The Beat of a Different Drum

So it's time for the internet to whisper those four sweet words into my ear: For Parts or Repair.

This is the Roland TR-8 drum machine. It was, a few years ago, Roland's flagship drum machine, delivering accurate digital emulations of the classic TR-808, TR-909, TR-606, and with and extra upgrade the TR-707 and TR-727 drum machines.

This one, however, is feeling a little less flagship than it might have when it originally came out of the box, especially considering the layer of cat hair and grime it came coated in.

Well, the seller said that it suffered some water damage and wouldn't turn on, so let's have a look inside to see how bad things are.

Well those components are definitely covered in rust and corr- wait no, that's spider poop.

Ok, hang on, if I just plug this into my bench supply...

Right, yes. So the Roland TR-8 (and a few other boxes they made in this era) use a bit of a peculiar 5.7v center-negative barrel jack power supply. Most barrel jack power supplies are center-positive, and so if you try to plug into one of those due to, for example, misplacing the original power supply amongst a giant pile of cat hair and grime, then the reverse protection diode won't allow any current to flow backwards through the unit, and it will simply appear dead and unresponsive.

I guess I'll have less to fix on this unit than I initially expected, so let's get it cleaned up and put into service, starting with the spider poop.

Yup, that looks fine now.

The main panel PCB, upon a cursory examination, shows no signs of damage or spider poop.

Though it's certainly hosting its own collection of grime.

On both the faders and the potentiometers.

But it's easy enough to clean off. The pots just get a quick wipe with alcohol and a lint-free cloth, and the fader dust shields get cleaned by peeling the dust off using some scotch tape.

The case and knobs take a swim in some borax to strip off all the hand cheese and pet residue, and then things go back together as they came apart.

Except for one little problem. I was about to line up all the knobs to take a beauty shot when I realized that the knob for the snare drum compression effect wasn't turning.

Ah yes, there's the supposed water damage.

The rust on this pot here has managed to cake up inside the bushing and freeze the plastic shaft in place almost completely. These are just inexpensive 9mm pots, but I don't have spares on hand at the moment, so let's pop it out and see if it can be fixed.

And by "pop it out" I mean "struggle to desolder it for 10 whole minutes" since Roland didn't skimp on the thickness of the ground planes for this PCB, and all that copper was doing an impressive job of wicking the heat away from the lead-free solder. I did eventually manage to free it after diluting that higher temp solder with some classic leaded solder, but it took some doing. If I had to service more than one of these pots I'd probably invest in some Rose's metal to melt into the joints to really drop the melting temperature.

Anyway, it's out, so I just need to fold up the tabs on the bottom to disassemble it.

These will eventually fatigue and break off, but you'll get at least one folding cycle if you're careful, maybe two if you're lucky.

Once the tabs are folded up, the body of the pot can slide out of the frame and the shaft can be pushed out of the bushing (with some difficulty in this case).

And yup, there's some rust in there.

Luckily there isn't a ton, so filing away a bit of the buildup followed by cleaning out the rust grime is enough to get the shaft spinning freely.

And then, importantly, we add some friction grease to make the pot feel buttery smooth.

The reassembly is a little bit fiddly since the wiper is not solidly attached to the shaft, but placing it on the underside of the shaft (the right way up) and lining up the pins works well, and the body of the pot can be slid back on and the tabs re-crimped.

Then it's just a matter of soldering it back into place, with some nice shiny leaded solder. This is, thankfully, much easier than desoldering it.

Everything seems to be in good order now, so it can all go back together, for real this time.

And I can finally get that glam shot I was looking for.

Though I suppose I should probably get a proper power supply for it now.

But the important thing is that it works. Well, the important thing is that it's clean and it works.

And as a bonus, I verified that it does have the 707 and 727 models unlocked, which is sweet.