Repairing an Elka EM22

[next to nothing]

As i've mentioned in another thread, i've dug up my old Elka EM22. i bought it 10-12 years ago, and it has basically been hidden away in my basement.
Im considering trying to fix it. When i bought it, it seemed that the former owner had put it in for service once, as one of the chips was marked "def", which i interpret as defective. The chip is marked in the attached picture, and the service manual describes this as a "192 word x 8 bit cmos static ram".


symptoms:
I have it hooked up to my daw, and fed it with chords and arps, with constant velocity. basically, the notes seems to play at varying velocity, and sometimes not at all.It has 6 voices, and a 1+5 split mode, and the issue seems to be consistent on both parts (arpegging the bass will miss a voice here and there, chords will miss a voice or play the voices at different velocities). symptoms are similar if i just arp the bass, just play chords, or combine the two.

My questions:
1. Im not very familiar with instrument electronics. I know my way around synth basic theory, but at hardware electronics i am totally blank. So can anyone tell me if the the chip i mention being broken would result in the symptoms i have noticed?

2. If this chip might be the culprit, i did some googling and found a supplier that seems to be able to supply a spare, see https://www.utsource.net/itm/p/1097270.html . I notice the pictures they supply has some different numbers on them, but if i supply them a picture of the chip in question and they send me a replacement they say will work, would it be safe to just swap it? Maybe someone can recommend a different supplier?

3. I bought this thing for 60 bucks long time ago and i am unsure of how much this thing is worth, and therefore how much resources i should spend getting it up and running properly. I see there is one up for sale at the moment, but googling the sellers text reveals it is a copy of an ad from 3 years ago, so i am not sure if it is a realistic price or if the seller is real at all. Anyone have any experience with pricing this kind of stuff?

It seems to sound pretty good when working properly, so i am kind of motivated to get it up and running
https://www.youtube.com/watch?v=PsujMf8sQzY

Resources:

thesuspect.jpg (371.27 KiB) Viewed 5507 times

chip.png (35.52 KiB) Viewed 5507 times

[next to nothing]

Well I have had some educated input that my prime suspect probably isn't the guy to blame. I will continue my research, but if anyone have input, please feel free to chime in

[Marco]

This is a really great machine. Like poly 800 or siel dk 80 with ssm chip

[next to nothing]

It also apparently has much in common with the Oberheim matrix 1000 (not the modulation capabilities though) and the matrix 6 as it uses the same chips for voices, and the analog stereo chorus is supposed to be really good.
I have been talking and getting some input from some competent guys, and the bad news is that the problem most likely is with the voice chips themselves (cem3396). The good news is that they might not be that pricey, I have located a source in France that apparently will sell me a set of 6 chips for 80 euros. I have sent an email to check if they have them in stock. But first, i need to slaughter this box a little bit more so i can re-seat the existing ones, and switch them around so i can see if they indeed are the problem. One might be bust allready, the others might be failing, and if the pattern of dropped notes etc. is coherent with how i switch them around, they most probably are the issue.

[cortone]

If you are planning on doing this yourself, your first step should be to check the continuity (fully soldered down to the pads on the board) at all of the connections of the chips with a multimeter. If you have schematics for the chips, and can access them under power, you could also check that the ground and voltage inputs are good and registering the correct values. Include the questionable RAM chip in the process as well. If you have a way to check them, any "clock" chips should also be evaluated because a slightly erratic signal from one of these could create the result you are describing, although a multimeter isn't much help here beyond checking the continuity and voltage/ground. It can't help with the quality of the clock signal (oscilloscope for that).

It sounds like you are getting excellent advice, and apologies if I'm suggesting things that you have done already, I'm not clear on your exact skill set. Swapping the chips around has some inherent risk, and it's possible to create more issues than already exist if you aren't careful.

If you do get to the point of swapping the chips, you should consider changing the ram chip as well, depending on cost, etc. just to be sure.

Sounds like a fun project with a great payoff if you're successful.

Cheers!

[yayajohn]

Not sure if jhulk is still around but he did some nice work on an old yamaha PCB board of mine. First thing he did was replace the chips with sockets for easy swapping. You might want to try that if you are going to be moving the chips around.

