[SOLD] Selling my “itchy trigger finger” Yamaha RX21..

That’s right. The RX21 I bought in a moment of “Buy-it-now” madness is for sale. I’ve had a play with it and it’s fine. Backup battery is working, as it saves whatever I program into it.But it’s not for me. Grab yourself a bargain. (Check out the front page for details)

Dr-55 Project Update

Just a note to say I have found the fault with the 4011 replacement: I tested all 14 pins on the IC socket after removing the chip and.. one of the pins does not beep on the meter.. how can an IC socket not have continuity from top to bottom?

Anyway, it doesn’t, so I need another socket.
Maplins in Middlesbrough is still trading, so I’ll give them a try..

This message was sent from my phone. Please excuse the brevity and any typos. Thanks

[SOLD] Synteknik News Update: Electribe sales | Itchy Trigger Finger Syndrome: Mattel Synsonics

Electribe Sales:

I have now sold both my Korg Electribes (EA-1 and ER-1).  I got £125 for each of them, and I have to say that it was MUCH easier to sell the ER-1 (drum machine).

Here’s a selling tip:  include the spec from the Korg website in the listing. I was on the second relist for the EA-1 when I added this, and it sold for the full amount an hour later.

Mattel Synsonics:

My “Itchy trigger finger” went off again.. this time I bought a “broken” Mattel Synsonics Drum machine.

I’ve always liked these things, but as I remember, the last one I had was very noisy and I didn’t have any way to shut it up at the time.. Pretty sure I sold mine to Shaun, at dubsounds.com, who was compiling a huge collection of drum machines, for sample pack creation.

Anyway, that was then and this is now.  The machine would have been delivered on Easter Saturday, IF I’d been in at the time. Nobody else could be bothered to answer the door, so now I have to wait until Wednesday, which is the only late opening for the sorting office.

The one I just bought is rough and non-working, so we’ll see how I get on with that,

No Work Done:

I’ve done absolutely NOTHING on ANY of my projects, (DR-55 / SR-99 / Korg Delta / EK-2). I really MUST get a grip. There are other machines in storage as well.. (M500, SH1000, CZ3000, Big Roland Thing).. the big Roland thing is getting in my way.


Oops. I bought another dr-55..

Yes I know. Itchy trigger finger on the Buy-it-now button..

This one is a bit scruffy, rusty battery cover, and from the description it looks like another 4011 transplant.
Hopefully I can turn this around before I go off to Bulgaria in a couple of weeks. Already got a 4011ube and a 5501 just in case.. possibly an IC socket as well.

Boss DR-55 capacitor change to allow use of TC4011B chips..

From a thread on electro-music forum:

“The CD4011 is a bit fussy … a few years ago I repaired one of these machines with a bad 4011, and the replacement I used caused pattern writing to work incorrectly. A different 4011 fixed the problem.”

“I had the same problem for long time until have found the solution.
Is easy to fix it changing C46 to 10NF cap, an will work with any 4011 series.
In the service manual they say “machines with SN up to 923500 CD40UB only”. this is because the propagation delay time of this chip is faster than other 4011s (a half) and the delay formed with Q16 C46 etc is not enough to feed the flip flop and the memory on time (must be double).

I came across this extremely useful piece of information while researching this project.

Many thanks to electro-music forum for this one!

Hohner EK 2: All sounds now working. Just about..

I spent an hour tinkering tonight..I now have all sounds working: piano, harpsichord, electric piano, bass, brass, and.. tada.. strings. Piano was a wobbly connector, and strings have a dodgy capacitor on the crescendo function (I think) Turned that off, and.. beautiful strings..
Still need to replace a load of sliders and sort out a combined stereo output. I may have found a source for spares, too.

Hohner EK2 – First Look

I almost called it a synthesizer.. but really,  it’s not. But it IS analog (“analogue” – in English) and it has a “Strings” section.

In fact, it has several “sections”:

Piano (not working)

  • Piano
  • Electric Piano
  • Harpsichord

String (Very quiet)

  • Strings

Brass (Working)

  • Brass
  • Mute

Bass (Working)

  • Bass

The complication here is that there are two mono outputs (labelled as stereo on the back, confusingly). Brass only appears in the RH channel. Strings are on the left channel, but way too quiet. Bass is on both, I think.

The seller said that only the bass worked, so I think he only checked the left channel. I’m either going to add a “combined” output (stereo jack), or make up a lead that does the same job.

The piano presets light up, but nothing comes out.  I REALLY want the strings to work, as that’s what I bought it for. The brass works and is loud, but the release doesn’t do anything.

I have been in touch with Hohner, who confirmed that it’s really a re-badged Italian machine (Excelsior, maybe made by Elex).

That was what happened with the previous Hohner I had, years ago. (That was a monster). Unfortunately, there is no documentation on this machine available.. There is a really good Youtube video of someone playing an (Excelsior) EK 2..

Physically, it looks it’s age (1970s), and a lot of the sliders have their stems broken off. One slider is not visible from the outside.  I should be able to source similar sliders and get this thing going again.


Introducing my new Hohner International EK2 Synthesizer project..

I just bought a Hohner EK 2 synthesiser!This will be my main project after I finish the Korg Delta.
I am pretty excited by this, although I know only the bass section currently works. I am familiar with this kind of technology so it’s not that scary, although I did have a Hohner string machine years ago that I never managed to fix .

Images to follow .

EDC SR-99 Project – TC5514 memory chip replacement.

I finally got around to replacing the memory chip. I bought two from vintage planet on ebay.co.uk (Hi Senso!), which arrived very quickly. Unfortunately so did the ‘flu..

Anyway, I whipped the memory chip out using my usual Duratool Soldering kit and desoldering pump. 5 minutes max, I’m getting good at this now!

I was so quick that I installed the 18-pin IC socket as well. 10 minutes max, including re-soldering and wiggling..

So,  the acid test: did it work? No. So I popped the original RAM chip back in and tried it again. Nope.

The problem appears to be that I can’t get the thing into “Write” mode. No amount of fiddling seems to make it work.

I don’t have a schematic for this, and it’s NOT the same as a DR-55 or SR-88, so I’m a bit stuck.

Can anyone help?


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EDC SR-99 Project – Introduction

This may or may not be the SR-99 I replaced the battery clip on in an earlier project.
There’s a video associated with that: https://www.synteknik.com/samples/edc-sr99.3gp

Anyway, although it appears to work, there’s no sound (there’s none on the video either..).

I’ve had it in bits, and although I can see a replaced 4011 sitting in a socket (not usual), I can’t get any sound out of it. It appears to program OK, though..

The SR-99 uses a TC5514P chip instead of the DR-55’s TC5501P, but it’s the same principle, so I checked the output pins when the sequence is running, and all four pins are high and stay high. That’s wrong, as they should only go high when there’s a sound. So it’s probably a bad memory chip.
I have two on order from vintage planet as I write this…

Related forum links:

Music Electronics Forum: http://music-electronics-forum.com/t45826/

Dubsounds: http://dubsounds.proboards.com/thread/3093/edc-schematics-service-manual-needed

Electro-Music:  http://electro-music.com/forum/viewtopic.php?p=432562#432562

Vintage Synth Explorer: http://forum.vintagesynth.com/viewtopic.php?f=1&t=104505



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