Odyssey filter repair

[Matt Haines]

>     I've had two "dead filter" Odysseys. One had a potted VCF (sealed) so
>     I replaced it with the VCF from my stupid piece of crap spare parts
>     Omni, and the other was open to the world so I replaced the LM3900 and
>     it was good as new.
>
>     If you have a truly dead VCF and it's potted, I'd give the following
>     advice:
>


It's not potted, and I've got a spare 3900 so that's one of the things I'm
going to try first. Joachim has been very helpful in suggesting ideas so
far, and I appreciate your input as well!

>     I remember fixing a VCO - it was the 4011 CMOS NAND gate. Can't
>     remember if it was "A" series or "B" series CMOS, or if it mattered
>     (Joachim, are you reading this?).

Another useful thing to check. Luckily, I've got a fully-working Odyssey as
well, so I can check between the two to see where inconsistancies lie.

>
>     Sliders can be found at surplus shops. Watch out, there's 100K and 1M
>     and it does make a difference in the envelope generators for example.
>     I think I've had to compromise and use linear taper rather than audio,
>     but that never bothers me.
>
>     Keep at it! Even if you gut the thing you can still use the keyboard
>     and the case maybe for a DIY project. Most of the hassle with a DIY
>     synth is the enclosure and panel. The Odyssey is a very cool machine,
>     very ergonomic IMHO. The patching method of parallel input attenuators
>     on each module, with a source select switch, is really ingenious and
>     one of the reasons that the Odyssey is equally at home making musical
>     sounds or spaceship noises. I have an old schematic and on it an old
>     electronics buddy of mine wrote these prophetic words:
>

The keyboard will be going in my working Odyssey, because the working one
looks like it needs dental work (the pads are shot and the keys are uneven
and clanky). The broken Ody, ironically enough, has a nice keyboard and a
working PS.

As for sliders, I'm not fond of the way they get crappy. My Sh101 and my
working Odyssey both have had to have sliders replaced. Also, the Odyssey
sliders are a bit stiff for my tastes. So a-rackmounting I will go,
replacing all the sliders with pots. I'll probably split the Odyssey (the
dead one) into a dual-VCO+LFO module, and another with the VCF/EG/VCA
boards (or ignore the VCA or whatever).

>     "The Odyssey is one of the best-designed synthesizers on the market,
>     both from an engineering and a musician's point of view. It merits
>     close study."

In my uninformed opinion, it *is* laid out very well. Looks much more
primitive than say the later Roland stuff, but that's to be expected. Pins
have numbers, diodes have etched traces to mark their position on the other
side, etc. Thoughtful indeed.


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