Gakken SX-150 problems.

Years ago, I bought a non-working Gakken SX-150. Tonight, I finally got around to trying to get it working.Switching it on lights up the led, so that’s a good start. However, there’s no sound output. Either via the built-in speaker or the "output" socket.
I’ve had the meter on the innards, and there is power to the board. There’s a voltage difference of about half a volt across the Variable resistor track, and the end of the stylus is about 3 volts
I’m a bit stuck now.. no amount of fiddling with switches makes any difference.
I’ll do a bit of research and see what happens.

[Tag SX-150, Projects]

Another DR-55, and a couple of Soundmasters, added to the list..

Found a box in the garage containing a (dead) DR-55, an SR-88 (untested), and an ST-305 (untested).

SO, I now have THREE DR-55s (at least), one of which works. Also, an untested SR-88, broken SR-99, untested ST-305 (I suspect broken, because it’s in the same box..)

This was lurking behind a BIG (dead) 90s Roland, the EK2 and the CS1000.  Must DO something about those.

There is also a microKorg chassis lurking in there (with keyboard). Forgot about that.

There is also a (working) Roland SH1000, (working) Korg m500, (dead) Maestro Rhythm Jester, and god-only-know what else..

Oh, and the Delta. 🙂



AMI S10430 Keyer / Divider chips.. And more..

This is a longish story, but I have now tracked down some NOS (New old-stock) AMI S10430 chips.

If you recall the original story, I needed one for my Korg Delta, but couldn’t find any. I then found a (REALLY COOL) guy in Holland who had FOUR untested chips. We did a deal, where I got one chip, and sold the other three for him (after testing). That worked out really well except for the stupidly long gap in the middle where I did absolutely naff-all. (Other projects, bah!)

Anyway, I found a link on a forum where another guy said he may have a couple of untested chips. I got in touch, and when he looked into it he actually had EIGHT, plus some other stuff. We’ve done a deal, and I bought the lot, untested.

I still have the Korg Delta with the socketed S10430 (IC3), so I CAN test them. I plan to keep some as spares, and sell some on. Depends on how many work..Watch this space. I MAY use eBay again, or just sell from this site.

I’m quite interested in the “other stuff” he’s bundling with the S10430s. These are described as “rhythm generators on a chip.”.  Again, watch this space..



[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..

Update: not any more. I did buy a new socket before they closed, though.

Still got issues with it. I think some solder traces are damaged. I have bought some new lead-based solder to try and fix this.

The dr-55 schematic suggests that pins 10,12,13 should be connected together, so a continuity test should confirm that.

Meantime, I “found” another (broken) dr-55 in storage.. More of the same..

[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, 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.