New MTG Kawai R100 ROM Switcher

As you may have seen in my previous post, my Kawai R-100 Drum Machine came with a 3-EPROM “soundswitcher”. Since this is no longer available, I thought I would make my own. It’s not an exact clone of the Drumware Inc board. First, I used different logic … just a personal choice. Second, I eliminated the ribbon cable to cut down on cost. It looks like there is just enough vertical room to pop the board on top, so that’s what I did. In my unit the Kawai ribbon cables are such a mess that it’s hard to close up the lid already. Finally I did a 2-layer board compared to the old Drumware single-layer board that was probably taped up by hand. In fact this is how I used to make SRAM  memory expansions myself in the late 80’s. I even advertised them in the back pages of Polyphony magazine (for JX3P, OB DX, Polysix and a few others).

Anyway, I have a couple of spare boards. They weren’t particularly cheap as I only had a few made, but if you want to buy a blank, let me know. They will probably be in the area of $50USD.  The other parts needed are sockets, round header pins, a 74HC138, two 4k7 or 10k resistors, some 0.1uF caps and one 10 to 100uF polarized cap. You also need the EPROMs and one SPDT 3-position on-off-on toggle switch. See the photos for more detail.

Kawai R100 ROM Switcher

Kawai R100 ROM Switcher


Kawai R100 EPROM Switcher Installed

Kawai R100 EPROM Switcher Installed


Kawai R-100 Drum Machine Front showing the switch

Kawai R-100 Drum Machine Front showing the switch

I also silk-screened the pin information on the top for people that are circuit-bending maniacs. This should give you a head-start locating bend points without trashing your existing hardware.

Read my previous post for more background info.


This entry was posted in Kawai R100 and tagged . Bookmark the permalink.

8 Responses to New MTG Kawai R100 ROM Switcher

  1. grantb4 says:

    By the way, I may make a kit at some point, but I don’t have all the parts gathered yet.

  2. Ron joseph says:

    I’d love a kit. I have 2 r100s.One has the expansion,one doesn’t. The expansion never worked fully, figured the EPROM was screwed.

  3. Jeff says:

    Dang! Just noticed the finished eBay auctions for these. Would love to get my hands on one. Any chance more will be available?

  4. grantb4 says:

    I have another blank board or two. I will build them up when I get a chance and post on eBay. I’m just getting caught up after the NAMM 2014 insanity.

  5. Hugh says:

    I’ll be putting my hand up for one of these too. Keeping an eye on the ebay, just missed the last one.

  6. grantb4 says:

    Sorry, … forgot to relist it. 😉

    BTW, contrary to my posts above, it is now a recurring item on eBay. Not just a one-off.

  7. Adrian says:

    Hi Was just wondering if you have any of these boards still avaliable?

  8. grantb4 says:

    I just sold my last one in the current batch yesterday. I will make more in the coming weeks.

Leave a Reply

Your email address will not be published. Required fields are marked *