Yamaha CS80

are all 3 fuses intact?

---- On Thu, 17 Jul 2014 11:14:08 -0500 bob@... [yamahacs80]<yamahacs80@yahoogroups.com> wrote ----

Hi


Just servicing a CS50, and it's constantly outputting a whine of about 4120Hz.

Unit came to me a bit battered as the PSU had shaken loose and trashed a few things inside.
PSU PCB had become cracked, so replaced that with a working one purchased from Synthparts.
Recapped the new PCB before I fitted it.

I've done the usual, changed the logic on the KAS board and the S/H board, replaced power decoupling caps throughout etc.

The only difference is that originally it took a minute or so to manifest... now it manifests immediately.

I can see the signal on all power lines.


Any thoughts?


B

Can you remove the supply, give it all needed dummy loads, and or short sense lines to their respective power lines? Then you can determine if it is strictly from the supply, or a function of the load inducing a resonant freq, or other anomaly. I assume you have a scope.

Tim

On Thursday, July 17, 2014 11:04 PM, "Bob Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Only two fuses on the CS50.

Voltages are all there, but there's this signal sitting on top of them.

Synth works fine other than the whine, and a duff LFO chip.

Thinking it's got to be a duff semiconductor/ IC on the PSU :-(

B

On Friday, July 18, 2014, laurie laurie@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

are all 3 fuses intact?

---- On Thu, 17 Jul 2014 11:14:08 -0500 bob@blzproductions.com [yamahacs80]<yamahacs80@yahoogroups.com> wrote ----

Hi


Just servicing a CS50, and it's constantly outputting a whine of about 4120Hz.

Unit came to me a bit battered as the PSU had shaken loose and trashed a few things inside.
PSU PCB had become cracked, so replaced that with a working one purchased from Synthparts.
Recapped the new PCB before I fitted it.

I've done the usual, changed the logic on the KAS board and the S/H board, replaced power decoupling caps throughout etc.

The only difference is that originally it took a minute or so to manifest... now it manifests immediately.

I can see the signal on all power lines.


Any thoughts?


B

dummy load may become pivotal in determining the source of the issue.

Alternatively, of course, you could substitute another source of power if available, and i don't mean another cs50 supply, I mean ANY other capable source.

Given the whine's prevalence on the power lines, you might also want to disconnect the juice to the voice cards all at once and see if it's still being heard, just to further rule out stuff.

Btw, I have found a 150, just haven't had time to check it yet.

good luck

Tim

On Thursday, July 17, 2014 11:38 PM, "Bob Stewart bob@blzproductions.com [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

I don't have a dummy load unfortunatley, but did short the sense lines and look at it.

Seemed to be OK, but might need to run it for a while to let it warm up first.

Might just be that something's beginning to fail under load. Just really annoying that it's showing up on all the power lines. Might have a chance to look at it further today, but have a MonoPoly to tune, and a Prophet 5 to diagnose over at a clients.

On Friday, July 18, 2014, Tim Conniff tconno@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

Can you remove the supply, give it all needed dummy loads, and or short sense lines to their respective power lines? Then you can determine if it is strictly from the supply, or a function of the load inducing a resonant freq, or other anomaly. I assume you have a scope.

Tim

On Thursday, July 17, 2014 11:04 PM, "Bob Stewart bob@blzproductions.com [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Only two fuses on the CS50.

Voltages are all there, but there's this signal sitting on top of them.

Synth works fine other than the whine, and a duff LFO chip.

Thinking it9;s got to be a duff semiconductor/ IC on the PSU :-(

B

On Friday, July 18, 2014, laurie laurie@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

are all 3 fuses intact?

---- On Thu, 17 Jul 2014 11:14:08 -0500 bob@... [yamahacs80]<yamahacs80@...m> wrote ----

Hi


Just servicing a CS50, and it's constantly outputting a whine of about 4120Hz.

Unit came to me a bit battered as the PSU had shaken loose and trashed a few things inside.
PSU PCB had become cracked, so replaced that with a working one purchased from Synthparts.
Recapped the new PCB before I fitted it.

I've done the usual, changed the logic on the KAS board and the S/H board, replaced power decoupling caps throughout etc.

The only difference is that originally it took a minute or so to manifest... now it manifests immediately.

I can see the signal on all power lines.


Any thoughts?


B

made a blunder, supply currents won't be different at DC, only AC area.

Time to get sleep, apparently.

T

On Friday, July 18, 2014 1:01 AM, "Tim Conniff tconno@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

I haven't worked on a 50 in 5 yrs, but I believe the US model draws

around .3A on the 15's, and slightly less on the 8.5/6.5 lines.

for test purpose you could get by with that.

In the UK, should approach half that, in theory. (for what that's worth):)

Tim

On Friday, July 18, 2014 12:36 AM, "Bob Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Yeah, disconnecting stuff was going to be my next thing.

I do have another CS50 , but the PSU has been modded and the connections are different. Otherwise that would've been the quickest solution.

Will check out what I need for dummy loads as well. Not sure what the current consumption is on the different lines.

