MaxiKORG DV800 CV/Gate mod ?

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schmidtc
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Post by schmidtc » Wed Dec 14, 2011 8:02 am

One for me please.

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andrewF
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Post by andrewF » Sat Jan 07, 2012 10:50 am

got boards in
built one
dragged my old 800dv out of the corner where it has been sitting unused since 2005 (just a panel & pcbs - no case or keys)
turned on the 800dv to find all the switches have corroded and need replacing (same as cykong had to do). Lower VCO doesn't work at all.
I suspect i will have to replace all the pots and electros too :party: to be honest it isn't going to happen for a few months.

so I tested the board by hooking it up to the PSU, feeding it CV and gates, then monitoring the outputs with my oscilloscope.
It all works as expected and is the same as the original e-labs design. The only difference is I used BC transistors instead of the Japanese ones specified. For this kind of circuit any general purpose trannie will do.

Each PCB has 2 CV circuits and two gate circuits, ie one PCB for one 800dv.
$20 each including shipping anywhere, pm if you want
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andrewF
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Post by andrewF » Tue Jan 10, 2012 12:11 am

boards sent today to

schmidtc
ndkent
kaoss
dougt

sent 11/1/12
jkjelec
a100user
Last edited by andrewF on Wed Jan 11, 2012 5:24 am, edited 1 time in total.

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a100user
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Post by a100user » Tue Jan 10, 2012 3:58 am

Out of curiosity, does anyone know if the 900PS uses the same circuitry and therefore this mod would work with that synth?

I beleive the 900PS predates the mini & maxi by only about a year.

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andrewF
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Post by andrewF » Tue Jan 10, 2012 4:15 am

They both have the same VCO chips, although the 900ps circuitry around the chip is a bit different. It looks like there is a 680 Ohm resistor in place of the 1k Coarse tuning pot on the 800dv (which is where the external CV is injected)
The 900Ps also has a similar trigger circuit to get the EG and whatever else to tick over.
So yes it would be do-able, just you will have to experiment to find the best way to do it.

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a100user
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Post by a100user » Tue Jan 10, 2012 12:36 pm

Thanks for that.

So can I have a board please?

Thanks
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andrewF
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Post by andrewF » Tue Jan 10, 2012 9:03 pm

no worries
pm'd

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dougt
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Post by dougt » Wed Jan 11, 2012 2:14 am

Could half of it work for the 770?

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andrewF
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Post by andrewF » Wed Jan 11, 2012 7:00 am

I am sure you could make it 'work', the question is how well?
Tho I remember when my 800dv did work the CV/gate mod circuit was great fun but difficult to tame.

It looks like the 770's "remote" input is a gate or trigger input, at least to trigger the EG. Otherwise, the gate sections on the mod PCB have three types of outputs (one follows the incoming gate, another is inverted and the third connects to ground when the gate is high) This covers all the usual types of requirements for gates so one of them should suit your needs.

you could try to use the two CV channels on the mod PCB to control the VCOs.
My suggestion would be to use an oscilloscope and monitor the likely points around the tuning pots to see where the voltage changes as you press keys up and down the keyboard. On the 800dv this ranges from 1V for the lower F key up to 12V for the top C key.
You could check this with a multi-meter if you do not have a scope, just hold the key down until you get a good reading. Once you have found a likely node, cut it, install a switch to select between keyboard or external input and give it a whirl! Not sure how good your electronics skills are, don't be shy to ask here or on the diy forum.

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andrewF
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Post by andrewF » Mon Jan 16, 2012 7:14 pm

here is the BOM and wiring info for the PCB
If there are any errors or anything is not clear, just ask
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CaptainZilog
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Post by CaptainZilog » Tue Mar 06, 2012 2:00 pm

Great board !

Do I need 2 of them if I want to control Synth1 and Synth2 independently ?

Thanks !
pm sent

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andrewF
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Post by andrewF » Tue Mar 06, 2012 7:28 pm

Hi Captain
Welcome to Muffs
i sent you some email
:party:

Rqckmounted
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Post by Rqckmounted » Sun Apr 08, 2012 7:47 pm

Hi everyone

10 years ago I was walking in the street and suddenly I have fund a Maxikorg 800 dv in the garbage !!
The keyboard was very ugly and painted in christmas green color. The synth has been put in storage since

now that I can across this nonlinearcircuits pcb board I am so excited to make this mod.

I have a basic knowledge in electronic so I would like some guidance please if someone can help.!

This is a list of the components / parts that I assume is needed, if there is anything else I need to get or to know please let me know.


100 nf capacitor X 6

100 k resistor X 10

10 k resistor X 10

1 k resistor X 2

diode 1S1588 OR 1N914 X 8

1x3 (AVR ISP header) X 4

1x2 (AVR ISP header) X 2

10u Capacitor X 1 what is the voltage ??

op-07 op-amp 78L15 OR 7815 X 2

10 k trim pot X 2

nun and pnp transistors, what are there values ??

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andrewF
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Post by andrewF » Mon Apr 09, 2012 3:38 am

Rqckmounted wrote:
10u Capacitor X 1 what is the voltage ??

op-07 op-amp 78L15 OR 7815 X 2

10 k trim pot X 2

nun and pnp transistors, what are there values ??
Hi
The capacitor can be 35V or higher (50V okay). I always buy 50V rating. This is just the minimum operating voltage for the cap.

