Hello, I’m looking for some help. I’ve come in possession of an Ensoniq ESQ-1 that’s not behaving itself. There are two issues which may be related or not. I have searched the forums for guidance which has helped in some ways but hasn’t got me to the root cause. I’ll explain the two issues and then I’ll explain what I’ve tried so far from what I’ve read to help speed up any trouble shooting.
Issue 1:
I have what sounds like a phantom key being pressed randomly and at a higher register than what’s default for the keyboard. when on the Piano 1 sound it sounds like random morse code of a very high pitch key being played, when I switch to a different patch its more of a high pitch squeal. The pitch and modulation wheels effects the sound of it too.
After some reading on here and other sites I’m able to stop it by pressing and releasing quickly lots of keys, this doesn’t always work first time, and sometimes requires a lot of fast repeated hits and then it stops. Then I play a note and all is good, but when I play the second note it comes back again.
Issue 2:
Every 8th key does not play, starting from the first G note on the left .
What I’ve tried so far
Check the voltages against the service manual - they all seem to be good.
pulled out all power connectors and ribbon cables and put them back in and out again to hopefully scrape away any oxidation.
I’ve replaced all of the capacitors on the power supply board with Panasonic caps.
I’ve tapped and pulled all the socketed IC’s out and put them back in.
I’ve cleaned all the Keyboard springs and rails they contact to remove any oxidation.
I’ve checked, visually the circuit board on the keyboard for corrosion, and looks to be okay. nothing significant to what I’ve seen in other posts where jumper leads have been used to bypass the corrosion.
I’ve done soft restarts - this does not get rid of the noise, only bashing lots of keys sorts this out, until I press the second note.
I’ve tried a hard reset, by de-soldering the 3V battery and soldering it back.
the voltage on the 3V battery is at 2.7V, not sure if this is too low. but from what I understand this should only effect the functionality of saving user patches.
I’ve also checked the filter values and they’re between 145 & 148,so within range.
I’m a bit of a novice at all this and not familiar with the ESQ-1 or synths in general, so any help regarding this would be much appreciated.
Thanks for the help. I was literally a out to update this. Since posting I’ve I have read other posts suggesting an issue in this area. However, since my original post, I have re-flowed all the solder joints on the keyboard connection on both the keyboard PCB and main board PCB, and also the back of the IC chip holder (u9).
I’ve then checked for continuity with both boards connected via the ribbon cable and it all checks out okay from the keyboard all the way to the IC chip holder. There were just two pins not getting a reading at the IC chip holder, but it was okay at the ribbon cable connection on the main board. But this checks out okay from the schematic you kindly linked, as those two pins say “nc” which I assume means not connected.
I’m starting to think that chip U9, has gone bad. This is what I’ve seen others call the keyboard logic chip (65002b). Which I’m guessing could also be the cause of the issue 1 as well.
Any other suggestions or thoughts would be greatly appreciated. Or if you or anyone could confirm my suspicions that this chip is bust that would help, and if anyone knows where I might be able to look for a replacement that’ll be great.
Otherwise I might have to turn this thing into a rack unit since it works fine with an external midi controller keyboard.
I doubt the IC is broken. Then it shouldn’t work at all
The next will be to check the whole matrix with an oscilloscope.
The chips sends on the lines PB0 - PB7 a signal (one output after the other).Assumingly this are longer pulses.
On PC0-PC7 it will receive those signals, but not those longer pulses, but eight short pulses on each line.
The same should happen on PD0-PD7. But this time all keys have to be pressed (place two square wooden sticks on the keyboard, one on all the white keys, one on all the black keys, and then place a weight on both sticks to push down all the keys).
I assume you will find on one of these ports the signal missing. That is the one, where the line from the chip to the key-switches is faulty. Assumingly a diode in the path is broken.
Thanks for the help, unfortunately I don’t have an oscilloscope, so not sure I’ll be able to investigate.
I have put my multimeter into diode test mode and I’m getting a voltage across all of the keyboard diodes in one direction and 0v in the other direction. Would this not suggest the diodes are ok. Or perhaps there’s not enough load going through to cause the failure?
If you have any suggestions I could look into, using a multimeter that would be great. Otherwise I might have to give up or look for someone local to have a look.
Interestingly though. I’ve not had the keyboard on for a while, one to have a break but also waiting for a new ribbon cable to arrive as I thought, I might as well try for only £3.
Any way, I switched it on and although every 8th key was still not working, I was able to play it for a whole 2 - 3 mins before the random phantom key pressing started. Note: from earlier: this key sounds like it’s a couple of octaves higher than what’s possible on the Keybed.
It’s as if something had to warm up, or a cap had to charge up before it could make this phantom sound.
![http://audiopro.r-massive.com/Ensoniq/Schematics/Ensoniq%20ESQ-1%20Digital%20Board%20(Rev.%20H)%20[black%20adjusted%2C%20300%20DPI].jpg](http://audiopro.r-massive.com/Ensoniq/Schematics/Ensoniq%20ESQ-1%20Digital%20Board%20%28Rev.%20H%29%20%5Bblack%20adjusted%2C%20300%20DPI%5D.jpg){kind=link}