Roland HP-1 Electric Organ/Keyboard audio output noise

[ben7]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Just to see I'm going to disconnect the headphone jacks, there are 2 of them, at the amp/power board side. I doubt this is causing the fault but worth a try to eliminate.
I did read somewhere in my travels someone had a curious sound issue and had something to do with the headphone jack.

So, what did you find when you did that?

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

I think what happened is what would be expected to happen.

Pins
1 Sig L
2 Sig R
3 AGnd
4 Mute Send
5 Mute Ret
6 LED K
7 LED A

removing the 7 pin plug the piano switched on but the power led did not light up (Pin 6&7), no sound at all - Pin4&5 (no fault noise or key stroke tunes) either from built-in speakers or headphones obviously.

So I removed just pins 1 and 2 Sig L and R, piano powers up with led and still get the faulty noise through the speakers.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Solder side of the Main board.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

So, I'm going to connect an external speaker to the 'Output' jack, looking at the schematics this will bypass the Equaliser and Amplifier circuitry.
These I take it would need to be powered speakers?

If possible I shall then also try connecting an external input, which would presumably bypass the sound generator circuitry on the main board.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Theres also a Local Control On and Off function which is for connecting MIDI devices, in the off state 'the keyboard and the internal sound generator are in an unlinked state. No sound will be produced by the keyboard when it is played.'

The faulty noise still persists with this on or off.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Hacked a few wires and mashed up a connection between the piano input/output jacks to a Logik LOGLM101DU Micro Hi-Fi System.

Connected powered external speakers and get 'fault' noise through both left and right speakers with volume on piano turned up only.

Connect an Aux input and plays through the pianos internal speakers fine, the 'fault' noise only occurs when the volume on the piano is turned up.

Not sure exactly how conclusive this is?

Does this narrow it down any?

[ben7]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Hacked a few wires and mashed up a connection between the piano input/output jacks to a Logik LOGLM101DU Micro Hi-Fi System.

Connected powered external speakers and get 'fault' noise through both left and right speakers with volume on piano turned up only.

Connect an Aux input and plays through the pianos internal speakers fine, the 'fault' noise only occurs when the volume on the piano is turned up.

Not sure exactly how conclusive this is?

Does this narrow it down any?

Does the noise change if you just tap the volume POT?
It sounds like a bad op-amp or bad (noisy) resistor.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

No, doesn't seem to make a difference tapping or twiddling the volume knob.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Would it be possible to disconnect on Power/Amp Board CN4 Pins 10 LeftCh Signal, 11 AGnd and 12 RightCh Signal (these are AOUTL+/- and AOUTR+/- on AK4324 96kHz Sampling 24Bit DAC) and connect directly to speakers, bypassing the Control PCB i.e master volume and bypassing Power/Amp board.

[notallbad]

Re: Roland HP-1 Electric Organ/Keyboard audio output noise

Still no success fixing this but an update:

Scope connected to CN8, Agnd (Pin 11) and LeftCh-Signal (Pin 10) or RightCh-Signal (Pin 12) and get the 'noise' waveform. Also get the 'noise' waveform on pins 1 and 7 of the M5218AFP - Dual Low-Noise Op-Amp.

The next step is to check between the 96kHz Sampling 24-bit DAC (AK4324) and the Op-Amp (M5218AFP).

Not really sure how to check before the DAC and getting the feeling that if the fault is before the DAC the problem is going to lie with an I.C.