Date: Fri, 25 Oct 1996 11:42:03 -0700 (PDT)
From: The sloth <n9446600@cc.wwu.edu>
To: wavestation@cloudfactory.org
Subject: [WS] a foray into the guts of an EX
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Considering that American Music wants $60 an hour to fix a Wavestation, Korg wants $170 for a Power Supply board and $20 for a shop manual, and I'd have to wait two weeks for any of this anyway, I got adventurous last night and opened up my EX. Here's a few observations and discoveries:

Getting inside the WS is really really easy. It took me 5 minutes and a phillips head screwdriver.

Getting the PS board out is almost as easy; It did, however, involve a pocketknife and a pair of needlenose in addition to the phillips, though...;-)

The battery is right there, and it looks pretty standard. Next time I go digging, I'll write down what it is and see if it's available from a source other than Korg. I didn't think of it at the time.

The I/O board (midi and audio) appears to be the same as the M1's. Is this true?

The Keybed itself is a Yamaha action, and it's beautiful.

Wherever they put the dreaded lithium grease, though, isn't immediately accessable. I don't think it would take too much more digging, though.

To answer my own question: yep, the mod wheels are ridiculously easy to attack. They're right there.

The main CPU is a Hitachi of some number I didn't recognize; I was expecting a slow Motorola 68K or maybe even an Intel. Does anyone know anything specifically about the main processor? Just curious... [ed. note: Joe Brian has provided an answer to this question. -S.C.]

Notes specifically regarding the Power Supply board:

It doesn't seem so much designed as "fitted." There are two tiny little transformers, a bridge rectifier, a full wave rectifier, and an untraceable wad of capacitors. Seems that the filtering on the power was sort of hit or miss... I can't say that I'm impressed with the design, and I'm not really surprised that they fail a lot.

There are few concessions to heat dissipation on the board: one 6.8 ohm ballast resistor, and a handful of high heat capacity resistors; no thermocouples or heatsinks to be seen. There's also (understandably) nothing on the board more complicated than a diode, and nothing more expensive than a buck, near as I can tell. I consider it a real disservice on Korg's part to replace BOARDS ONLY as I can't imagine the entire subcircuit failing as a whole instead of a few overworked components quitting (I still suspect that ballast resistor, but it passed both a continuity and a sniff test).

If the Wavestation were a microwave and you brought it in to a repair shop to get that circuit fixed, you'd probably be looking at 5 bucks in parts and maybe 20 bucks in labor; total time in, board out and in, and zipping the thing back up was under 20 minutes (I subtracted my circuit analysis and general reconnoissance time from that). I'm definitely getting a shop manual and fixing the thing myself. The guy I bought it from paid a mechanic $379 to do the job (and he failed).

Here's the curious bit: once I had the board out, checked it all for continuity and "smell", gave it a go and put it back in, the WS worked like a charm!! I left it on all night (burn in test) and it went 12 solid hours before it started playing the hard reset game with me, and even now it's doing it a lot less. This leads me to believe that my fault is somewhere between the PS and the CPU, but I'm not sure. I don't think it's the PS board, but I'm humoring the theory that when that ballast resistor heats up, the resistance goes too low, it shuts down the Zener diodes, the power supply quits, and the thing resets... but that's just a crackpot theory for now.

I forget who on this list was on the original design (but you have my kudos and worship) but if they had anything to do with the power supply or if they know anything about it, could you share a little wisdom with me? What is it on there that actually fails most of the time?

If you people don't want to hear this kind of stuff, tell me and I'll shut up next time. I just thought it might be of general interest.

<(*)>sloth<(*)>

As a side note, I also discovered with joy how much simpler Wavesequences are to program when you have a gigantic display and a numeric keypad, compared to a 2x16 and + and - buttons...;-) YAY!!