EHX Microsynth Mods?

[devnulljp]

Just bought an old v2 EHX Microsynth. Replaced the broken sliders last night (ended up just replacing them all for good measure) and a couple of dodgy looking electrolytics.
Got me thinking about other mods. I'd like to TB it and make the LED an effect on/off instead of just a power indicator.
I did that ages ago to my QTron based on this thread: https://www.talkbass.com/threads/ehx-ba ... mod.315187

But this version is different, with a DPDT and built in AC power supply. Can anyone walk me through it?
I've also heard about a mod to make it more bass friendly, but haven't found any kind of other info.

[moose]

I hate working on these things but that's neither here nor there. There's four part difference between the bass and regular versions and it's definitely a good mod. Hopefully the numbers below are referenced right. The expression pedal mod for the stop frequency looks great as well must try that out. Shogun effects has some demos of that here: http://www.shotgunnmods.net/EHX_BMS_Mods.html

The later units have the same pcbs so they just stick 24V DC from the wallwart into the bridge rectifier and regulate the working voltage, think that's +/-12V. The bridge rectifier blowing is a fairly common fault in my experience with 3 out of 5 that I've repaired have had to have them replaced. Rather than true bypass mod I juts hardwired always on and use a separate true bypass box so the MS can be kept out of the way and more importantly not be stepped on all the time.

ehx bass microsynth partslist (I deleted a bunch of it and just left the resistors and caps)

parts marked with * has differences between the bass and guitar version.

resistors:
r01 68k
r02 4k7
r04 470
r05 13k
r07 2k2
r08 3k3
r09 33k
r10 10k
r11 10k
r12 7k5
r13 15k
r15 3m3
r16 27k
r17 2k7
r18 27k
r19 560
r20 3k3
r21 2k2
r22 22k
r23 47k
r24 1k
r25 22k
r26 820
r27 4k7
r29 8k2
r30 2k2
r32 390k
r33 330
r34 2k7
r35 10k
r37 13k
r38 22k
r39 120k
r40 6k8
r41 220
r42 820k
r43 1k
r44 330k
r45 470
r46 3k3
r47 3k3
r48 10k
r49 220
r50 6k8
r51 10
r52 220
r53 47k
r54 47k
r55 3k9
r56 47k
r57 27k
r58 470
r59 470
r60 27k
r62 12k
r63 10k
r64 10k
r66 3k3
r67 820
r68 1k
*r69 12k 2k2 -> guitar
r70 22m
r71 680k
r72 1k
r73 2k2
r75 3k3
r76 8k2
r77 47k
r78 1k
r79 3k3
r80 8k2
r81 47k
r82 1k
r83 3k3
r84 8k2
r85 47k
r87 330k
r88 47k
r89 4k7
r90 1k
r91 470
r93 3k3
r94 820
r95 4k7
r96 47k
r97 1k
r98 47k
r99 47
r100 22k
r102 8k2
r103 820
r104 1k
r105 1k
r106 15k
r107 5k6
r108 1k
r109 12k
r110 4k7
r111 680

trimmers:

r03 10k pre amp gain
r14 100k squelch

capacitors:

*c08 2.2uf el 1uf el -> guitar
*c09 1uf el 0.47 el -> guitar
*c10 0.1 0.056 -> guitar
c11 1uf tant
c12 0.47 tant
c13 0.082
c14 1uf el
c15 0.047
c16 4.7uf el
c17 0.0033
c18 0.1
c19 4.7uf tant
c20 4.7uf tant
c21 0.1
c22 0.0033
c23 1.0 el
c24 0.082
c25 0.0033
c26 0.0033
c27 0.0033
c28 10uf tant
c29 1uf tant
c30 10uf tant
c31 100uf/35v el
c32 10uf/25V el
c33 10uf/25V el

From here: http://freestompboxes.org/viewtopic.php?f=13&t=7502

[Scruffie]

Well, much as I hate seeing mods done on vintage EHX if you're going ahead anyway there's some in here http://hammer.ampage.org/files/Device1-6.PDF

[Gemma Thrush]

Well, much as I hate seeing mods done on vintage EHX if you're going ahead anyway there's some in here http://hammer.ampage.org/files/Device1-6.PDF

this is cool - thanks for posting.

[Scruffie]

Well, much as I hate seeing mods done on vintage EHX if you're going ahead anyway there's some in here http://hammer.ampage.org/files/Device1-6.PDF

this is cool - thanks for posting.

It would be but I posted it without reading the first post properly, these mods are for the V1 not V2

The input impedance, attack decay sensitivity and the filter trigger mods are still applicable to the V2 but they wont be in the places that the article states.

[devnulljp]

I noticed that too. But thanks for posting.
Might not mod it, but would be nice to know how -- big thing I'd like to do though is the TB + effect indicator thing, replace the switch with a 3PDT and have the LED go on when the effect is active instead of just when it has power.

[Scruffie]

Okay well you just need a standard 3PDT wiring diagram, the input jack connects directly to the circuit input so you know where your Jack In & FX In are for the 3PDT.

Then on the SPDT switch currently in the pedal, the common pole goes to the output jack and you just need to work out from the other 2 wires which wire is the effect out (should connect to pin 1 of an EH1048 chip) and which is the preamp out which you no longer need.

The LED should connect through a 680R resistor on the board at one end and to a ground point at the other end, lift it from the ground point, run the ground point to the designated pole on the 3PDT wiring diagram and the lifted LED lead to the LED pole on the switch.

[devnulljp]

Thanks!
The LED doesn't connect through a resistor -- first time I've seen that. It's hooked directly to the built in power supply, which is where my confusion comes from.

[Scruffie]

Can you post a picture of how it's wired? It must connect through a resistor somewhere.