has anybody got a copy of the Yamaha dx9 circuit diagram I can’t find one online only the dx7 and they are different any help would be appreciated
Did you try YAMAHA DX7 DX9 Service Manual download, schematics, eeprom, repair info for electronics experts
Here you go
thank you for the circuit diagram very much appreciated
hi that one is not the correct one for the dx9. its for the dx7 and the boards are not the same
Yes they two are very similar but my link is indeed correct. The DX9 is a cut down DX7. There’s no Sub-CPU in the schematic so it’s the 9. The main chips including the FM ones are the same, so that there’s a custom firmware out there which will let you play 6-op patches on a DX9
yes i am aware of the differences …the reply about them not being the same was for sargfowlert regarding the link he sent for the dx7/dx9 service manual
Did the synth make sound at all since you first purchased or did it just stoo working after initializing it? I’m familiar with the Yamaha DX7. It may be something very simple like the volume slider. Maybe you can try using Deoxit spray inside the volume slider from the outside of your DX-9. I had a similar issue with a few preamp gain knobs on my recording console and the Deoxit spray solved that problem. Once you spray into the volume slider, then move the slider up & down about 15 times. The spray can comes with a thin straw. Make sure the DX-9 is not powered up. After you spray into the volume slider usung short quick sprays. Wipe any risidual spray off of your DX-9 with some damp paper towel. Then use a dry one, wait about 20 minutes befor turning the DX-9 power on to try the volume. If you hear any crackle or static noise. Turn the power off again and repeat this process. I had to repeat the process 3 times on my recording console’s preamp. I hope this helps 
how are you on the part of the circuit that generates the sounds {waveforms}
It’s difficult to tell with the DX9 because of the lack of patch names. But both the 7 or 9 will not make any sensible sound without valid data in memory. Much easier to tell on the 7 when this is the case cause the memory names are garbage. So you need to download some patches via sysex. First though check the battery is 2.8v or above. Then download the patches using sysex via the midi port, there’s a very good dedicated DX9 website which has plenty. If you get “MIDI Data received” at the end of sysex loading then you have sensible data in your patches. Obviously make sure both analogue voltages are present so +/-15v. If this is all good and there’s no sound it get tricky, you need scope, schematic and a lot of patience. First thing is to check that the “Two phase clock” is being generated so IC16 should have high frequency of a couple of MHz present at two of the pins, these reach the two FM chips via a custom Yamaha buffer chips IC36 and 37
hi sorry for the delay in my reply had to earn some money this week !!! done some more probing and the clock oscillator is running at the correct 9.4 MHz, I am getting 4.7 MHz at ic16 and at the input of ic36 and ic37 the outputs of ic 36 and 37 should go to pins 63 and 64 of ic2 and ic3 on ic2 I get 4.7mhz on pins 63 and 64 but on ic3 I get 4.7mhz on pin63 but nothing on pin64..im not sure but the does not seem right.
Yeah that’s not right. The buffer chips are dual devices so most likely half of one has failed. You can still get them if you search online it’s an IG something. Someone on this forum had the same issue a while back
well had a bit of success tonight I borrowed the ig07950 from my other working dx9 fitted it and now it is making sound albeit the basic sine wave as I have not loaded and sounds into it yet but it is still not how it should be it appears as though the sustain pedal is stuck on if you play a note it just holds the note, any ideas
Until you put some proper patch data in there you can get all sorts of weird stuff, so do that but yeah replace the battery otherwise you will have to do it at each power cycle.
It should provide a basic sine wave after voice initialisation and it does that fine..but it is holding the note on after you have released the key.. i have repaired a fair few of these in the last 30 plus years but never seen one do this..im going to look into ic 18 incase this has failed and is holding on the sustain