I have a digital piano Technics PX203. It is acting weird. The keys seem all mixed up. Some treble notes sound like bass notes and vice versa and sustaining sound without pressing the sustain pedal.

If certain notes on your Technics SX-PR150 digital piano are playing at a lower volume than others, it's possible that there could be a few underlying reasons for this issue. Here are some steps you can take to troubleshoot and potentially resolve the problem:

1. Dust and Debris:
   • Check if there is any dust, debris, or foreign objects present around the keys and internal components. Dust or debris could affect the key's action and cause uneven volume levels.
2. Contact Cleaning:
   • If you're comfortable doing so, you can carefully open the piano and clean the contacts underneath the affected keys. Contacts that have accumulated dirt or oxidation might lead to volume inconsistencies. Use a clean, dry cloth or contact cleaner specifically designed for electronics.
3. Key Mechanism:
   • Inspect the key mechanism for any signs of physical damage, misalignment, or wear. Damaged or misaligned keys could lead to uneven volume levels.
4. Sensors and Sensors Board:
   • Digital pianos like the Technics SX-PR150 use sensors to detect key presses and control volume. If a sensor is malfunctioning or damaged, it could result in volume inconsistencies. Check the sensors and their connections for any issues.
5. Audio Output and Amplification:
   • Check if the issue is specific to the internal speakers or if it also occurs when using headphones or external amplification. If the issue is present across all audio outputs, it might be related to the piano's internal components.
6. Factory Reset:
   • Perform a factory reset on the piano to restore its settings to default. This can help rule out any software-related issues that might be affecting the volume levels.
7. Professional Inspection:
   • If the above steps do not resolve the issue, it's recommended to seek the assistance of a professional technician who is experienced in repairing digital pianos. They can diagnose the problem accurately and perform any necessary repairs.

Please exercise caution while performing any internal inspections or repairs on your digital piano, especially if you're not experienced in working with electronic equipment. If you're unsure or uncomfortable with the process, it's best to seek professional help to avoid causing further damage.

it can be repaired or replaced if the boards are still available
Take it to an authorized service to have it repaired and failing that some shops that repair micro wave ovens have the technical ability to repair items of this nature
may be a good radio technician or radio repair shop could also do the repair as it is basically an electronic ( wireless/radio) that is controlled by keys

Sometimes the contacts under the keys get dirty and must be cleaned. To do this you have to disassemble the keyboard,
carefully remove the PCB under the whole keyboard, locate the not sounding notes, remove tre siliconic stripe with the contact and gently clean the inside black conductive rubber pills with a cottonfioc and alcool.
Also clean the contacts on PCB.

On organ mode, in general, almost all brands of the modern keyboard, velocity setting is not enabled. Setting velocity is used to determine how much the level of the sound that follows how strongly you press the keys. It is really just to imitate the sound of vintage organs, which in the past, electronic organ technologi not use the velocity on the keys. So, how strong / slow we press the keys, the sound level will remain the same.
At the Piano mode,modern keyboard using setting velocity. This also to imitate an acoustic piano, which, if we press the keys slowly, the sound level will be slow as well, and vice versa.
So, in your case,at the same volume slider, try to play on the organ modes, note level. Moving to the piano mode and press the keys securely powered (full power). Then the sound level should be equal to the organ mode.
On modern keyboards, also included organ sound that added velocity setting. Usually found on the user bank.

On organ mode, in general, almost all brands of the modern keyboard, velocity setting is not enabled. Setting velocity is used to determine how much the level of the sound that follows how strongly you press the keys. It is really just to imitate the sound of vintage organs, which in the past, electronic organ technologi not use the velocity on the keys. So, how strong / slow we press the keys, the sound level will remain the same.
At the Piano mode,modern keyboard using setting velocity. This also to imitate an acoustic piano, which, if we press the keys slowly, the sound level will be slow as well, and vice versa.
So, in your case,at the same volume slider, try to play on the organ modes, note level. Moving to the piano mode and press the keys securely powered (full power). Then the sound level should be equal to the organ mode.
On modern keyboards, also included organ sound that added velocity setting. Usually found on the user bank.

Sounds like either there is a problem with a low frequency driver or perhaps an eq setting.
If you have an external (line) output, you can try sending the signl through another amp. If you have headphones, then try them also. If the headphones sound distorted as well,then see if you have the eq to high on the bass.
Other than that, it could be a filter capacitor in the power supply. You would need some experience fixing that.

Also, in addition to more info I need; look on p 91 of the online owner's manual linked below. Pay attention to Sounds and Effects, the first section therein. Follow the directions closely, esp., read pp. 26, 83, and 86 which are referenced for detailed help w/ sound issues. TECHNICS SX PR305 Manual Page 91

Your piano was made in 1970.

with mixing, get the bass right, then add the piano/pad sounds then bring up the drums til it sounds good.