Yamaha P85 Keyboard Hack

July 15th, 2011
hardware_hacking, keyboard, music
My yamaha p85 keyboard has internal speakers and two headphone jacks. Plugging anything into either headphone jack turns off the internal speakers. I think the intended use is for a student and teacher to both be able to hear while not bothering anyone else. For my purposes, though, it can be annoying. If I'm playing and I don't have good (or any) monitors, I would often prefer to have the internal speakers remain on so I could hear myself better. Luckily, the internals are relatively simple and this behavior can be modified.

I opened up the keyboard (instructions from the last time I did this) and found the board controlling the output jacks. It looks like this:

The big solder bits are where the two jacks connect. There are six pins. From looking at the traces (sorry about the poor focus) I could see that the middle two were connected together and the top one is grounded. Testing with a multimeter set to resistance, the middle two pins were normally connected to the ground, but disconnected when a cable was inserted. Looking into the jack, I think maybe the end of the cable pushes apart two bits of metal to break a connection. If we could short circut this detection circut, so that it always read "connected" then the internal speakers would stay on.

I considered short circuting both detection loops and then adding an externally accessible switch to disconnect them, but I decided against that because of the inconvenience of cutting a hole for the switch and mounting it. Instead I decided to modify only one of the jacks so that I would later be able to choose whether to leave the internal speakers on by plugging into one jack or the other. Some soldering later and we had:

It worked exactly as I had hoped. I closed everything back up and made sure it worked before putting in all the screws. Then I painted the modified jack with some white-out. Total time: 3hr.

Now to see how well the internal speakers do at a dance!

Update 2012-05-29: This is working pretty well. You still want a monitor so you can hear yourself, but it's now loud enough that if you can't get a personal monitor with just you as a supplement to the overall monitor mix it's not that bad.

Comment via: facebook

Recent posts on blogs I like:

Book Review: The Myth of Sex Addiction

I. David Ley’s The Myth of Sex Addiction is a stupid, wrong book saved only by the fact that the people it’s arguing with are stupider and wronger. II. “Sex addiction” is a proposed mental health condition, not recognized by the DSM or the ICD, where a pe…

via Thing of Things March 7, 2024

Your wedding doesn’t have to be that great

Your future happiness does not depend on how gorgeous this one day is. The post Your wedding doesn’t have to be that great appeared first on Otherwise.

via Otherwise March 4, 2024

When Nurses Lie to You

When the nurse comes to give you the flu shot, they say it won't hurt at all, right? And you trust them. Then they give you the shot, and it hurts! They lied to you. A lot of nurses lie to children about shots and blood draws. Part of it is they probabl…

via Lily Wise's Blog Posts February 28, 2024

more     (via openring)