first thread here, hope someone can help!
after owning a minimoog for 12 years now i got a micromoog last week and love the additional features
and the character it adds to what i´ve been used to so far.
regarding my technical experience.. i can´t really read electronical circuits.. only soldered quite some stuff
with help of instructions and own a multimeter at least.
i was able to fix some smaller things with the micromoog like a loose contact which brought the tuning pot
at the backside to life again, yes!
one rotary switch is very wobbly. (i was able to correct the wobbliness of to the two other switches).
but i guess the switches can´t get opened? when removing the cap, it got even wobblier.
(it doesn´t affect the function though)
the main thing not working is the s-trig input, all the other inputs work properly.
so.. i found a detailed service manual of the micromoog.. troubleshooting section says:
No Ext S-Trig + KBD Trig correct → IC204
I attached a picture of the board. i was able to trace the s-trig to the point of the transparent plastic connector
(marked a red dot on it) and ensured that the s-trig connector has contact up to this point.
Marked the IC204 as well with a red dot.
How to go on from here? there seem to be a few capacitors (and maybe other stuff) between the plastic connector
and IC204. Someone who could guide me what to do/try?
after measuring around a lot on the board i tried something different,
took a clock from the eurorack-modularsystem and after having inverted AND amplified it,
the micromoog gets triggered successfully!
when taking a normal jack (without the volt → s-trig mini-circuit) a much weaker signal is sufficient
in order to trigger it. sometimes it needs inversion then as well, sometimes it doesn´t.
so any hints what it could be?
I checked IC204
At Input B Pin6 i have 1,8V, at the output i have -13V. next station where the trigger-impuls goes
is the germanium diode CR202, where it still is at -13V, after the Diode it shows 0,0V,
but on Audio-Level there is still a very very weak clock signal audible.
Any hints how to go on from here?
I assume the micromoog “should” work with the exact same strig-signal as the minimoog?
if so there has to be an error within the circuitry
MC1458 dual op amp. Known to fail sometimes after so many years.
Easily found and inexpensive. It would be a good idea to install an IC socket, too, before installing new IC.
Ideally, you need a desoldering iron for this job (double side printed circuit board) to remove old IC204. Or you can cut its legs with cutting pliers for easier removal if you don’t have access to a desoldering iron.
Don’t heat the traces too long to extract the remaining parts of the metal legs with pliers (whilst heating them with soldering iron), so as to not damage the printed circuit board traces.
i got help the last few days at sequencer.de as well and finally found the error today
Replace IC204.
Easily found and inexpensive. It would be a good idea to install an IC socket, too, before installing new IC.
yes, i´d definitely use a socket, when replacing a chip, but it actually wasn´t the chip,
the failure was caused by R255 (a 680k resistor) which didn´t let go anything through anymore
and so pin 5 (ic204) wasn´t provided with +2V anymore.
as i already have this thread open… two other things..
is there a way to reduce the humm of the power supply at least a little bit?
and second.. what exact kind of material is the metallic parts of the side panel and how can i treat it,
in order to remove scratches/ get a less used look?
owning the micromoog for 2 weeks now i have to say.. what a great addtionto the minimoog!
lots of interesting experimental sounds to complement what the minimoog does!
i changed the thread-title to new topics still relating to the micromoog..
after having solved the s-trig problem, it turned out, there are two other errors..
when the micromoog gets controlled from an external keyboard, the intonation is wrong and i don´t know how to trim it.
(when i play the micromoog directly over its keyboard, the cv output gives out the correct cv-information.)
when controlled through an external sequencer, the s-trig output corresponds correctly to the s-trig at the input.
but the cv-input signal isn´t available at the cv-output at all in this case.
Is the micromoog hrtz or volts though? Not all moogs are the same.
thanks for questioning me i found out that the micromoog is actually quite an outsider having a 0,95V/Octave characteristic!
i followed the instructions of a german forum connecting a 10k linear potentiometer in series to the tip of the oscillator input and
adjusting it to 5kohm. now it is 1V/Oct!
too bad i had to realize now that the minimoogs cv-input doesn´t follow 1 v/oct very exactly as well, but on the paper it should..
