Powering a digital keyboard that was stored during 25 years: any advice?

[Los974]

Hi there!
I just found the old Yamaha PSR-70 keyboard my late daddy had bought in 1986. It has been packed and stored from the mid-90s to now.

Are there any precautions to take before trying to power it on again? Any advice to bring back into service such an old timer?

I tried to look for information on several websites, but found nothing really related to this question.

FYI, it is a 100% digital keyboard with a FM engine + samples for drums.

Greetings from Reunion Island,

Los

[crochambeau]

Gear like this this I tend to just plug it in and go. With the external power supply/wall wart if the PSU fails you can simply replace it. Do be mindful that Yamaha wants positive center on the power supply.

[Los974]

Thanks a lot for your advice. I will give it a try.

[Los974]

Here is the result of my attempt: it works ... a little!

It produces sound but none of the buttons of the control panel work: only the (analog) volume sliders work. However, I was able to browse part of the preset sounds via MIDI: it responds perfectly to MIDI but MIDI implementation was very poor at that time, therefore not so much can be done without the on-board controls.

Keybed works flawlessly, which is amazing regarding the age of the device.

Another problem: it generates the sound only to left channel, no stereo (either via audio output or headphones output).

I also noticed that the Power led is not as bright as it used to be: during the golden age of this keyboard, when powering on, it was half bright during one second and then fully bright. Now, it only turns half bright.

According to this link, it could be capacitor-related: https://www.yamaha-keyboard-guide.com/y ... sr-70.html

Any idea?

[crochambeau]

Sounds like you may have oxidization on switch contacts.

Sometimes they come back to life with repeated exercise and use, 25 years is a long span though, so neglect may have taken hold..

If the switches remain reluctant to wake up and you are comfortable with opening the instrument up and exercising all of the moving parts while flushing them with some contact cleaner (no residue electronics cleaner), that might bring the switches around. I've not been inside the particular model of yours, but sometimes the manufacturer packs so much stuff into those that disassembly can be challenging.

The lop sided output could be a similar type of fault such as one side of the volume control being "clogged" (only use electronics cleaner that *does* leave a lubricating film with potentiometers), it could also be indicative of a broken connection between PCB and connector, or actual failed electronics.

[Los974]

Thanks a lot, I really appreciate your help. I will follow your advices.

[crochambeau]

Good luck!

The power LED going dim could very well be dried capacitors on the power rail, if you have the tools it would be worth checking internal voltages. Again, I'm not familiar with this particular model, but it looks like service data is available on the internet - so that is encouraging.

[Los974]

Thanks! Indeed it is very encouraging that it still produces sound, indicating that digital circuits may not be damaged.

The very few sounds I could get were very impressive as they were in my memory. I should have been able to find similar sounds in FM synths emulations (I use Dexed, DX7 V and FM8) but none of them sound the same. That's why I would like to save this keyboard.

[SciNote]

I'm sure you've already checked this, but I figured I'd post the obvious... Are you sure that you are using an AC adapter that outputs the correct voltage and can supply the required amperage? The LED staying dim is what made me think of that.

[Los974]

Hi SciNote,
thanks for your contribution. Indeed, you are right, this is something to check.

In this case, I am sure that the issue is not related to the AC adapter because I also tried with batteries (because this keyboard can be powered either with batteries or an AC adapter). Same result in both situations.

Have a great day!

[Los974]

Hi there,
here are a few updates about this keyboard. It works from time to time and nobody is able to tell why.

It has been investigated by two different persons who are used to service vintage gears (both analog and digital), they found no particular issue. Their common hypothesis is that one of the IC may be faulty, but without the service manual they cannot go further.

The service manuals found online (for example https://elektrotanya.com/yamaha_psr-70_ ... nload.html) are low quality: schematics and photos are not visible enough for them.

Anyway, when it works, it is a digital delight This thing is so 80ish!!