Vintage Synth Repair

Hi guys,

I have a fault on my Korg Delta. Since opening her up to replace a couple of broken keys (with thanks to Dave Garfield..!)... but, I have now got a strange 'hum' when a key is pressed. The 'hum' is low frequency and the same on all keys (seems to be in tune with the low G) As it is on both string and synth sections I suspected the main board where the oscillator is, as all functions - filter, chorus, envelopes seem to affect it. Indeed, today whilst messing/poking around the osc section it seemed to fix itself - then reappeared! 

There are no dry joints so I suspect component failure.

I have changed most of the caps around the oscillator but am not sure on the value of a few.

I have downloaded a free schematic but looking up close at the main
board cct diagram, it is really a bad copy and doesn't tell me the component values.

Would anyone here have a good copy or at least a copy of the schematic of the keying and oscillator board KLM238(a) circuit please.

Many thanks
TOM

I'm not familiar with the Delta, but based on experience with other machines, I'd be looking for a grounding fault, too. Sounds like you disturbed something while working on it.

--- In vintagesynthrepair@yahoogroups.com, Tom Russell <russelltc@...> wrote:

>
> Sounds to me that a ground connection was lifted- at least intermittently.
>