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Viewing 1 to (10 Total) SX-PR250 low volume / muted keys in piano mode |
Ireland
Total Posts: 5
Joined: February 10, 2018
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Hello all. I'm an electronics hobbyist, and I offered to troubleshoot a volume problem with the digital piano (SX-PR250) at our church. It's a small church and the leadership has high hopes we can avoid the cost of buying a new piano if possible.
Having reviewed service manuals as well as other posts concerning volume issues, here's what I've observed:
1. The piano has power and plays at full volume in demo mode.
2. In piano mode the keys seem to function well-enough in that the correct sounds are being generated, and it does respond with a louder sound with a higher velocity strike, but overall, the keyboard volume is very muted and not loud enough to be of any practical use.
3. The master and balance volumes controls are in good position - again, it plays at good volume in demo mode.
4. I checked the settings for keyboard sensitivity (0-9) and that doesn't seem to have an effect.
It seems that many of the key components of the system are working - might it be as simple an issue as cleaning the contact switches under the keyboard?
Many thanks in advance,
Derek
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Posted on February 26, 2018 at 2:09 PM
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United Kingdom
Total Posts: 166
Joined: January 12, 2015
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Re: SX-PR250 low volume / muted keys in piano mode
Things to check!!!
First I hope you don't have a headphone adaptor in the socket as this will cut the volume and play all sorts of tricks with the levels!
The likely thing is not to do with the keys at all. Since the volume of each key is determined by key stroke velocity it is not going to be anything to do with the keys themselves.
You can try setting the piano back to its initial settings as it may have become confused. Use the control 2 button to move the LED to the initial point then use the transpose buttons to set the function to all then execute which will erase all the settings and put it back to factory settings.
have a listen to the speakers individually as there are 2 amplifiers and two sets of speakers one of which might be faulty. These are, if I remember correctly 6 inch drivers and there are so many of these that are pattern parts that will work as well as the originals if indeed you have a broken one.
let me know what you find. It is possible you have power amp failure on one channel. It is less easy to tell this from the piano itself as the sound is mixed such that there is a mono output across both amps with a minor left right enhancement to give the feeling of stereo. Easiest way to test is to try an input from the socket panel on individual inputs left and right. If you only have one channel then the speaker or amplifier is suspect.
Let me know what you find.
Regards
Dave
Posted on February 27, 2018 at 9:47 AM
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United Kingdom
Total Posts: 166
Joined: January 12, 2015
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Re: SX-PR250 low volume / muted keys in piano mode
One other thing..... try unplugging the pedals. If there is a short in the cabling here the piano section will think it is in soft mode so if the level gets better when you unplug the problem is in the cable or the pedal unit.
Dave
Posted on February 27, 2018 at 11:33 AM
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United Kingdom
Total Posts: 166
Joined: January 12, 2015
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Re: SX-PR250 low volume / muted keys in piano mode
On no account strip out the keys as you will then most likely have a wrecked piano that cannot be repaired without substantial cost and given this is over 25 years old there are no spares here!
Posted on February 27, 2018 at 11:35 AM
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Ireland
Total Posts: 5
Joined: February 10, 2018
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Re: SX-PR250 low volume / muted keys in piano mode
Dave,
Many thanks for the generous advice - I look forward to working through your recommended actions at the earliest opportunity. I'll let you know how it turns out.
Best wishes,
Derek
Posted on February 27, 2018 at 12:26 PM
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Ireland
Total Posts: 5
Joined: February 10, 2018
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Re: SX-PR250 low volume / muted keys in piano mode
Dave,
Here's the latest:
1. Reset to factory settings as you suggested - no change
2. Unplugged pedals - no change
3. Checked sound on all six speakers - all seem to be working and producing sounds in both piano and demo mode
5. I wasn't able to test inputs on the socket panel yet (trying to find my 1/4" connectors), but I did discover that when I turn down the "Right" Balance Volume on the control panel - all sounds in piano mode are lost and it doesn't matter what position the "Left" slide control is in.
Would that suggest a problem with the amplifier to you?
Many thanks,
Derek
Posted on March 1, 2018 at 6:47 PM
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United Kingdom
Total Posts: 166
Joined: January 12, 2015
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Re: SX-PR250 low volume / muted keys in piano mode
It could be the power amp stage but of course with everything in the same box the output of the left speakers shake the right speakers and vica versa. My guess is that although you can hear all the speakers it may be that the effect is actually a bleed over so it may be that the power amps are both working but the feed into the right channel isn't working. It might be a good idea to test the aux ins as this will give you a better idea if there is output on both channels. If the slider itself has failed (very possible) you will have to take it out and replace it. They may still be available if you shop around. I think in that model the sliders were alps made and single (not dual or stereo) pots. The other issue is of course that the switching at the headphone socket is broken and it is an open circuit switch here that is killing off the silent channel. Again its a straight forward socket swap.
Dave
Posted on March 1, 2018 at 7:18 PM
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Ireland
Total Posts: 5
Joined: February 10, 2018
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Re: SX-PR250 low volume / muted keys in piano mode
Dave,
I had a chance to text the aux ins using the audio output from my iPhone using the earphone jack. All the speakers seem to play at good volume using the volume adjustment on the phone. I thought it was strange the Master volume had no effect at controlling volume from aux ins. Would this be expected?
I also tried plugging in an old set of headphones and tested each of the 1/4" jacks. The observed problem of low volume in piano mode was replicated with the headphones, but just like the speakers, I couldn't detect a balance issue with left or right volume.
What would you suspect at this stage? Might it be worthwhile replacing the sliders and/or headphone sockets?
Thanks,
Derek
Posted on March 12, 2018 at 3:59 PM
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United Kingdom
Total Posts: 166
Joined: January 12, 2015
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Re: SX-PR250 low volume / muted keys in piano mode
Hi again
Can you try one more thing for me please.
The organ voice has no touch sensitivity on the keys, they play like a traditional organ and so sound at the same level from the keys no matter how hard you play them. The organ like much of the other sounds on the piano is a synthesis of the sound not a digital recording and as far as I can tell this probably is part of the first tone generator LSI IC. The other voices all come through the same digital to analog circuit and all the same reverb, chorus and filtering networks and the same mute circuit too. If this voice gives you a good volume from the keys then I have a feeling I know what the fault is.
If I understand your fault correctly it is likely to be that the LSI 2 tone generator IC may not be reading the Roms correctly as there may be a missing address line between the five chips. As such it is not possible to repair this without some substantial electronic test equipment (logic analyser) and even then it is not likely there will be individual replacement IC's available should it prove that there is a fault here. The Roms hold the piano sound in digital form and all 4 of them do the piano. If one address line is corrupt it is not going to be possible to fix this. There are 19 address lines shared between the Roms and the LSI driving chip and it could be any one of those lines at fault. Your only option would be to find a new board but given that the piano was made in around 1990 and that Technics stopped making these sort of things over 20 years ago it is unlikely you will find anything other than boards that have been recovered from scrap machines. There are no new parts available that I know of.
That is about the best I can give you without actually coming to you to run tests myself!
Regards
Dave
Posted on March 13, 2018 at 8:46 AM
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Ireland
Total Posts: 5
Joined: February 10, 2018
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Re: Re: SX-PR250 low volume / muted keys in piano mode
Dave,
Just a quick note to offer a tardy but most humble thanks for your generous support during the troubleshooting process. As per your last message, I think this is indeed a much trickier problem than I had first hoped, and it does look like an uphill battle going forward with a keyboard which is obsolete for replacement parts. Thanks again for the kind help and your excellent website.
Best wishes,
Derek
Posted on April 16, 2018 at 9:56 AM
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