Yamaha CS80

On Thursday, June 11, 2015, Tim Conniff tconno@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

 

Hi Bob

 You bought a part from me a while back....

80% chance there's nothing wrong with the supply at all. 

I assume you've thoroughly investigated visual possibilities on the 2 offending voice cards, but

it's highly likely everything funky resides there.

 You MIGHT want to swap the location of a working card with one of the 2 bad ones, and see if the problem moves, because it could also be something external but related to that voice(s) giving this

 headache.  Probably 45 minutes of soldering/desoldering to verify. God knows the wiring can create nightmares on these....but at least you'd know more than you do now about the prob.

good luck

Tim

On Thursday, June 11, 2015 8:58 AM, "bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

 

OK... so I'm going to build a power soak to try and pin this down. ie. whether it is actually the PSU or if it's something elsewhere causing the issue.

Measuring about 0.6A on the +15V, and 0.65A on the -15V... Does that sound about right?

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.

 

Stephen

 

Gesendet: Donnerstag, 11. Juni 2015 um 17:06 Uhr
Von: "bob@... [yamahacs80]" <yamahacs80@yahoogroups.com>
An: yamahacs80@yahoogroups.com
Betreff: [yamahacs80] HIgh Pitched Whine

 

Hi


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

On Saturday, 9 January 2016, 'Stephen Parsick' wavecomputer360@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

 

A while ago there was a report on a German synth collector/musician in KEYBOARDS magazine in which he described this problem. He had some decoupling capacitors replaced which fixed the problem -- maybe someone could look up more accurate details?

 

Stephen 

 

Gesendet: Samstag, 09. Januar 2016 um 18:18 Uhr
Von: "fanwander@... [yamahacs80]" <yamahacs80@yahoogroups.com>
An: yamahacs80@yahoogroups.com
Betreff: Re: [yamahacs80] HIgh Pitched Whine

 

Did you succeed fixing this 5kHz whining?

On Sunday, 10 January 2016, 'Stephen Parsick' wavecomputer360@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

 

Don't take my word for it, I can only vaguely remember what was written in the interview. I seem to remember that it had something to do with the illuminated push buttons as well.

 

Maybe some other German-speaking member of this group has the issue at hand?

 

Stephen

 

Gesendet: Sonntag, 10. Januar 2016 um 07:55 Uhr
Von: "Bob Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com>
An: "yamahacs80@yahoogroups.com" <yamahacs80@yahoogroups.com>
Betreff: Re: [yamahacs80] HIgh Pitched Whine

 

Not had the time to investigatefor a while, but am aiming to get stuck in again next month.

Reckon the fitst thing to do is look at decoupling caps.

Bane of my life this CS ;-)

 

B 

On Saturday, 9 January 2016, 'Stephen Parsick' wavecomputer360@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

 

 

A while ago there was a report on a German synth collector/musician in KEYBOARDS magazine in which he described this problem. He had some decoupling capacitors replaced which fixed the problem -- maybe someone could look up more accurate details?

 

Stephen 

 

Gesendet: Samstag, 09. Januar 2016 um 18:18 Uhr
Von: "fanwander@... [yamahacs80]" <yamahacs80@yahoogroups.com>
An: yamahacs80@yahoogroups.com
Betreff: Re: [yamahacs80] HIgh Pitched Whine

 

Did you succeed fixing this 5kHz whining?