General thoughts for component replacement in cheap 1980's organs?

[Woody Bergman]

The specifics:
I found a Kawai DX 80 (1982?). The board that controls the "Electro Chord Bass III" looks like something was spilled on it, but the rest of the organ is in great condition. I have to replace a 0.47 uF 50 volt electrolytic going between the Electro-Chord volume and the ground, as well as that volume slider and a bunch of small signal diodes. I tinkered with electronics decades ago, and remember the how, but not the why, so...

The 3 general questions:
1.) While I'm at it, should I replace other capacitors with something more durable or audiophile-friendly?
I don't want to have to open this up again anytime soon, and am willing to spend extra money on parts.

2.) Is any distortion or normally undesirable effect of electrolytic caps a critical part of the sound generation, or does it just come across as noise?
I want this to sound like what it is, but without a punishing degree of authenticity. Nobody's ever going to complain that this isn't a genuine DX 80 sound.

3.) Do you have any general recommendations on which parts of the circuit to upgrade and which to leave alone?

If you have any opinions on any of these 3 items, I would really appreciate your input. Thanks in advance!

[davidecasteel]

I'm not an expert, but I've read many times that electrolytic capacitors are subject to failing over time. It might be wise to replace any of those you see.

David

[Admin]

Personally, I subscribe to the "If it ain't broke, don't fix it" school of repair, but if you don't want to have open the organ up again, replacing all the electrolytic capacitors in the organ should be considered. The ones in the power supply are probably most the important.

Golden eared audiophiles will tell you that electrolytics in the signal path have a terrible effect on the sound, but I'm of the opinion that the effect is negligible and inaudible to most, and not worth the effort to change.

[Woody Bergman]

Thank you, David and... uh... Admin! So here was my thinking. If I was making a circuit to amplify an existing sound, without changing the sound, this would be an obvious choice: Use the cleanest-sounding capacitors possible. My hesitation was that we're creating sounds from scratch, and that requires some scratchiness. No guitarist would want a Marshall stack if it didn't distort their sound. At the same time, they wouldn't want to hear a 60 Hz hum coming from that stack. I may end up replacing all the electrolytic caps with new electrolytic caps, or swapping out the ones in the power supply with a better quality type, if I can find one (Good suggestion, thanks!). Not sure at this point.

One of the things I want to do with this organ is create a sample bank to preserve the organ after the other parts fail, and so I don't have to keep this big thing in my apartment forever, so I'm now realizing that whatever I put in will last long enough, probably long enough that other components will fail first.

I'll post on the forum when I have that sound bank available. It will probably be a few years, since I have little spare time and no recording space big enough for the organ, right now.

[Woody Bergman]

In case anybody is trying to find the small switching diodes Kawai used (with the yellow band), it appears to have been an obsolete ROHM 1SS133T-77. I don't really know what I'm doing, but I'm going to try a Vishay 1N914TAP as a substitute. I'll let you know if anything blows up, unless anybody knows of a better replacement?

After taking the rest of the organ apart, I decided not to replace the hundreds of capacitors I found. That would take forever. It so happens that ELNA still makes the same exact electrolytic caps, so I'm just getting a few of those to replace any suspects. I'm guessing the volume slider was a 50 ohm like the others, so I'm hopefully going to shoehorn-in an Alpha RA3043F-20-10EB1-A50K.

I'm getting this from Mouser because they have a nice search function. Last time I ordered from them was in the 1990's. Wow.

Wish me luck!