Yamaha CS80

Hello,

Would it be appropriate to replace the +8/-6.5 side of a CS-60 psu with a pair of adjustable regulators? Its a pain finding some of the Japanese parts.
The digital portion of the circuit couldn't be more than a dozen or so CMOS, right? What kind of current requirements would be put on that supply? I've got NTE956/957 on hand so it would be an easy enough fix.
Also, why the seperate COM1 and COM2 on the psu? To keep the digital noise out of the signal ground? Should I get *roughly* correct reading measuring the +8/-6 rails from COM1? IE is something messed up if there is a big DC offset between the 15/-5 and the 8/-6 supplies?

Best,
Cooper

what parts are you looking for? There's nothing there that you can't substitute.

--- In yamahacs80@yahoogroups.com, "bcoopersloan" <mistercooper@...> wrote:
>
> Hello,
>
> Would it be appropriate to replace the +8/-6.5 side of a CS-60 psu with a pair of adjustable regulators? Its a pain finding some of the Japanese parts.
> The digital portion of the circuit couldn't be more than a dozen or so CMOS, right? What kind of current requirements would be put on that supply? I've got NTE956/957 on hand so it would be an easy enough fix.
> Also, why the seperate COM1 and COM2 on the psu? To keep the digital noise out of the signal ground? Should I get *roughly* correct reading measuring the +8/-6 rails from COM1? IE is something messed up if there is a big DC offset between the 15/-5 and the 8/-6 supplies?
>
> Best,
> Cooper
>

I wish I were certain, ramcur was kind enough to send me an assortment of
pulls to swap out, I feel like I must have already replaced most of the
transistors and diodes, I suppose its possible one got zapped in the
process. I'm poking about with my meter now.

Cooper


[Non-text portions of this message have been removed]

Here's what you need to do:

1.) Don't worry about the ground.

2.) Take pictures of the thing before you take it apart. Make sure that all component orientation is legible and that you can identify all of the components with their respective places.

3.) As a general rule, avoid NTE subs.

4.) Take note that the whole thing is interconnected. +15 and -15 are referenced in the +8.5 and -6.5 If a +15 or -15 is down, your PSU won't work.

5.) Make sure that you use jumpers for the sense circuits if you are powering up the PSU unloaded.

6.) Pull out Tr710, Tr711, Tr712, Tr714 and D712 - use the multimeter diode test to determine if they are not dead. Check Diode D715 with the power on because it is a Zener; it should read about 15 volts across the anode and cathode. Also check D713; it should read about 6v (guess) when everything else is working.

7.) Replace the OP AMP

8.) Check to make sure that the fuses have continuity.

9.) Check the 1k resistors that are going from the Emitters of TR711 and TR712 to ground. Check the .47 ohm resistors from Tr709 to Tr714.

10.) Check Tr709 and Tr714 like you did with the small signal transistors. These are located on a different panel of the PSU under the fuses in the middle and can be easily overlooked.


If you need help crossing the transistors, or have any questions, let me know.

-Mike

--- In yamahacs80@yahoogroups.com, "B. Cooper Sloan" <mistercooper@...> wrote:
>
> I wish I were certain, ramcur was kind enough to send me an assortment of
> pulls to swap out, I feel like I must have already replaced most of the
> transistors and diodes, I suppose its possible one got zapped in the
> process. I'm poking about with my meter now.
>
> Cooper
>
>
> [Non-text portions of this message have been removed]
>

Don't forget to test all of your soldering with a multimeter for continuity from solder pad to pad, and inspecting with a magnifying glass couldn't hurt either. Also, the nature of the PSU design makes it very easy to terminate a connection with excessive handling: the wire connections break when you flip flop the board too much.

-Mike

--- In yamahacs80@yahoogroups.com, "Mike" <mborish_2000@...> wrote:
>
> Here's what you need to do:
>
> 1.) Don't worry about the ground.
>
> 2.) Take pictures of the thing before you take it apart. Make sure that all component orientation is legible and that you can identify all of the components with their respective places.
>
> 3.) As a general rule, avoid NTE subs.
>
> 4.) Take note that the whole thing is interconnected. +15 and -15 are referenced in the +8.5 and -6.5 If a +15 or -15 is down, your PSU won't work.
>
> 5.) Make sure that you use jumpers for the sense circuits if you are powering up the PSU unloaded.
>
> 6.) Pull out Tr710, Tr711, Tr712, Tr714 and D712 - use the multimeter diode test to determine if they are not dead. Check Diode D715 with the power on because it is a Zener; it should read about 15 volts across the anode and cathode. Also check D713; it should read about 6v (guess) when everything else is working.
>
> 7.) Replace the OP AMP
>
> 8.) Check to make sure that the fuses have continuity.
>
> 9.) Check the 1k resistors that are going from the Emitters of TR711 and TR712 to ground. Check the .47 ohm resistors from Tr709 to Tr714.
>
> 10.) Check Tr709 and Tr714 like you did with the small signal transistors. These are located on a different panel of the PSU under the fuses in the middle and can be easily overlooked.
>
>
> If you need help crossing the transistors, or have any questions, let me know.
>
> -Mike
>
>
>
>
>
> --- In yamahacs80@yahoogroups.com, "B. Cooper Sloan" <mistercooper@> wrote:
> >
> > I wish I were certain, ramcur was kind enough to send me an assortment of
> > pulls to swap out, I feel like I must have already replaced most of the
> > transistors and diodes, I suppose its possible one got zapped in the
> > process. I'm poking about with my meter now.
> >
> > Cooper
> >
> >
> > [Non-text portions of this message have been removed]
> >
>