Old 09-21-2017, 08:25 AM   #1
pcartwright
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Default Digital piano MIDI out slowly dying

I have a Technics SX-P50 digital piano that I use to lay piano tracks. I use both audio and MIDI outputs, but I rely most heavily on MIDI. The MIDI output is beginning to skip notes and hang notes with more regularity.

I know it's the piano's MIDI out as I have tested multiple cables and another keyboard with REAPER and another MIDI program. The piano's audio output is fine, so it's not a keyboard contact issue. Thus I'm thinking it's an issue with a circuit board, the MIDI processor, or the actual MIDI out connector.

I can change the MIDI female connector myself, but I probably can't repair a circuit board or processor outside a good cleaning. It doesn't happen consistently, so what do you think the issue is? Any DIY repair people here who can give me guidance outside buying a new piano?
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Old 09-21-2017, 11:43 AM   #2
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I can change the MIDI female connector myself, but I probably can't repair a circuit board or processor outside a good cleaning. It doesn't happen consistently, so what do you think the issue is?
It's pretty much impossible to tell what the problem is without actually seeing and measuring the circuit. Even that might be a challenge if the problem is intermittent and also if there are no service manual/schematics available.

When you tested with another keyboard and cable, did you try that setup long enough for the problem to most likely appear? I mean, if it does happen eg. once every hour, you'd have to try with the other gear in same conditions and problem free for several hours, swap back to the old and verify that the problem appears soon enough again.

I see that this keyboard has also MIDI IN, have you tested that? Results would tell at least if it's only the MIDI OUT or maybe the whole MIDI board is acting up.

Other than that, using proper electronics cleaner wouldn't hurt but might not help either. When you have the board open, check all possible loose connections. If possible, check the circuit board tracks, especially on the edge of the board and where they lead to the connectors. Check to see if there's something suspicious on the connector pins where they are soldered into the board. Look for burnt marks, charred components, bulging or leaking capacitors etc. Take a few sharp enough close up pictures, especially if you see some suspicious components or connections. Pics might help others to suggest something more.

Last edited by xpander; 09-21-2017 at 11:59 AM.
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Old 09-21-2017, 12:16 PM   #3
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Only on smartphone at moment, so haven't looked this up extensively. A Digital piano from 2001 will be quite dated in terms of internal chipset performance and possibly key action too, at least according to the articles I read when picking my humble (bottom of the range) Casio. They alleged that older models (even expensive ones) did not compare well to recent designs. If this is true it might be worth checking out the latest graded hammer action keyboards, even relatively cheaper models. Competition has allegedly moved the game on substantially. If it was a really good one? you would want to check if a replacement has just a basic on off switch sustain pedal or something better.

I imagine if it was top of the range it would still be a decent controller, but only a hunch. I don't have experience with digital pianos of that age.

it could be an intermittent issue with components on the PCB. Failing electrolytic capacitors(check for spillage or bulging tops), or a dry joint somewhere, as well as the MIDI connector. Usually you won't see anything at all, but worth checking.
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Old 09-21-2017, 01:05 PM   #4
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Most of the times when I've had similar problems with my old hardware, the cause has turned out to be a solder joint that has failed.

It certainly fits the description of starting out as small intermittent failures, and failing more and more over time as the joint gets worse.
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Old 09-21-2017, 07:43 PM   #5
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First, thanks for the replies. Second, I found a maintenance manual for sale online. I should have it in a few days.

@xpander
The issue crops up randomly every minute or so, and yes, I tested the other setups extensively (I was kinda hoping it was in my head). I looked at the circuit boards, and I didn't see any obvious corrosion. Not that this completely takes away the circuit boards as the culprits, but I think I'll investigate the actual MIDI connector next.

Also, it doesn't seem to impact the midi input, though I haven't tested that as thoroughly.

@lunker
I tend to agree with your assessment and hope it's just a solder joint. I can repair that in a few minutes. Anything else would take hours/days/weeks and may not be effective.

