My MS‑10 has been behaving a little poorly recently, with the EG release time fluctuating to a gradually growing degree. So I’m going to have a look at it. First, have a look at the service manual as this failure seems likely to be a misbehaving capacitor. And yes, there’s a 6µ8 Tantalum cap (C35) on the release stage, so that’s the main suspect. I hear some bad things about Tantalums, but I’ve never had one fail before. Anyhow, I did have the thing apart for cleaning when I got it but didn’t take the PCBs out as it involves a fair bit of unscrewing things. So this is my first look at the relevant board (KLM-126c).
(Picture taken after repair.)
Checking C35 in-circuit, difficult to be certain but nothing obvious wrong.
The SQ‑64 is a simple-looking but rather complicated digital sequencer which can receive and send CV/Gate/Trigger, Korg Sync, and MIDI signals, which is intrinsically a 64-step sequencer and which can chain sequences etc. It’s handy for translating analogue timing signals and setting up sequences for MIDI devices which can’t take a simple external clock, and so on. It has some limitations as a controller of analogue synthesisers however, but that’s not the topic today.
This SQ‑64 was I think bought new about two years ago, not long after they came out, and has developed a fault, so I’m going to investigate. The fault is that the eighth top row sequence button is activating intermittently without being pressed, which adds unintended gates to a sequence and prevents the user accessing additional functions in some modes because this button is interpreted as being pressed and having priority over other things, somehow.
I had occasion a few days ago to install MacOS 10.12 on an old laptop, and encountered an error message at what seemed to be the end of the process. Spent half an hour trying to see whether this was a known problem. It’s a little confusing because this was a fresh installation rather than an upgrade, and I found several references to failure messages in upgrades and ideas for how to fix the problem, as this was apparently quite common with 10.12, but not for new install.
Armed with a few very unlikely seeming ideas I restarted the machine intending to wipe the drive and start again . . . and then realised that the error message seemed to have come up at the point where the installer tried to load a message to say, we’re done for now and please restart to complete the installation. And it completed the installation. This took a while but it’s now up and running.
(I say it took a while but really it took far less time than it used to, swapping floppy disks in and out. It just seemed longer since there was nothing to do but watch.)
I managed to lay my hands on a secondhand Behringer 2600 ‘Gray Meanie’. I’ve never been fortunate enough to have a go on an original ARP . . . any original ARP . . . but from what I’ve seen and heard this seems to be sonically quite close to the original, but smaller, 19″ rackmountable, and even when new, significantly cheaper than any of the older or more recent clones of the ARP 2600. And it has some extra features. So they are perhaps becoming popular.
There are more reviews and videos of the different versions of this than I can count; so many that I’d never get time to play the thing if I watched them all. So I’m not going to cover the detail, just note a few things that come up and see how it works out.
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Once past the first hump or two of working out which things have to be turned up to make sounds, this synth seems to have lots of things waiting to be found. Still, after a couple of days with it, I’m a little disappointed to have not found more. Compared to other synths . . . but that doesn’t mean there’s no more there; it’s just how to get at it. In particular the Ring Mod is surprisingly uninteresting compared to others I’ve used; but maybe there’s more options I haven’t tried. The combination of the three VCOs synced is very interesting though. I also find that it’s capable of making some very nice bass tones which don’t reproduce well on small speakers. For which reason, this first sample video I’m doing is best listened to with good headphones or perhaps a PA.
The KM‑50 is a simple metronome made by Korg in around 1983–84. I have never seen one in real life, or photographs apart from catalogues from the period. And now this.
It’s a very basic device, simpler than the earlier Korg RT‑10, consisting of a timing pulse with a higher-frequency sound as a bar pulse. It also has a needle timing indicator like a miniature physical metronome. The timing range is set with a rotary switch, from 40 to 208bpm. The bar pulse can be from 2/4 to 6/4 or off. And it has a tuning pitch, which varies from an unusual 439 to 444Hz, the frequency set with the same linear switch as the bar pulse. The frequency is pretty accurate but wavers very slightly. It takes 9V DC external power or can be powered by a battery. (Unusually for products of this age it seems to work quite well with a rechargeable battery.)
Like many other metronomes, the sound it makes from its built-in speaker is quite irritating and I doubt I would be able to focus on music with that going on. Unfortunately, while the sound can operate without the needle, the sound can’t be switched off separately, unless a cable is plugged into its signal output. It has a 3·5mm TS jack for this, and this rather more interesting. Checked on the oscilloscope, the normal signal is a +8V rectangular pulse which fades out slightly at the end. The bar pulse seems to go through a resonant filter.
I won’t be using this as a metronome in the ordinary sense, but a stepped +8V pulse generator means a timing source that could be run into one or more synth clock inputs, with appropriate attenuation and/or inversion, and even though this seems extremely rare in the secondhand market, it was cheaper than the majority of simple Eurorack timing clocks I’ve seen. I don’t have any specific plans at the moment but it’ll probably be useful at some point.
Posted under Musical Technology at . Last updated 2024-01-15 19:15.
The Stringvox (without a space) is Hohner’s rebadging of the ELEX K2 electronic piano/string machine. There were three versions sold by Hohner, the original ‘silvertop’ (K2r1 by my nomenclature) which seems to have begun production in 1975, the slightly changed rev.2, and the ‘blacktop’ (K2r3) from 1979. All are in effect built into their own flightcases with lift-off lids, but the r3 case shape is different. (For more information on the series see A Spotter’s Guide to HIPs and Strings.)
I have only been able to find out a little about these previously; in particular I have little information about the interior. [1] Recently an r3 came up for repair, so let’s have a look.
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This Stringvox (K2r3)
This was sold as in need of repair, with the main known problem being that the plug side of the appliance fuseholder is missing. [IN1] Other than that, it came with a stand but without its case-attachment bolts. [IN2] (This is one of those instruments which can rotate on its stand to get a better playing angle, though the stand doesn’t adjust vertically so that’s of limited use.) It could of course do with a clean up and maybe some repair of the vinyl. [IN3] There’s a bit of rust on the hinges. [IN4] As is quite common with these keyboards, the plastic edging on the ports hole on the rear is incomplete. (This is what you get when you put the ports on the outside of the flightcase.) [IN5] It hasn’t been used for some time, perhaps several years, so given its age we can expect some capacitor issues. [IN6] However, under the cover it’s in better condition than most I’ve seen. It would originally have come with sustain and volume pedals and a music stand but these have all gone. It has a socket for a bass pedal board but they were optional extras, and since I’ve never seen Hohner or ELEX bass pedals, they probably weren’t popular.
Condition
On arrival . . . it’s heavy! This is certainly the heaviest single-manual keyboard I’ve ever handled. Its lid is slightly misplaced as if something has bent but we’ll see. Some of the keys have slight dents and scratches but they all operate well and the bushes don’t seem to have hardened. This one originally had two bass-range marker tabs but one has gone. [IN7: Consider missing tab replacement.] There’s a vaguely mushroomy smell, but I understand this has been sitting doing nothing for about ten years so not surprising. The switches all operate without too much stickiness and only two of the faders are a little sticky. [IN8: Clean faders.] There’s a power cable under the lid (nice plug, 5A cable, 13A fuse . . . replaced with 5A for now), and what looks like part of the handle in the packaging. I reattached that before going any further. I can’t do much else without replacing the fuseholder, so time to get it open.
