulator, which is the positive voltage input. So that trace gets 9V.

The trace to the right of + is the ground.
bmot
Thanks a lot for your replies.

So I tried switching the polarity and this time it didn’t get hot, but I still can’t get it working, maybe it’s broken. Can anyone be bothered to teach me how to check using a MM? I bought one but never used it, as I didn’t quite reach my aim of gaining competency in electronics (as is clear here seriously, i just don't get it)

JLR, thanks for digging up that website. It’s not for this device, but funnily enough, it is for the other JL Cooper item I got in the same auction, it’s called the Micro Sync. I already have a Kenton so I haven’t tried this yet as i just don’t need it. i haven’t been able to find anything at all on the mini-midi cv, i wonder if it ever existed...
bmot
So a bit of progress, but weird. I can get my Micromonsta to go nuts, constantly changing patches and playing random notes, when I connect the leads the way it was suggested. I didn't even have any CV or gate connected. The dip switches also don't seem to make any difference. Any ideas?
Sandrine
Check the voltage after that 7805 reg, it may have been damaged. It should be putting out 5V. I don't think much more than -.6V would have been exposed to the circuit when was backwards so that's the only thing possible really
bmot
Sandrine wrote:
Check the voltage after that 7805 reg, it may have been damaged. It should be putting out 5V. I don't think much more than -.6V would have been exposed to the circuit when was backwards so that's the only thing possible really


If I'm reading it correctly it's putting out 4.04, should just replace it? I actually think I have a 7805 in my toolbox.
Sandrine
If that's the reading between the ground (tab on regulator) and the 3rd pin, yes it's cooked and that TTL stuff won't function properly at all with that voltage wink
bmot
Ok, thanks for the confirmation! I’ll change it put and see if I can get it working.
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