[sdiy] Non-DIY, but looking for repair advice...

[S Ridley]

If the output level is low, it may make pre-existing hum more noticeable,
so the two issues are not necessarily one fault.

Before opening it up, try to localise the fault:

- See if the output is hissy as well as hummy - that would suggest the
fault is further back and allowing VCF and/or VCA noise to be heard.

- Is it low level in all filter modes?  A dirty filter mode switch is a
possible cause of level drop.

- Turn up the VCA initial level - that would rule out a low envelope level
fault.

- Does an external signal and/or noise come through full level?  If so,
that would point to a VCO or buffer fault.

If the hum is removed by the filter, that suggests it's getting in before
the filter but after the source mixer..  There are two voice boards, with
the source mixer being the last thing on the VCO board and the filter the
first thing on the filter/VCA/EG board.  Faulty / dirty / oxidised
connections between the two board might be the problem..


Steve



Steve


On Mon, 13 May 2024 at 01:04, John Ames via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Slightly not-strictly-OT here, I s'pose, but I'm looking for hints/
> advice - I've got a Yamaha CS-5 that's mostly in good working order, but
> has two (possibly related) issues. One is that there's a slight 60 Hz
> buzz from the PSU - it's present even with the mixer sources turned
> off, but the filter can remove it. The other is that the output is very
> weak; running direct into my recording workstation, the maximum
> amplitude is lower than -30dB! Of course I could pre-amplify it...but
> then that boosts the AC hum from "not really audible" to "far too
> noticeable" :/
>
> Now, I haven't had it open yet; before I go poking around willy-nilly I
> thought I'd ask for any advice, and raise what may well be an important
> point. This is, or was, a Japanese import model, and the print on the
> back near the power cord lists it as a 100V device - but somewhere
> along the line someone covered that over with masking tape and Sharpied
> "115V" on it. I've never had problems running 100V equipment on US line
> voltages before, but admittedly it's almost all been digital gear; is
> that potentially an issue? And someone might have done a mod to adapt
> this thing for that already; any ideas what to look for if I open it up?
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