Rebuilding a Roland KD-8

So I walk into the local drum shop and I see a used Roland KD-8 at a rock-bottom price. "My lucky day," I thought to myself.

Upon closer inspection (and as you can see from the photo you didn't have to get that close) I saw a couple of round scars on the rubber head. They almost look melted. A drumsmith who was in the shop at the time commented that some glues can do that to rubber and it might be from a kick-drum patch.

I plugged it in to a Roland TD-3 module and it triggered so faintly as to be almost unusable. Pressing on the head also yielded no resistence, like the inner foam was gone. They dropped another $25 off the price and I took it home for "parts."
Scarred KD-8
The first thing I did was take the KD-8 apart. The inside of the rubber head was smooth so the scarring was only on the outside.
The trigger is a layered sandwhich of components. First there is a soft rubber disk, then a layer of foam, then a metal plate with a piezo on the back, then another layer foam shaped like a donut and finally, the steel body of the KD-8.

The two foam disks were essentially hollow. Almost a powder. I don't know what caused it, but all I needed to restore this baby was two new foam disks.

The hard part was to removed what was left of the foam from the other pieces. This took me about two hours of peeling, scraping and fingernail polish remover-ing.

The foam used was a little softer than I normally use, but luckily I had some in my pile of junk and scraps. My foam was 1" thick. The foam used by roland was 1 cm. 1" is a little more than 2 cm, so I cut out a disk and sliced it in half with my hot wire cutter. I glued it all together with silcone rubber glue and the result is on the right.
After letting the smelly glue dry (and silcone rubber glue sure does smell) I replaced the outer rubber head. No problems.
Here is the repaired KD-8, fully repaired. I immediately took it down to the Mondor and tested it out. It is not as sensitive as my factory KD-8, but it was easily compensated for by adjusting the pad sensitivity up 3 notches. Nowhere near as bad as before the rebuild. I am going to assume this is due to the foam I used with was slightly less dense than the Roland foam. Bottom line is that I have a nice functional KD-8 at a price that would make you cry.
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