Author Topic: 18V Electric Mistress with reworked LFO & VCO  (Read 8649 times)

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #60 on: May 29, 2020, 04:43:54 PM »
I have updated the build document information on setting the clock trimmer.
Aurae kindly provided measurements of the sweep behaviour of his V2 EM (1ms to 12ms when Range Pot is at maximum) and I was
pleased to find I had the same sweep on my MN3207 build :)
To set clock trimmer, FM mode with Range pot at maximum should give clock (measured at pin 2 of BBD) of 42.55 kHz (about 23.5 uS period).

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #61 on: May 30, 2020, 12:03:06 AM »
I found an error in the schematic at the very start of this thread (a wrong component value).
I didn't correctly document what I had actually built with the SAD1024 circuit, and that schematic error then made it into the MN3207 design and build.

In the MN3207 schematic, R21 should be 5k1 instead of 5k6.   This change affects required component values in other places, namely the ratio of R32:R31.   So the MN3207 circuit needs the following two resistor value changes:

R21:  5k6 --> 5k1
R32:  220R --> 180R

If anyone has already done a build, then those changes can be made by adding resistors in parallel to the old values.
    5k1 ~  ( 5k6 || 56k ).
   180R ~ ( 220R || 1k ).

With these 2 resistor value changes (and a clock trimmer readjustment), the sweep range on my build with Range pot at maximum goes from 1ms to 12 ms as before.  So why make the change?
The difference is that with the Range pot at minimum, it will now sweep slightly higher (i.e. under 1ms) which is what happens with the original V2 EM.  Using a value of 5k6 would not let that happen.

I won't keep posting schematics. I will just update the schematic and parts list in the build document:

https://1drv.ms/b/s!AvrH61utWEtEjig_4U8k7-fGwkbv?e=69cQg1
« Last Edit: May 30, 2020, 12:41:34 AM by DrAlx »

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #62 on: January 17, 2021, 03:09:15 PM »
Here's a vero layout of the latest version (Revision 7) in the build document (https://1drv.ms/b/s!AvrH61utWEtEjjKUFA56edLu66rO?e=KWptlq).
Note some tracks near ICs are broken between holes rather than on holes.
The easiest way to make those breaks is to use a sharp knife to make two close parallel cuts and then lift out the bit of copper in between.
It's also a good idea to keep the two tracks to the Rate pot really short rather than have them as long strips.

« Last Edit: January 19, 2021, 08:35:56 AM by DrAlx »

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #63 on: January 19, 2021, 03:26:48 PM »
Oops repost