On Thursday, June 11, 2015, 'Stephen Parsick' wavecomputer360@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:
I recently read about a modification that was done by Kent Spong which involved re-routing the cable loom because it would produce some kind of high-pitched whine. Maybe Kent could elaborate on his?Mine does that as well but it's only audible when playing lower notes.StephenGesendet: Donnerstag, 11. Juni 2015 um 17:06 Uhr
Von: "bob@... [yamahacs80]" <yamahacs80@yahoogroups.com>
An: yamahacs80@yahoogroups.com
Betreff: [yamahacs80] HIgh Pitched WhineHi
Still having issues with this CS50 PSU.
I've got a horrible high pitched whine all over everything. If I turn the amps off, I can actually hear this noise emanating from the PSU.
If I put a probe on the lines, I've got oscillation on both the + and -15V lines. Much worse on the -15V line.
I've recapped it, changed all the transistors, and diodes (Apart from the rectifiers)
Changed the 4458, but no change.
What's really odd is that if I touch the anode of the -15V zener (Opamp supply) with a scope probe, it collapses the Opamp supply.
Also... If I remove voice cards 3 and 4 from the rack and the problem goes away... even though they're still connected to the power.
Any incite, or suggestions most welcome... I've got to get this thing sorted in a couple of weeks, so a client can use it on a session. :-s