Keep me posted about the 150

Cheers

Bob

On Friday, July 18, 2014, Tim Conniff tconno@sbcglobal.net [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

dummy load may become pivotal in determining the source of the issue.

Alternatively, of course, you could substitute another source of power if available, and i don't mean another cs50 supply, I mean ANY other capable source.

Given the whine's prevalence on the power lines, you might also want to disconnect the juice to the voice cards all at once and see if it's still being heard, just to further rule out stuff.

Btw, I have found a 150, just haven';t had time to check it yet.

good luck

Tim

On Thursday, July 17, 2014 11:38 PM, "Bob Stewart bob@blzproductions.com [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

I don't have a dummy load unfortunatley, but did short the sense lines and look at it.

Seemed to be OK, but might need to run it for a while to let it warm up first.

Might just be that something's beginning to fail under load. Just really annoying that it's showing up on all the power lines. Might have a chance to look at it further today, but have a MonoPoly to tune, and a Prophet 5 to diagnose over at a clients.

On Friday, July 18, 2014, Tim Conniff tconno@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

Can you remove the supply, give it all needed dummy loads, and or short sense lines to their respective power lines? Then you can determine if it is strictly from the supply, or a function of the load inducing a resonant freq, or other anomaly. I assume you have a scope.

Tim

On Thursday, July 17, 2014 11:04 PM, "Bob Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Only two fuses on the CS50.

Voltages are all there, but there's this signal sitting on top of them.

Synth works fine other than the whine, and a duff LFO chip.

Thinking it's got to be a duff semiconductor/ IC on the PSU :-(

B

On Friday, July 18, 2014, laurie laurie@ronchmusic.com [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

are all 3 fuses intact?

---- On Thu, 17 Jul 2014 11:14:08 -0500 bob@blzproductions.com [yamahacs80]<yamahacs80@yahoogroups.com> wrote ----

Hi


Just servicing a CS50, and it's constantly outputting a whine of about 4120Hz.

Unit came to me a bit battered as the PSU had shaken loose and trashed a few things inside.
PSU PCB had become cracked, so replaced that with a working one purchased from Synthparts.
Recapped the new PCB before I fitted it.

I've done the usual, changed the logic on the KAS board and the S/H board, replaced power decoupling caps throughout etc.

The only difference is that originally it took a minute or so to manifest... now it manifests immediately.

I can see the signal on all power lines.


Any thoughts?


B

found one. Will need $50, but have to test it for you first. Will do that today.

Regards

Tim

On Saturday, July 19, 2014 4:19 AM, "Robert Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Hi Tim

Any news on the 150?


Cheers



Bob

On 18/07/2014 08:25, Tim Conniff tconno@... [yamahacs80] wrote:

dummy load may become pivotal in determining the source of the issue.

Alternatively, of course, you could substitute another source of power if available, and i don't mean another cs50 supply, I mean ANY other capable source.

Given the whine's prevalence on the power lines, you might also want to disconnect the juice to the voice cards all at once and see if it's still being heard, just to further rule out stuff.

Btw, I have found a 150, just haven't had time to check it yet.

good luck

Tim

On Thursday, July 17, 2014 11:38 PM, "Bob Stewart bob@... [yamahacs80]" wrote:

I don't have a dummy load unfortunatley, but did short the sense lines and look at it.

Seemed to be OK, but might need to run it for a while to let it warm up first.

Might just be that something's beginning to fail under load. Just really annoying that it's showing up on all the power lines. Might have a chance to look at it further today, but have a MonoPoly to tune, and a Prophet 5 to diagnose over at a clients.

On Friday, July 18, 2014, Tim Conniff tconno@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

Can you remove the supply, give it all needed dummy loads, and or short sense lines to their respective power lines? Then you can determine if it is strictly from the supply, or a function of the load inducing a resonant freq, or other anomaly. I assume you have a scope.

Tim

On Thursday, July 17, 2014 11:04 PM, "Bob Stewart bob@... [yamahacs80]" <yamahacs80@yahoogroups.com> wrote:

Only two fuses on the CS50.

Voltages are all there, but there's this signal sitting on top of them.

Synth works fine other than the whine, and a duff LFO chip.

Thinking it's got to be a duff semiconductor/ IC on the PSU :-(

B

On Friday, July 18, 2014, laurie laurie@... [yamahacs80] <yamahacs80@yahoogroups.com> wrote:

are all 3 fuses intact?

---- On Thu, 17 Jul 2014 11:14:08 -0500 bob@blzproductions.com [yamahacs80]<yamahacs80@yahoogroups.com> wrote ----

Hi


Just servicing a CS50, and it's constantly outputting a whine of about 4120Hz.

Unit came to me a bit battered as the PSU had shaken loose and trashed a few things inside.
PSU PCB had become cracked, so replaced that with a working one purchased from Synthparts.
Recapped the new PCB before I fitted it.

I've done the usual, changed the logic on the KAS board and the S/H board, replaced power decoupling caps throughout etc.

The only difference is that originally it took a minute or so to manifest... now it manifests immediately.

I can see the signal on all power lines.


Any thoughts?


B