No sound coming out of my KN2000

[Morticia001]

Good afternoon fellow Keyboardists, I have a slight problem.

I have been gifted the above keyboard and whilst it powers on and all the menu functions are working, there is no sound coming out of the speakers, or the output jack or the headphone jack. However with the volume turned up to max and an ear pressed to the speaker, it is just about possible to hear an incredibly faint sound from the speakers.

Has anyone had a similar experience and knows what the cause or solution is please?

 

[happyrat1]

Check your configuration to see if LOCAL is turned on or off.

 

[Gourockian]

Good afternoon fellow Keyboardists, I have a slight problem.

I have been gifted the above keyboard and whilst it powers on and all the menu functions are working, there is no sound coming out of the speakers, or the output jack or the headphone jack. However with the volume turned up to max and an ear pressed to the speaker, it is just about possible to hear an incredibly faint sound from the speakers.

Has anyone had a similar experience and knows what the cause or solution is please?

I have a Technics KN2400 which I also obtained for nothing as it did not produce any sound. Everything looked good when powered on, so the symptoms appear to be very similar to your's.

The good news is, assuming the fault is the same and assuming you are able to do a little soldering, it's an easy and cheap fix. I tracked down the problem to one of the voltage regulators on the Power Supply board (marked FAJ). You need a digital multimeter to check the output from these. It looks like the KN2000 uses 2 x negative 5v regulators and 1 x positive 5v. In my case the KN2400 has 1 x neg 15v and 1 x pos 15v and the negative one was only producing 0.7 volts but the positive was producing 14.94 volts. I ordered one of each from Mouser Electronics and replaced both and I think with shipping, it came to around $12.

If you need the service manual, you can download it here, free of charge. https://elektrotanya.com/technics_sx-kn2000_service_manual.pdf/download.html#dl It will provide info on opening up the case etc. to get access to the boards.

I hope this helps and you get it working again.

Regards,

Al

 

[Morticia001]

I have a Technics KN2400 which I also obtained for nothing as it did not produce any sound. Everything looked good when powered on, so the symptoms appear to be very similar to your's.

The good news is, assuming the fault is the same and assuming you are able to do a little soldering, it's an easy and cheap fix. I tracked down the problem to one of the voltage regulators on the Power Supply board (marked FAJ). You need a digital multimeter to check the output from these. It looks like the KN2000 uses 2 x negative 5v regulators and 1 x positive 5v. In my case the KN2400 has 1 x neg 15v and 1 x pos 15v and the negative one was only producing 0.7 volts but the positive was producing 14.94 volts. I ordered one of each from Mouser Electronics and replaced both and I think with shipping, it came to around $12.

If you need the service manual, you can download it here, free of charge. https://elektrotanya.com/technics_sx-kn2000_service_manual.pdf/download.html#dl It will provide info on opening up the case etc. to get access to the boards.

I hope this helps and you get it working again.

Regards,

Al

I located and replaced the voltage regulators and now there is a definite humming coming from the speakers but there is still no sound.

 

[Morticia001]

I have a Technics KN2400 which I also obtained for nothing as it did not produce any sound. Everything looked good when powered on, so the symptoms appear to be very similar to your's.

The good news is, assuming the fault is the same and assuming you are able to do a little soldering, it's an easy and cheap fix. I tracked down the problem to one of the voltage regulators on the Power Supply board (marked FAJ). You need a digital multimeter to check the output from these. It looks like the KN2000 uses 2 x negative 5v regulators and 1 x positive 5v. In my case the KN2400 has 1 x neg 15v and 1 x pos 15v and the negative one was only producing 0.7 volts but the positive was producing 14.94 volts. I ordered one of each from Mouser Electronics and replaced both and I think with shipping, it came to around $12.

If you need the service manual, you can download it here, free of charge. https://elektrotanya.com/technics_sx-kn2000_service_manual.pdf/download.html#dl It will provide info on opening up the case etc. to get access to the boards.

I hope this helps and you get it working again.

Regards,

 

[Gourockian]

I located and replaced the voltage regulators and now there is a definite humming coming from the speakers but there is still no sound.

That's not too good. Hum is often a sign of failed or failing capacitors so the next thing to look for would be any swelling of the metal end caps or traces of electrolyte leakage onto the circuit board. However, if you have the small surface mount capacitors, they don't usually show any obvious sign of failure.

I recently replaced all 74 of these on the audio board of my Yamaha organ, as once one of them fails due to age, it is likely that others will follow suit. This cured the problem of it only producing a crackling sound and it is back to working as normal.

They are easily removed just by twisting them off and if you are handy with a soldering iron, you shouldn't have any trouble replacing them. There are a number of videos on YT giving good advice on doing this.

Just a passing thought - I take it that you replaced the regulators like for like and didn't get them mixed up?

 

[Gunnar J]

Hi.
I once had a KN2000 that the sound all that sudden went off with a POFF. It's years ago, but the solution was to replace the "output transistors" that one way or another got blown out.
I was lucky and got it fixed under the warranty that still was valid.

 

[Morticia001]

Another thing that I have observed is that since i replaced the voltage regulators, the LCD screen is a lot darker than it was before. I'm not sure why that would have occurred?

 

[Gourockian]

I suppose it's possible, although unlikely, that one of the new voltage regulators is faulty. Have you checked the outputs to confirm they are all providing 5 volts with the correct polarity?

