ProKeys 88 with intermittent sound ... help with repair

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wonder
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ProKeys 88 with intermittent sound ... help with repair

Post by wonder »

I have a prokeys 88 that has an issue.

It gives little to no sound output and intermittently will crackle and then the sound will blast out (because I have my volume all the way up)...then crackle and the sound will go out or down to almost nothing at all.
There is also no headphone sound at all

I'd like to try and fix this issue myself and not pay to get repaired ... anyone else have this issue or know what to try to fix it?

I opened up the back panel and reseated the connecting ribbons but that didn't help. I tried jiggling some connections while the DEMO was playing to see if it was maybe a faulty connection but there's no correlation. I won't even touch the keyboard and it'll go into the intermittent crackling. I get full volume maybe 1% of the time it's on.

anyone help?
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by buzzsmith »

I hate this keyboard, if it's the M-Audio.

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Re: ProKeys 88 with intermittent sound ... help with repair

Post by wonder »

me too. that's why I'm fixing it to sell it.
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by mikehalloran »

I opened up the back panel and reseated the connecting ribbons but that didn't help.
My first suggestion is always to burnish the connectors - that's what you are doing, however.

Does it function fine cold and act up warm? If so, there are sprays that will cool components - hit them with "freeze spray" and see if it's a bad transistor or IC. If so, cooling the bad part should cause it to work again for a minute or two.

Other than that, a bad capacitor or resistor could be causing the problem. Anything looking burnt or leaking?

Any chance there's an undocumented memory keep alive battery?
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by wonder »


Other than that, a bad capacitor or resistor could be causing the problem. Anything looking burnt or leaking?

Any chance there's an undocumented memory keep alive battery?
The only thing I noticed were the solder points to the L and R jacks that are soldered to the mother board looked a little brown. Not totally burnt but def a dif color than the other solder points. I'm no circuitry pro. I'll post a pic.


Re: undocumented memory keeping battery alive -- I'm not sure what that means, sorry.

Re: it working cold/hot. There's no instance where it just "starts" working. When I turn it on and keep it on for a while its the same thing.

I'm not sure if it's just coincidence or not but I remember a while ago when it started happening I would sort of bang on the keys (to play louder notes) and the sound would "kick on" or get REAL loud....almost like it triggered or bypassed a short or something. Again, coulda been coincidence but if that's any clue...
Although now I tried the same thing and never got any sound above a whisper out of the thing.
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by mikehalloran »

A cracked solder joint or circuit board is what I would be looking for. Possibly a loose wire in a connector...

Many electronic devices have batteries that keep the memory alive. Not all of these batteries are documented or easy to recognize. Many are soldered in. It's not unusual for them not to be mentioned in the owners manual - you would need the service manual to be aware of their existence. Old techs sometimes call them "keep alive" batteries.
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by wonder »

Image

Image

Here are pics of the solder points I was referring to that look brown. I'm not sure if they're bad but here they are.
The connections in question are the L/R output jacks on the back of the keyboard.
What puzzles me is that the headphone jack doesn't have ANY sound at all.

At any rate ... does this help or point to anything?
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by mikehalloran »

It's time to break out a multimeter and see where the voltage is and where it isn't. That's the only way to find what's happening on each side of a discolored part, broken jack etc. Juice going into a jack but none coming out will tell you the jack or solder joint is bad and so on...
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Re: ProKeys 88 with intermittent sound ... help with repair

Post by wonder »

I'll borrow my friends and then can you help guide me through?
Or is it a bigger job?
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