CLP-340 Power Supply


I am looking for some some specifications on the transformer X8264 and the power supply board X4384 for a CLP-340 Yamaha clavinova – especially before I start ordering parts I cannot return.

I have “output” from the transformer, but I don’t know if correct voltages. The power supply board has no output, I never hear the relay. No caps are bulged, no signs of burns. All fuses appear intact.

I was able to find the service manual but it is not that clear.

Has anyone had luck fixing these power supply boards and if so can you provide guidance? I have tech skills, DVMs, oscilloscope, soldering/resoldering etc.

Thanks in advance

Have you got any voltages at all - 3,3VD1, 3,3VD2, +5VD1, +12VDC -12VDC ?

The relay is fed by the +12VDC and controlled by the amp output - ie no DC on output.

The brown long thing is a DC/DC converter … don’t break it … very rare !!!

All voltages seem OK. +3.35, +5.1 D1 & D2

Only minor change for +12 is 11.7, -12 is -11.6

VCC+ is 26.6VDC, referenced to +3.3/5’s ground

Output from xformer (Volts AC, color pair)
13.9 green/yellow; 40.7 red/white; 34.7 blue/orange

At this point I am focusing on DM module, would some suggestions.

Happy with that … the relay not engaging may be caused by one or both output of the SANYO 40W x 40W chip.

find these two resistors (in picture) on the Power Supply board and measure the voltage to ground.


Looks like J’s on top side may help measure the TR2 & TR3 voltages (red circles).

BOTH of these are 0V (zero).

So I should point out that although I have the red LED ON (left side of keyboard), neither the main 3digit display nor any other indicator lights are on.

Double-checking the R34/R35 jumpers, same line as your yellow markings: 0V

No display - that is an entirely different story now!!!

The relay is kept off by a /MUTE signal from the CPU … if the CPU does not run that /MUTE signal is kept down - hence the relay won’t pull.

Now have to look at the main board instead!!!

There are two IC’s on there that make 1.2VDC (IC2) and 1.5VDC (IC302) respectively from the 3.3VDC supplied from the PSU. Check both Vin and Vout on both.

At the same time also check the /RESET signal from out of IC3.



All good unfortunately.

IC2, Pin1/4: 3.32V Pin5: 1.17V
IC302, Pin 1/4: 3.28V, Pin 5: 1.47V
IC4, Pin7 3.32, Pin6: 3.32V, Pin6: 3.32V, Pin2: 0.13V
IC3 Pin1: 3.32V
R18: 3.32V (/RESET)

Have you got access to an oscilloscope ?

Next we need to check if the clocks for the CPUs are running -

Yes I do, 100MHz Tek, 10MΩ probes. Let me know what lines are best. Not a storage scope though, so I cannot capture transients. It’s on my wish list – logic analyzer in general.

Here is what I found so far on schematic:

On CPU (SWX02): Pin 13 (16.93MHz out)
On SWP51L (tone generator): Pin 208
DM9000AEP (X7029A00) LAN Controller, Pin 19

How about any of the CLK signals?

I just read through real fast . Relay not engaging? Replace it ! Continue on from there.
I have got caught many times by a bad replay. You can also pull it out and test it with a bench supply. For the cost better to just put a new one in.

Sampler1: Yes the relay on the bench works great, all within spec.

To any and all following this: I am taking a break to fix a few other easier projects. However, it dawns on me the 40W power amp might be the issue. The relay works fine (tested on bench) but the signal lines are low, inhibiting the relay’s activation transistor. /MUTE was high last I checked.

Fortunately these amps are still readily available but will need to desolder to verify on bench.

Short of this idea, the only thing left is either race condition with DM board or simply logic. Logic analyser is in order.

Suggestions appreciated.