[next to nothing]

No need to apologize, i need all the help i can get
Thanks for the advice, i think i have the complete schematics, although i haven't checked in detail. I do have the pin layout for the chips, so it shouldn't be a problem to identify the ground pins etc. To clarify, i am a novice when it comes to electronics, but i do have have basic understanding/education in the subject, although it hasn't been practiced for, what, 20 years? So regarding powered down systems i think im ok, although i am a bit skeptical to fiddle around with currents running
The risk of swapping around, is the main concern mechanical damage?
Regarding the ram chip, i have traced one down for less than 3 dollars+pp, so if i can verify that it will be compatible i will swap that one too.
My original plan was to this myself, of course that was when i had identified the ram chip as the problem. I think my revised plan is to first do a visual check of the chips to see that nothing has popped out during moving, buy a multimeter (i guess that describes my skillset ) and check the connections. If mechanical damage is the main concern with swapping the chips around i will probably do that as well, i guess its the same hazard as fitting new chips?
I am also thinking of tracing down some local synth doctor after i have done the basics, especially for things that needs to be done with the unit powered up. I probably should do that first, but i think it would be a good learning experience to at least dig in a bit myself first, as long as i am not risking doing much damage.
Found another video that compares it to other "similar" synths, and i like what i hear, so thats a great motivation
https://www.youtube.com/watch?v=UsFfqyRhLo8

[next to nothing]

yaya, i was thinking of messaging jhulk, i'll send him a PM. Thanks for reminding me
Hope your REV2 is keeping you occupied

[cortone]

Yes, mostly worried about mechanical concerns. Frequent soldering/unsoldering can be problematic to both the chips and the board with respect to heat if you're not skillful, and any solder bridges that mis-connect the wrong pins can be disastrous. Breaking off pins is a concern as well. Of course, I'm assuming they are soldered down and not already socketed.

I also forgot to suggest a careful look all around the board for any places that look burnt, or disconnected, and careful attention to any caps (the upright barrels and brown disc components) that are leaking/swollen/bursting or just disconnected somehow. I doubt that you will find anything based on the functionality that you describe, although a failing cap could be the source of what you describe if it is part of the circuit with the sound chips.

[next to nothing]

Luckily the Elka is very serviceable from what i hear, all chips are allready socketed, not soldered, so that limits damage potential
And i will also go over the caps for leaks, thanks for the tip.

[dawman]

Sounds Great.
The reason it’s chorus is so Clean is its Freeform and no retriggering from a separate LFO/EG.
It’s what I heard at least.
I use Scope DSP, Hardware and Pedals to avoid retriggering.
The chorus should carry over phrasing like water.

Think you got a great synth there.
I remember every Elka I ever heard was pretty fat.

[next to nothing]

Well fuck me sideways.

So i dismounted the top circuit board today

chip1.jpg (206.37 KiB) Viewed 5397 times

And guess what....

chip2.jpg (85 KiB) Viewed 5397 times

So this little fucker wasn't completely fitted in its socket! I took it out, straightened some pins that was clearly bent, re seated it, and hey presto, I have a fully working 6-voice analog italian synth
Sorry for the boring project

For reference, the source in french has new, old stock CEM3396 chips in stock, a set of 6 is $120 so i might order this so i have spares for later. http://www.maad.net/ms6/

I have currently just tested it on the headphones out, which is a bit loud and noisy, but i might post some sound snippets when i get it hooked up to my daw. Thanks for all the tips!!

[yayajohn]

Sweet! Love it when it's a simple fix. Like finding buried treasure. Enjoy, hope to hear what it sounds like.

[next to nothing]

Just tested the line outs. Smooth as silk. It's a rather tough cookie to program, especially since the scope drivers midi aren't multi client, so i cant use the free software editor while having ableton live up and running, which sucks (crossing fingers for next Scope release). But it sounds great

[petal]

But it sounds great

Show us - don't tell us

[cortone]

Well, it was fun while it lasted!

Glad it was that simple to sort out, the options were much less appealing. Have fun!

[Marco]

Gratulations! And now Party and we want a mp3 with a elka Sound including!

I have this old siel dk 80 ssm machine

[next to nothing]

But it sounds great

Show us - don't tell us

OKOKOK!
Well, as i said it is a bitch to program, and i am currently on a 2 octave keyboard so bear with me
So as i am basically stuck on preset surfing (even that is hard), i just trew somethng together which isnt all knobtwisting (well, there are no knobs to twisr, iand i havent figured out how to get it responding to midi automation). All sounds from the EM22, a little delay and reverb added, no eq, no mastering, very lacking quantization... Take it for what it is.

[Marco]

Good demo. Are all the sounds from the elka?

The elka is very similar to the siel dk, there are the numbers of CCs written directly on the chassis. If you had a behringer bcr2000 or any other controller then you can operate and treat the sound just the way you like it.

Resonanz is 53 and cutoff is 52

[next to nothing]

Hi Marco, thanks for the nice words.
Yep, all the sounds are from the Elka. I guess you might be curious about the guitar, if that is the case i used the MS3 as a midi plugin to drive a guitar preset, added some Waves 6-tap delay and a bit of Tal Reverb 4 . The MS3 works wonders for strumming like this, and it is free http://www.vst4free.com/free_vst.php?pl ... er&id=2388
I dont use any sound from the plugin, just the midi output.
Regarding the midi, i have the page you posted, thing is i draw curves in Ableton Live and the Elka doesn't respond. The software editor for the synth use SysEx, and it responds to that, so i don't know... I guess I'll figure it out in the end