Transistors are
NPN - BC547 (need 4)
PNP - BC557 (need 2)
any general purpose types will work, but be careful to check which way to insert them on the PCB. The PCB is designed to take the BC series

The 78L15 is a regulator, you just need one of these. Note the 7815 is a 1A version and is bigger with a different pinout to the 78L15 which is the 100mA version.

The two op-amps are TL072, many dual op-amp ICs will work fine.

http://www.taydaelectronics.com/ are a good cheap place to get almost everything

Rqckmounted
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Post by Rqckmounted » Thu Apr 12, 2012 8:56 am

Hi Andrew

Thanks for the info, I will take my time to do this mod, I will let you know of the progress.

Best regards

Dave

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analoglsd
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Post by analoglsd » Fri Apr 13, 2012 4:15 am

I'd like to buy one of the PCBs if they're still available.
Thanks.

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andrewF
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Post by andrewF » Fri Apr 13, 2012 4:34 am

pm'd
8 left!
Though once they are gone I will probably get more, its a small PCB and easy to tack onto other manufacturing runs.

Rqckmounted
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Post by Rqckmounted » Wed Apr 18, 2012 1:11 pm

OK everybody

Now I am ready to order my electronics components, please note that I have put more quantity than need to be shure to have spare parts to keep…

here is my list:


BC547 Transistor NPN 45V 0.1A x 5

BC557 Transistor PNP 45V 0.1A TO-92 BC557B-KEC/P x 3

10uF 50V 105C Radial Electrolytic Capacitor 5x11mm x 2

100nF 0.1uF 100V 5% Mylar Film Capacitors x 7

100K OHM 1W 5% Carbon Film Resistor x 20

1N914 Small Signal Diode 200mA 100V x 9

L7815CV L7815 7815 Voltage Regulator IC +15V 1.5A x 2

TL072 LOW NOISE J-FET DUAL OP-AMP IC x 3

10K OHM Trimpot Variable Resistor 6mm x 3

40 Pin 2.54 mm Single Row Pin Header Strip x 1

10K OHM 1W 5% Carbon Film Resistor x 20

1K OHM 1W 5% Carbon Film Resistor x 10

L7815CV L7815 7815 Voltage Regulator IC +15V 1.5A x 3





Question no 1

The 100 nf capacitor I have found are in Mylar or Polyester material, I wonder if it make any difference if they are not in carbon ( Beige brun color ) !??

Question no 2

Is 1 watt are ok for all the resistors in my list ?

Question no 3

I did not found the 78L15 regulator so I will use the 7815, I am not able to see the pin out difference (only 3 pins) ??




Stay tune for the progress work

have a nice day

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andrewF
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Post by andrewF » Wed Apr 18, 2012 5:32 pm

Hi
1. the 100nF capacitor is just for decoupling, it keeps the power supply smooth. A ceramic (beige colour) is fine for this job, it is also fine to use mylar or poly. These types are better quality.

2. definitely not ok. You need 1/4W (0.25W) resistors. The 1W types will work but be too big to fit on the PCB. Sorry I did not state this :oops:
You can use metal film or carbon resistors, metal film are better, but seeing as the 800dv uses all carbon resistors (metal film used to be expensive) it will make no difference.

3. The 7815 will have to be installed backwards to the 78L15. Also the 7815 pins will probably be to large to fit in the thru holes, so you will have to solder it standing on the PCB, trim off the pins a bit so it is not too high, but don't trim off too much so that you cannot solder it easily. Remember if you use a 7815 it will not have a strong mechanical connection to the PCB so do not bend it around - be gentle with it 8_)
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rude66
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Post by rude66 » Wed May 16, 2012 4:14 am

i'd like one of these pcb's if you still have them.. would be great to use my 800DV again!

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andrewF
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Post by andrewF » Wed May 16, 2012 4:29 am

Hi & Welcome to Muffs

still have a few
will send you a pm (private message :mrgreen: )

GlennVS
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Post by GlennVS » Thu May 24, 2012 12:18 pm

I would like to order a PCB to modify my DV800. If I'm correct I only need 1 PCB for 2x cv and 2x gate?

Grtz

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andrewF
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Post by andrewF » Fri May 25, 2012 2:06 am

Hi
Welcome to Muffs

yep one pcb does the job

sent you a pm

Rqckmounted
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Mmmm Capacitors look pretty big for the PCB

Post by Rqckmounted » Sun Jul 01, 2012 4:57 pm

hello again

This is what I have received :

http://www.taydaelectronics.com/capacit ... itors.html

I was able to solder them on the PCB but they are touching each other (tightly) with the 7815 and the other black capacitor.

Should I go on or order smaller beige ones ? ( Can seem to find some beige caps )

Thank you in advance

Have a nice day

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andrewF
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Post by andrewF » Sun Jul 01, 2012 5:53 pm

if you mean the bodies of the components are touching, that is fine.
Just be sure there is no metal to metal contact.

Post a photo of them if you like.

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