[SOLVED] Ensoniq SD-1 keyboard calibration failure

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Jdo300
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[SOLVED] Ensoniq SD-1 keyboard calibration failure

Post by Jdo300 » Sun Apr 19, 2020 2:09 am

Hi Everyone,

I have an old Ensoniq SD-1 (KPC V233, ROM V4.10) that I've been using for years off and on, and about a year or so ago, it started failing the keyboard calibration test on boot. I've spent some time searching online for others with this issue and the most common answer was a bad header connector between the upper and lower coil boards underneath the keyboard. I opened up my keyboard to check on this, but on my model, it has already been replaced with the hard-wired ribbon cable. So, to get a better idea, I played with it a bit more to see what is going on.

If I just press ignore at the calibration prompt, all the other features of the keyboard appear to work as normal. I can still press most of the keys and they sound fine. But, I constantly hear the D2 and E-flat 2 keys triggering randomly whether or not I press anything. If I press D2, it sometimes plays and sometimes doesn't. If I
press the E-flat 2 key, it does nothing. I also noticed that there were four other keys on the keyboard, (C1, E2, A-flat 3, and C5) which if I press them, cause D2 to sound in a quick staccato fashion, along with the sound of the key I pressed.

I am an electronics engineer by trade, but I'm not sure where to start troubleshooting this. I took some photos of the keyboard [See here] along with the ribbon cable on both sides of the coil board, in case these could be helpful. Right now, my only guess is that maybe there could be a cold solder joint on one of the ribbon cable connections, but that's all I can think of right now. I really love this keyboard, and except for this problem, it had been working great. I would hate to have to trash it because of this. Any ideas?

Thanks!
Jason O
Last edited by Jdo300 on Fri Apr 24, 2020 2:55 am, edited 1 time in total.

Ashe37
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Re: Ensoniq SD-1 keyboard calibration failure

Post by Ashe37 » Sun Apr 19, 2020 2:36 am

Definitely don't trash it, at the very least, its worth parts.

Do the phantom sounds go away if you turn local off and trigger it from MIDI?

definitely try resoldering the cable.

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Re: Ensoniq SD-1 keyboard calibration failure

Post by Jdo300 » Mon Apr 20, 2020 10:26 pm

Ashe37 wrote:
Sun Apr 19, 2020 2:36 am
Definitely don't trash it, at the very least, its worth parts.

Do the phantom sounds go away if you turn local off and trigger it from MIDI?

definitely try resoldering the cable.
Actually, I haven't tried connecting it up to an external MIDI controller yet. I can give that a try and let you know what happens. As for re-soldering. I'm thinking to try that anyway just as a precautionary measure (I'm really hoping that is all it is in this case!) Will let you know what I find.

Thank you!
Jason O

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Re: Ensoniq SD-1 keyboard calibration failure

Post by Jdo300 » Tue Apr 21, 2020 3:51 am

Ok, I just did a quick test tonight with my MIDI controller (an M-AUDIO Uno USB Adapter). I connected it up to the keyboard and ran MIDI-OX to check what was going on.

If on the current sound, I disable local control, the phantom sounds do, in fact stop. I can still play any of the notes through the MIDI controller with no problem. But if I re-enable local control, The phantom notes play in my headphones and get sent out to my computer through the MIDI controller and recorded. Sooo.... it would seem that this problem points to a keyboard issue?

Tomorrow, I'm planning to bust out the soldering iron and reheat all the connections for the ribbon cable just in case there may be a cold solder joint there somewhere. Are there any other possible culprits that could be causing this behavior?

- Jason O

Ashe37
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Re: Ensoniq SD-1 keyboard calibration failure

Post by Ashe37 » Tue Apr 21, 2020 4:21 am

that's the extend of my knowledge. there's anotehr used here that can actually do minor work on them that may know... but i haven't seen him around. try resoldering.

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Re: Ensoniq SD-1 keyboard calibration failure

Post by Jdo300 » Fri Apr 24, 2020 2:54 am

OK I was able to fix it! However, the real problem wasn't the ribbon connector. I did reflow all of the solder connections just to be sure, but this had no effect at all. Later I took off the keys surrounding the two that were malfunctioning, and noticed that there was some corrosion on the coil board near the E flat key which was completely not responding.

So I took some alcohol and a wire brush and gently cleaned the corrosion from the area. Next, I measured the resistance of the coil in question, along with the surrounding coils for comparison. A good coil should measure out to around 1.1 Ohms, however, the E flat coil was measuring in at around 100 kOhms! A further inspection revealed that the trace was badly damaged at the point where it connected to the drive transistor. To correct the problem, I took a length of lead wire from a resistor and soldered one end between the transistor pad and a bare portion of the coil trace which I removed the solder resist from. After reconnecting the coil and assembling everything, it worked perfectly, passed calibration, and sounds awesome once more! Hoping this may help anyone else who may run into this problem. Thanks for your encouragement Ashe37 to look for solutions :thumbleft:

- Jason O

Ashe37
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TG-33, K3m, Blofeld, Micron, Mopho, BS II, JV-1080
Band: Eridani V
Location: Central VA

Re: [SOLVED] Ensoniq SD-1 keyboard calibration failure

Post by Ashe37 » Fri Apr 24, 2020 4:07 am

glad you fixed it and it was also an inhteresting find. my VFX, i had two keys where the AT was wonky- because the little metal plates on the keys were detached and pinned under the keys.

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Re: [SOLVED] Ensoniq SD-1 keyboard calibration failure

Post by Hyde » Fri Apr 24, 2020 5:14 am

Cool!
Makin' Noises

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