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Siel DK-600

A very interesting synth. It’s one of the first (or last) “original” analog synths with both MIDI and complete knobs-and-switches controls.

As received:

No backup battery installed
Missing most screws
One broken key & one key missing
Missing left end panel
Several broken plastic pieces
Adhesive goo all over panel
Bottom case full of mouse poo

It did power up, though, and made sounds when poked at.

Despite the odd end panels, it’s one of the easiest synths to work on I’ve run across. There are acres of open space, all the cables are nicely run, and everything is labeled. The one downside is the odd shape, which made fabricating replacement end panels a bit of a challenge.

When I removed the main board, under the keybed assembly, I got completely squicked out when I realized the case was full of mouse droppings. Although that was fairly gross, the other thing I found were bits and pieces of the foil wrapper from a chocolate coin. Which may have been rodent food, but since foil is (obviously) conductive it was also a disaster waiting to happen. I’ve gotten some pretty filthy hardware in the past, but this is the first one I’ve ever had to hit with Lysol.

At this point, locating replacement keys isn’t much of a problem. I have several sources, and apart from the fact that one is a slightly different color and is missing a bit of the front apron, they went in without a problem. The velocity-sensitive key triggering mechanism is unusual. In most of the other synths I’ve seen, each key has two contacts, one set slightly in front of the other. When a key is struck, the time difference between the two contacts is converted into velocity information. Here, instead of individual contacts a pair of buss bars is used, and the interval measured is the time between breaking contact with one and connecting to the other.

The missing backup battery was easy to identify – there was a screened sqare labeled “backup battery” on the main bord, with the terminals clearly indicated. After removing the old solder and broken terminals, I tried to find the most sutiable replacement. My first choice is always a standard CR2032 socket. The pin spacing was correct, but there were a couple of resistors and a disk capacitor in the way. Thought of just mounting it on the bottom of the board, but the plastic bottom case has a reinforcing rib running exactly where it would have ended up. With a little creative lead-bending, I was able to mount a 1/3 AA socket on the top.

Downloading the factory patches was a challenge. I was able to locate a WAV file, but spent more than an hour trying to match volume levels to get a clean restore, with no success. Finally, after much web searching, I found a SysEx dump that I was able to reload using MIDI-OX. Somewhere I also dug up the original patch list. The synth came with the patch list on a label stuck to the front panel – hence the paint chips – and I laid out the new list to match the original as closely as I could.

The patches loaded correctly, and everything sounded okay. The odd numbers on the keypad, however didn’t work. I was able to determine that one of the pins on the DIP-style connector on the ribbon cable was missing. These are readily available, but rather than wait until the next time I order from Mouser I rigged a small piece of metal in the socket so that it would contact the little stump of the missing pin. It works fine.

I’d iniitally intended to make very nice end panels, but because of the odd shape decided that a basic set would do, particullary if I was reselling the unit.So instead of oak, I used clear pine, and instead of mounting them on the outside of the case and filling in with more wood, I mounted them on the lip next to the edge instead. After filling in the original screw holes and painting the lip black, it looks fine.

One of the nifty things I didn’t realize until I’d actually finished working on it is that it has a set of fold-down legs to angle the unit upwards, making the control panel easier to access when standing. Kind of neat.

Determinng the value of something like this is always tricky. I’ve seen them sell for close to $800 on Ebay. However, I’d rather trim my nails in a Cuisinart than go through the hassle of trying to sell something this large and this vintage-y that way. I’ve done my time. Instead, I posted it on craigslist with a low yet still fair price. It sold within  a couple of days; the buyer was very happy, I got some hassle-free cash, and it went to a good home. Everybody wins!


The Kurzweil K1000 – Welcome Home!

In 1987 when IBM introduced their new PS/2 computer lineup, mixed in with all the fancy new machines was a nondescript add-on card called the IBM PC Music Feature. Retailing for  about $495, it was essentially  Yamaha’s 4-operator  FB-01 FM synthesizer on a card, coupled with a MIDI interface.  Around this time I was working as a hardware tech in a computer store in New Jersey.  They had actually had a system set up with the Music Feature, a Yamaha YPR-9 piano, and whatever the heck the software was that ran the card (I know it WASN’T Play/Rec; beyond that I don’t have a clue).

Since I’ve been interested in electronic music forever, and since no one else in the store had a clue what to do with it, I talked the owner into letting me take the system home occasionally. So when they finally had someone who was interested in purchasing a complete setup, naturally they had me do the demo.  Those were the days…they sold a $3500 computer with a $500 sound card, based on my dubious selling skills and a badly programmed version of the Miami Vice theme.  I did cheat, a little – in addition to the computer, I also had a Casio CZ-101 doing the guitar parts.  Not that anyone noticed, of course.

The customer wanted a really good keyboard – he didn’t like the dinky piano we were using (well, neither did I).  Given a (literal) blank check, I went to Sam Ash in Edison and picked out the Kurzweil K1000 as a controller.  If I could never actually own one, at least I could visit with it for a while.

And visit I did – I loved it. Loved the keyboard action, loved the look, and loved the sounds. As I recall I sold at least two other complete systems, and each time the K1000 was carefully and thoroughly tested for as long as I could possibly justify it.

Flash forward to, well, now. Although the K2000 series and beyond are firmly established as classic high-end high-power machines, the K1000 series faded quickly. They would show up on Ebay from time to time, usually for a couple of hundred dollars but always with outrageously high shipping. Which only makes sense as they’re made of things like real metal and weigh a ton. But I read craigslist… a lot. And about twelve seconds after one was listed a few weeks ago, I got it.

I have an absolute limit of $100 on any single piece of kit. Although I have a lot of equipment, my cheap nature (or thriftiness) means that most of the things I buy have something wrong with them. But in this case, I got the K1000, the stand, both original pedals, a copy of the manual, and the power cord, for that same $100. The only defect at all – which I didn’t even notice until I was reading up on the unit – was the backlight was bad.

Although it’s not really a big deal, my eyes aren’t all that great anymore.  There are a number of approaches to this, but since I found a guy on Ebay selling replacement EL panels for $25, I went the easy route.

Working on this is a dream. It’s big, well-made, solid, and logical.


From left to right, the processor board, the keyboard logic board, and the power supply. There is a lithium backup battery, but it’s very intelligently mounted on the power supply PCB instead of, say, the middle of the programmer board (yes, Korg, I’m looking at you).

This is the panel board which contains the LCD display.


Sorry about the odd colors – it’s a new camera & I haven’t figured out all the settings yet. Here’s the actual LCD panel with the LCD removed from the circuit board and the EL panel visible, and the replacement EL panel. I used flush cutters to snip the two leads on the existing panel, tinned the little copper tabs on the replacement, and soldered it in as quickly as I could to avoid melting the covering.


This is the panel after the install. Which you could see in the first picture  if the flash hadn’t gone off. You may also notice the display looks a little odd – I initially installed the LCD upside down, which offset the element contacts and shifted the letters over one row.  Memo to self – magic markers are our friends.

I also took the opportunity to clean the inside and out, checked all the connections, made sure the backup battery was holding a charge, and tested all keys, all switches,  and the pitch & mod wheels.  There are no other problems.

And it still sounds awesome.