repairs, modifications, schematics etc.

nothing very fancy, just various stuff i've documented that others might find useful. i don't really have any schematics that the internet isn't full of already, so this page will be mainly about repairs or modifications.

6 july 2014

A friend asked if I could look at one of his old synths, and turned up with one of these damn things:

The Formanta EMS-01. It couldn't be more Soviet-era if it tried. Took two large men to get it up the stairs. Synth section didn't play in tune, some of the organ presets had a crazy howling on top (sounded great by the way). Drove myself nuts trying to trace problems (there must be a hundred meters of wiring in there - all white). All chips marked in Cryllic, which I can't read. For something as heavy and clunky as it is, everything inside is really fragile.

Long story short, the usual capacitors in the power suppy were to blame, replaced them and it works just fine. Not without much grinding of teeth though...

how did this leave the factory in this state i mean really

culprits

funky Soviet SMD chips

aww look at the cute trimpots

experimenting with replacing the weird opamps, needless to say it didn't work.

Also put 1/4" jack outputs/inputs on the back to replace the DIN sockets, for some reason used on most Soviet audio equipment.

I'll try and get some sound samples of the thing up at some point...

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Mikko came around with a TC Electronics EQ from I guess the 90's - somebody liked their clear sticky tape - the transformer was bangin' around inside the box.

more tape

simple fix though, just anchored all that stuff down.

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Old Dynacord tape delay I got a few years ago - was distorting and not in a good way - usual culprit of power supply capacitors being shot. Sounds way better now (although no matter what it colours the sound of the guitar so I made an effects loop box for it, on the guitar fx page).

before

after

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I've had this Stageline mixer for almost twenty years. It sounds pretty awful (noisy as all heck) but is a part of the setup I use in the experimental electronic band. Over the years it's gotten individual channel phantom switching, a few extra main outs, a recapping/added decoupling caps for the opamps, and buffered post/pre fader direct outs. It's probably been cleaned more times than my fridge.

 

20 feb 2010

schematics for the modular volt/audio meter. very simple really, all directly out of the opamp datasheets. the meter clocks in at 3 kiloohms, hence the 3k resistor there at the end.

april 17 2006

sh101 external audio input modification

seeing as what i've been asked a few times how to make the external audio input for the roland sh101, here it is. the schematic, written on the obligatory napkin:

 

point A is to the amplifier section. point B is a direct injection to the cutoff frequency slider. i have them marked as 'on' and 'off' on the case itself, for some reason. below are a few internal shots.

as the astute will notice, i've taken two wires to ground where one would have been enough. this whole mod can be done in about an hour, but i'm sure i used a lot more time.

this modification is from some place i found on the interweb years ago, but didn't save the link and can't find it now. if you feel you deserve a credit, by all means contact me.

 

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