DX9 shows "Replace Battery" even after replacing it

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I recently acquired a DX9 that does not produce sound and displays a “change battery” message on the display.

I searched the internet and only found the schematic drawings of the DX7, the available service manual that I found goes up to page 24 but the schematics of the DX9 are on pages 25 onwards. If anyone has these drawings and can share them with me I would be very grateful.

Well, I opened the DX9, found the 2 4200mF capacitors on the power supply swollen, I replaced them, I did not replace the rest of the capacitors on the main board because in ESR tests they were all perfect, but I will replace them later.

The battery was actually at 0V, I removed the battery, installed a 2032 battery socket, installed a new battery and made sure not to install it upside down. Since I don’t have the electrical drawing of the DX9, I based myself on the DX7 schematic, which has modifications, because in the DX7 after the battery there is the so-called diode D4, but in the DX9 there is diode D2, but following the information, after installing the new battery, I can read 3V on my multimeter on pins 24 of the 2 RAM memories when the DX9 is unplugged from the power outlet. When I plug the DX9 into the outlet I can read 5V on pins 24 of the RAM memories, so I think the battery part is correct now. But when I turn on the DX9 it continues to show the message “replace battery!” Even after changing the battery and being able to read the 3V on the memory pins it continues to display “replace battery!”. I press the MODE key and press the 20 key until I reach the voltage reading and the display shows 0.0v. So the CPU is not receiving the battery voltage value, some analog to digital converter component should receive the battery value and inform the CPU, but this does not seem to happen. In the DX7 schematic there is an A/D converter M58990P that receives the 3v signal from the battery on its pin 4 which is the IN6 of this component, I believe it should be responsible for transforming the 3v signal into digital and informing the CPU, but in my DX9 this chip has pins 5, 6 and 7 grounded to GND, so it has to be another pin, so I need the schematic to be able to proceed correctly. This is assuming that there is no other problem. Anyway, I tried to get the original pressets from the internet at DX9 Patches, I downloaded them and using an interface with the Bomesend software I sent them to the DX9, the website above shows the steps to disable memory protection and enable reception, the DX9 accepts the connection and at the end shows the message “received” on the display, so I believe that it is actually receiving DUMP data from the patch, but no presset name appears on the screen and there is no sound coming from the device, and if I turn the device off and on again it displays “replace battery” in the same way. I may have a problem with the sound generation, but the sound may not be coming out because the memory is scrambled and the DUMP is not being done correctly either, so I first need to solve the problem of the CPU recognizing that the drums are present and make sure that I am doing the DUMP correctly, and only then, when I already have timbre names on the screen “piano”, organ"… etc., I can try to see if the sound comes out or if I need to fix something else related to the sound.

Did anyone understand what I said above?

Does anyone have this electrical schematic containing the DX9 and can send it to me?

Is there anything else I can test?

Thanks,

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I got home and went to the DX9. here we go. on pin 2 of the IC8 which is an A/D converter, we have a 10m resistor in series with the positive of the 3V battery. This resistor is altered, I removed it and measured 12.4M, I found it high, so I got some new resistors and joined 3 of 3m + 1 of 1m all in series and got a 10m reactor., put it in the circuit, now I really have 10m between pin 2 and the positive of the battery, but I only read 0.4v on pin 2, then I did a test, removed the 10m resistor and put a jumper, now I have pin2 connected directly to the positive of the 3v battery and I still read 0.4v but I noticed a slight heating of the ci8, so slight that I get confused if it really heated up. so I decide to remove the ci8, after removing it I read 3v on the pad where pin 2 was. This says that 3v arrives at pin 2, but when it is plugged in there is a voltage drop that pulls the 3v to 0.4v. I measured the resistance from pin 2 to the GND pin of the IC with a resistance scale and it is 6M ohms. I measured all the other inputs of this IC and they all have approximately 6M ohms. In other words, all the INs outside the board measure approximately 6M ohms for their GND pins. But when I put it in the circuit, it drops the voltage to 0.4V. I removed the 0.01 capacitor that is there between pin 2 and GND, and it doesn’t change anything. So I believe that the IC has some internal problem that causes the current to be drained to GND. I did one last test, with the IC soldered to the board, I released the resistor to isolate the battery and injected 3V with my bench power supply on pin2 and the negative on the GND of the motherboard. The current consumed by pin 2 is 0.19A, or 190mA. I thought that was a lot for an analog input, right? For this great one, I think I should change the IC 8 M58990P, but I only found it on Aliexpress. I will buy it and pray that it works.

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Some great detective work there I would say you found the culprit indeed. I got the same chips a while ago from UTSource and they worked fine, I would say it’s the same as getting them from AliExpress so should be fine

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Hi, I think at this point you need to do a factory reset. The instructions for Yamaha DX9 are on google. It’s a very simple process. Turn off DX9 , hold down the voice buttons while turning on power, it asks a question, I don’t remember the question.. Maybe it was like Reset? Then just press the plus :plus: button for Yes. After that turn it off then back on for a Factory Reset. I bet this will help you bro.

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Hi, I looked for this information on how to reset the Dx9 and I didn’t even find it in the manuals. Can you tell me where you found it?

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All I did was go to goggle.com and try searching for the schematics you were looking for. I noticed you mentioning no sound and already replaced parts. Then I typed in: How do I reset DX9 to factory settings. The information came right up. I searched for this because I’ve run into similar issues on a few different synths and samplers after doing a firware update also on modular synth modules like the Erica Synths LXR-02. The factory reset was necessary after updating firmware or repairing battery like on my Korg Wavestation. I had to change it’s battery because the screen said error even after just changing it’s battery. In order to complete the repair, I then also needed to factory reset the machine. Same with replacing the power supply on my ASR-10 keyboard. They need a factory reset after repair. I’ve also run into the no sound on my Yamaha DX7 after changing it’s battery. I had to do a factory reset. It’s a simple process. Go to google.com and type in the following exactly as it is here… don’t leave anything out. “How to factory reset the Yamaha DX9”. Contact me back if you can’t find it and I’ll take a screenshot of the simple instructions ok. Hope this helps. P.S. make sure you’re using google to find this info. Let me know how it goes. I’m happy to help out a fellow musician/ engineer.

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Hey Mike, thanks a lot for the contribution.

I asked you where you found this information because I had done previous research and found a lot of different ways to reset the dx9 to factory settings, and none of them work. I tested it, but I haven’t tried the one you’re describing yet. I’ll try it tonight and post the results.

I have no doubt that the firmware is messed up after changing the battery and needs a reset. But as I reported, the voltage value that arrives at pin 2 of the M58990P A/D converter is 0.4v with the new battery, and that leaves me puzzled… unless it’s on purpose that the internal resistance of the component together with the 10M resistance on the battery line throws the voltage to 0.4v so that the chip understands that 0.4v is a full battery and a lower value is a low battery… or something like that… but since I don’t have much information, I have to believe that the component is damaged. But I won’t be surprised if I do this factory reset successfully and it returns to reading 3v.

I’ll try…

Does anyone have a DX9 and can use a multimeter to measure the voltage value read between the negative terminal of the board and pin 2 of CI8?

What if a working DX9 has the same value of 0.4v on pin 2 and that would be correct…