[sdiy] 808 help

[jhno]

>I've got a TR-808 with a sketchy tune control on the Low Tom.  It
>works, but when it get's to the lower range, the pitch can go high,
>especially with a little downward pressure on the resistor.

it took me a while to realize: you mean VARIABLE resistor, aka
potentiometer (or rheostat, depending on how it is used).

before you go about replacing the pot, which is non-trivial, you should
attempt to clean it. the least invasive step would be to use compressed air
in an attempt to dislodge contaminants. if this is ineffective (which seems
likely), personally i would spray some caig de-oxit (once known as cramolin
red) inside it and see what happens. some people seem to recoil in horror
at the use of such chemicals - but i don't know why. it should only be used
in appropriate circumstances, but i have had great results using it to
clean old potentiometers. DO NOT USE on conductive plastic devices, such as
high end mixer faders.

opening up the 808, removing the main board, de-soldering the pot, and
installing a new one comprises a lengthy operation with numerous
opportunities to screw up other aspects of the machine. even the
modifications usually done to add additional control over the sounds do not
require removing the main board. it is a complex machine, and when the
inside is exposed it is quite fragile.

incidentally, i heartily recommend some of the mods for expanded tonal
control. i installed the analog solutions mod kit in my 808, which made it
a much more flexible synth. here is a page of mods for different synths and
drum machines offered by A.S.:
http://www.users.globalnet.co.uk/~concuss/mods.htm

jhno


ps - you can swap knobs on the potentiometers however you like. i recommend
exchanging knobs among your equipment when it results in a more pleasing
presentation.