[sdiy] EKO Stradivarius

[Jean-Pierre Desrochers]

Hi Rutger,

For the first ‘connected’ tests you could run your power cord in series with a 25 watts or lower wattage bulb.
If there is a short (which I believe there is) the bulb will lit brightly to show excessive current draw but preventing any damage
to the shorted circuit. Then you can go further to spot the offending short..

 

De : Synth-diy <synth-diy-bounces at synth-diy.org> De la part de Rutger Vlek via Synth-diy
Envoyé : 27 mars 2022 13:12
À : SDIY List <Synth-diy at synth-diy.org>
Objet : [sdiy] EKO Stradivarius

 

Dear list,

 

for reasons of knowledge (and instrument) preservation, and out of enthusiasm I wanted to share some info on my current restoration project. A few months ago I saw an ad listed on internet for an Eko Stradivarius, which I didn't know, and by the looks of it assumed it to be a cheap/cheesy kind of organ. I remember skipping over it, thinking "that's one heck of a pretentious name for an instrument". Shortly after that I was watching this documentary on Italian synth industry: https://www.youtube.com/watch?v=FZ-sVujDlS8 and was amazed at the sounds of some of the more obscure Italian machines (I owned a few less obscure Italian instruments but was never impressed with them). It brought me back to the Stradivarius, and after seeing a short video of it, I realised it was an amazing sounding string ensemble, easily on par with (and technically very similar to) the first version of the Solina. Luckily, the instrument was not yet sold, and I managed to buy it at a very decent price. Optically, it is in a very good condition, even the original lid was still there (despite the tolex no longer sticking to some of its corners), and it was fully functioning!

 

Arriving back home, I opened it up, wondering what to find inside. The first, and best surprise was: a service manual with full schematics stitched to the inside of the case! Since this instrument is so rare and I could not find any technical info online, I decided to scan and share it with you (assuming that any legal restrictions are long overdue). EDIT: attatchment turned out too big for this list, so available on request and submitted to synfo.nl <http://synfo.nl> .

 

Internally, the instrument seems to be in fully original state, including a gigantic amount (126!) of electrolytics that are probably several decades beyond their expected life, but show very little sign of leakage or bulging. I wondered, since there are so many, if I could leave them in place, but decided to replace them as I want to give this instrument a much longer life. Many of them are axial capacitors, by the way, which are much harder to come by these days (especially when you want a decent brand). I was wondering how others go about this? Replacing them with radial versions could mean more physical stress to the legs of the radial ones. Would that be a problem?

 

After finishing my shopping list for capacitor values I took a brief glance at the power inlet, wiring and fuse holder, which generally looked tidy except for mains insulation that was stripped back a little too far to my taste, leaving bare copper to be fairly close to the metal casing. I almost decided to go for lunch, but then thought a quick check of the fuse couldn't harm, even though the instrument was working fine, so I expected no problems... well aaaarggh! Glad I checked, because I found an example of the worst kind of electronics practice: aluminium foil wrapped around a burned-out fuse, creating a bypass for it without any current limitation whatsoever. After seeing that I was glad I had decided against using the instrument much, until at least all PSU electrolytics were replaced. Also, I'm curious what will happen to a newly inserted fuse at the proper rating, if there's a hidden malfunction that will trigger it.

 

Rutger

 

 

 

 

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