 

[Peter J Martin]

Pleased to hear people are minded to repair old Technics keyboards rather than chuck them. Great technology... and usually reliability... given their age.

 

[Gourockian]

Pleased to hear people are minded to repair old Technics keyboards rather than chuck them. Great technology... and usually reliability... given their age.

Yep, I agree. I still play my old KN5000 from time to time but the display screen is in very poor condition now. It was showing some slight deterioration when I bought it for $25, so can't complain.

 

[guscar66]

I fell into Technics ownership by accident---I was taking lessons with my 'standard' Yamaha 3series---but my tutor had a KN6500--- it was like night and day even to complete beginner . A mutual friend had an old 2600 that he gigged with back in the day ----I bought it for £40. It was like slipping into the leather seats of an old jaguar after driving a basic astra. My friend who was also taking lessons from same tutor and then had a wee go with my 2600----became unsatisfied with his Casio and bought a 6000 online. Unfortunately this had a serious fault (couldn't turn off the rhythm) .Early in my working life I was electromechanical/electronic systems trained so took on this new challenge of sorting his board. So started my involvement.
Let me say firstly----this is a big elephant you are trying to eat! whilst 'poke and hope' can work sometimes if a fault becomes physically obvious ---its a long shot. Really , unless very lucky with a previously noted common issue---even then its not a given. You will need to work it through. I don't know what your previous experience is so forgive me if I am teaching granny to suck eggs. You will require a circuit diagram and a basic knowledge of the symbols and what they represent. A multi-meter. A cheap one will do. Now since you say that there is a signal albeit a faint one , this is good ---it means that the 'digital' section is probably working so you can concentrate on the audio signal path. To chase this through one would use a 'scope --but back in the day we used high impedance ear-phones with one side grounded and the other side was a 'wander' lead connected through a capacitor ---this is not a critical value ----usually a 1mF or 0.47mF foil --anything really. This system works well . The multi-meter comes into its own when the signal disappears ---then you check voltages in that the supply is present at point checked---and the biases are correct. Now I am assuming that you know to stay clear of the input power section (250v) ----after that point the voltages present are all safe. Just go in with one hand on the probe---being careful not to short anything out (can have low volts but high enough currents to destroy components) the probe should ideally be insulated apart from the poking bit.
Some points of note -----the fact that your display has gone dark suggests that the negative supply has failed (LCD needs a neg. bias---or tail ) so maybe check you fitted the new regulators the correct way around. Electrolytic capacitors do have a limited life (specs claim 1000 working hours) ----they often used in signal paths as a cheap way of conducting low level signals around the board. Not so prevalent in more modern boards that have less of a pure analogue path. I 're-capped' an old Korg BX------159 caps!! -----a KN5000 has about 20.
Anyway hope this helps, and good luck.

 

[Gourockian]

I fell into Technics ownership by accident---I was taking lessons with my 'standard' Yamaha 3series---but my tutor had a KN6500--- it was like night and day even to complete beginner . A mutual friend had an old 2600 that he gigged with back in the day ----I bought it for £40. It was like slipping into the leather seats of an old jaguar after driving a basic astra. My friend who was also taking lessons from same tutor and then had a wee go with my 2600----became unsatisfied with his Casio and bought a 6000 online. Unfortunately this had a serious fault (couldn't turn off the rhythm) .Early in my working life I was electromechanical/electronic systems trained so took on this new challenge of sorting his board. So started my involvement.
Let me say firstly----this is a big elephant you are trying to eat! whilst 'poke and hope' can work sometimes if a fault becomes physically obvious ---its a long shot. Really , unless very lucky with a previously noted common issue---even then its not a given. You will need to work it through. I don't know what your previous experience is so forgive me if I am teaching granny to suck eggs. You will require a circuit diagram and a basic knowledge of the symbols and what they represent. A multi-meter. A cheap one will do. Now since you say that there is a signal albeit a faint one , this is good ---it means that the 'digital' section is probably working so you can concentrate on the audio signal path. To chase this through one would use a 'scope --but back in the day we used high impedance ear-phones with one side grounded and the other side was a 'wander' lead connected through a capacitor ---this is not a critical value ----usually a 1mF or 0.47mF foil --anything really. This system works well . The multi-meter comes into its own when the signal disappears ---then you check voltages in that the supply is present at point checked---and the biases are correct. Now I am assuming that you know to stay clear of the input power section (250v) ----after that point the voltages present are all safe. Just go in with one hand on the probe---being careful not to short anything out (can have low volts but high enough currents to destroy components) the probe should ideally be insulated apart from the poking bit.
Some points of note -----the fact that your display has gone dark suggests that the negative supply has failed (LCD needs a neg. bias---or tail ) so maybe check you fitted the new regulators the correct way around. Electrolytic capacitors do have a limited life (specs claim 1000 working hours) ----they often used in signal paths as a cheap way of conducting low level signals around the board. Not so prevalent in more modern boards that have less of a pure analogue path. I 're-capped' an old Korg BX------159 caps!! -----a KN5000 has about 20.
Anyway hope this helps, and good luck.

Great advice and information. I loved your comparison regarding the Jaguar and Astra, although it wouldn't mean too much to some folks on this side of the pond. Back in the day, I had some cheap and sometimes 'strange' vehicles such as a Moskovitch, Daf 66, Reliant Regal van (Del Boy) but always fancied a classic Jaguar Mk VII. Unfortunately, that never happened.