@softsynth
I imagine newer models are better, but if I can repair this one with a new solder joint I will. Plus, this particular piano has a little sentimental value to me (as much as a digital piano could I suppose). It's true that it mainly acts as a controller these days, but it's gotten me through many gigs, college music coursework and my own musical meanderings. I'll keep it as long as I can. I might get an Arduino and try my hand at programming MIDI messages myself if it comes to that.
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Old 09-22-2017, 01:50 AM   #6
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@softsynth
I imagine newer models are better, but if I can repair this one with a new solder joint I will. Plus, this particular piano has a little sentimental value to me (as much as a digital piano could I suppose). It's true that it mainly acts as a controller these days, but it's gotten me through many gigs, college music coursework and my own musical meanderings. I'll keep it as long as I can. I might get an Arduino and try my hand at programming MIDI messages myself if it comes to that.
I only use my Casio as a MIDI controller. It has less polyphony than yours and only came out in the last year or so.

I have briefly considered Arduino to get an a faulty Roland A-800 (keyboard and modulation/pitch) working again. I couldn't find any existing projects to adapt for full keybeds with aftertouch.
That A-800 developed an intermittent fault (PCB), Roland repair cost was laughable (despite being a current model still available at the time I checked).

Anyway hope you find some way to get what you want for reasonable cost.
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Old 09-23-2017, 12:21 PM   #7
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If it's slowly dying as others have said it's very probably bad caps. I have a Technics SX-P30 here as a master keyboard (don't use the inbuilt sounds these days) but as an 88 note weighted keyboard I'm very fond of it) and it has performed flawlessly for probably 15 years, so they are very well made. A competent tech could almost certainly fix the problem for you; there are quite a few people who do this - check the Sound on Sound forums and you should be able to find someone. These boards were very well made and probably well worth restoring.
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Old 09-23-2017, 02:28 PM   #8
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If it's slowly dying as others have said it's very probably bad caps.
Yep. Electrolytic caps will degrade eventually. Not only they have a limited (and specifically stated) life expectancy in use but they also won't necessarily last ages just stored without use (the shelf life). Very common procedure when restoring old gear is recapping, replacing the old elcaps with the new ones.

There was also a time period when a lot of badly manufactured elcaps spread out to the market, affecting gear worse and way sooner than would normally be expected.
https://en.wikipedia.org/wiki/Capacitor_plague

So if these boards really are well made otherwise and especially if they have added sentimental value like in this case, recapping would make them serve and last that much longer. Even if a full recap would be considered, I would still start from solving the MIDI out problem first, of course.
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Old 09-23-2017, 06:07 PM   #9
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An added wrinkle. I just recorded about 5 minutes of miscellaneous piano stuff covering 4 or 5 different keys. There is definitely a trend as to which notes stick and/or don't sound. It seems that D4, E4, G4, C#5, E5, and D6 seem to be the major culprits.

That being said, I'm now thinking there may be an issue with the key mechanism.

EDIT: I don't have a clue at this point. If were an issue with a key, I would think I would have noticed it with one note in particular before now; not groups of notes getting seemingly worse.
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Old 09-23-2017, 06:59 PM   #10
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An added wrinkle. I just recorded about 5 minutes of miscellaneous piano stuff covering 4 or 5 different keys. There is definitely a trend as to which notes stick and/or don't sound. It seems that D4, E4, G4, C#5, E5, and D6 seem to be the major culprits.

That being said, I'm now thinking there may be an issue with the key mechanism.

EDIT: I don't have a clue at this point. If were an issue with a key, I would think I would have noticed it with one note in particular before now; not groups of notes getting seemingly worse.
EDIT 2: Just made a recording where the sustain pedal stuck.
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Old 09-24-2017, 02:04 PM   #11
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I have the service manual. The MIDI out path is fairly straight forward. I may try replacing components one at a time down the MIDI out line until I get it working.
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Old 04-21-2021, 04:29 AM   #12
Tom Gowe
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Default SX-P50 Service Manual

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I have the service manual. The MIDI out path is fairly straight forward. I may try replacing components one at a time down the MIDI out line until I get it working.
Hi @pcartwright - do you still happen to have that SX-P50 service manual? I have the same piano, and one of the output channels has failed. I'm seeking the service manual so I can see the schematics and attempt a repair, but I'm really struggling to get hold of one...
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Old 09-26-2021, 04:11 AM   #13
Karl Phazer
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I'd also be interested in the service manual!
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