(normally i control it via sequencer but as i have the micromoog now i´d really like to control them both from a midi-keyboard
to have monophonic minimoog/micromoog-superpower! (little bit outside-attenuation for the cv-input helps)
okay. number 1) solved.
one problem to go:
when controlled through an external sequencer, the s-trig output corresponds correctly to the s-trig at the input.
but the cv-input signal isn´t available at the cv-output at all in this case.
additionally i try to convert the s-trig output of the micromoog into gate output (in form of a normal jack)
and totally don´t get it:
shouldn´t really be too complicated.. i also made a cable from jack to s-trig which i use all the time.. strange!
in addition to problem number 2) i wanted to explain a little better what i tried converting s-trig out to gate out..
inside of the micromoog i solder the “tip”-contact of the male s-trig out plug directly to “C” of the specified transistor.
transistors “E”-leg gets connected with s-trigs ground-contact, which is also soldered directly to gnd of a female plug connector.
the “B”-leg goes through a 10k resistor and then to the “tip”-contact of the female plug connector.
now the female plug connector “should” give out a normale gate output shouldn´t it?
tried it a few times with different transistors.. didn´t get it to work.
when i touch the unmodified s-trig outs “tip” contact with the “tip” of a “gate-to-s-trig-cable” which leads to the minimoog,
the minimoog gets triggered after releasing a key of the micromoog (should be normal behaviour).
of course i also tested the gate output of the female plug connector mentioned before with trigger ins of my modular system,
but it doesn´t get any visible signals from there. quite a simply task to convert s-trig out to gate out.. i thought..
okay.. regarding the s-trig-mod not working.. seems to be more complicated and needs additional voltage..
if someone knows how to turn the s-trig output into a gate output, please talk
Gate (V-trig) to S-trig is a passive circuit like the one you attached in your earlier post.
S-trig to Gate (V-trig) is an active circuit needing power, etc..
thank you!
unfortunately the schematic is not very understandable for me (and my small skills) next to the writing.
if anyone has done this with his micromoog and has a better schematic, this would be really great.
question is also if/where i can directly tap voltage from the micromoog itself
To be honest, if you can’t understand that little schematic and aren’t sure where to obtain the voltage you need to run it - you shouldn’t be attempting anything like this..! You’ll end up with a synth that needs much more work putting right any problems that you will inevitably cause…
thanks for your help, but the schematic is not really readable very well,
apart from my little technical understanding i can´t really identify every letter.
You’ll end up with a synth that needs much more work putting right any problems that you will inevitably cause…
i won´t do it unless having figured out how to do it right
i repared the s-trig-problem (with help from some great people) and a few other minor things and am careful as hell
in general when it´s about modifying/repairing old stuff.
soldered a baby animal 4 channel-microphone preamp. i can´t remember having destroyed anything so far..
so with good detailled instructions i don´t see a problem getting things like this done as the schematic actually looks quite simple.
so, still happy for anyone coming with a detailled instruction complementing this schematic.
i really don´t want to waste your time or annoy you Tom! Your schematic is a great starting point! thank you!
OK you could build this circuit into a small plastic project box and power it from a 9volt battery…! probably safer…
Any small PNP switching transistor would probably do it… here they chose a 2N2222A. You also need two 10K and one 100K resistors and a small diode - a 1n4048 would be ideal.
You need to be sure which leg of the transistor is emitter, base and collector (google it…?) and also which way around a diode points.
Join together a 10K and a 100K resistor.. the join is your S-trig input. Add another 10K resistor to the other end of the 10K already used. The join between the two 10K’s here is your power +ve. The other end of this 10K goes to the transistors collector. Going back to the 100K resistor… the free end goes to the transistors base. The transistors emitter goes to ground. Where the second 10K resistor meets the transistors collector you need to attach the anode (the end without the band) of the diode. The diodes other end (Cathode) is your V-trig output.
Wire it all up to two jack sockets marked IN/OUT and just patch it into your trigger line. Safest way to go…
thank you very much tom!
in connection with the schematic it´s now totally understandable!
yes finding out the transistors legs/diode polarisation is no problem,
also i looked up the symbols now to be able to comprehend the schematic
can i use the micromoogs output sockets for wiring to “ground” ?
i can test it this way with a battery.. that´s perfect. having done that, i´d be curious how to use
the internal power to supply it.
i guess the +15V connector would be too strong then and i´d first have to reduce it to 9V?
how would i do this? as i have to look for the parts anyways it would be great to be able
to buy parts need for this “task” as well.
edit: i couldn´t find a source for 1N4048. not one result at ebay for example.
do you have an alternative which might be a little bit more common?
(little bit outside-attenuation for the cv-input helps)
