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Korg SV-1, bulb lights on but not front pannel !

 
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Musella



Joined: 08 Aug 2019
Posts: 7
Location: Reunion Island

PostPosted: Thu May 14, 2020 1:52 am    Post subject: Korg SV-1, bulb lights on but not front pannel ! Reply with quote

Hello,

I was given a Korg SV-1 73, first generation.

When I run it, only the bulb lights on.

I've verified the PSU, and it gives me the good tensions (+5V, -15 V, + 15 V)

I've verified the tensions on the front panel and I have +3.52 V !

I've verified the tension on IC14 and I have, also, the good voltage !

I've read all questions in this forum but I've not found any answers !

I've tried to plug on a computer but the SV-1 is not recognized.


Have you an idea about this issue ?

Thanks a lot for your ideas,

Have a nice day,



[/b]
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voip
Platinum Member


Joined: 27 Nov 2014
Posts: 2452

PostPosted: Thu May 14, 2020 12:08 pm    Post subject: Reply with quote

There is very little info to go on.

What is the history of this keyboard? Has it been dropped or shows any sign of abuse? Has it been stored in a warm, dry environment? The weather on Reunion can be quite damp in the winter, which is not good for electronics if stored in a shed or garage.

What are the voltages on all of the pins on IC14 on the main board? Not just the supply voltage.

Is there any sign of electrolytic capacitor rot? Look for swollen tops of the capacitor, or leakage from the base of the capacitor.

Have you tried the restore to factory procedure?
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Musella



Joined: 08 Aug 2019
Posts: 7
Location: Reunion Island

PostPosted: Thu May 14, 2020 2:45 pm    Post subject: Reply with quote

Hello, thanks for your answer.

On the IC 14, the voltage is 3.24 on 3 of 4 pins.

For restore routine, I need the front panel is working, no ?
And I have no light, no buttons in working condition !!!

I've connected it with usb on a pc, but Windows cannot link it with drivers.
Windows see the sv1 but cannot accept it !

For history, it was put on a table and forbidden. Not in an warm site. No corrosion !

Have you a routine to reset it without usb or front panel ?

I have tested all capacitors on PSU and Audio bord.
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voip
Platinum Member


Joined: 27 Nov 2014
Posts: 2452

PostPosted: Thu May 14, 2020 3:33 pm    Post subject: Reply with quote

The factory restore is performed from a power-off condition, so it is possible there may be sufficient circuit functionality for an early-stage boot process low-level button detect routine to run, that checks for the FUNCTION button being pressed, and then runs a routine to restore the operating system. Many Korg keyboards have some means of restoring the operating system, usually from a backup area of ROM.
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Musella



Joined: 08 Aug 2019
Posts: 7
Location: Reunion Island

PostPosted: Thu May 14, 2020 3:51 pm    Post subject: Reply with quote

Thanks for the answer.

The Function button is not working !

I've tested but nothing happens !

The hard reset is on the main board. Near the ic14 (the pin 2 of ic14 is the reset) but even this, not working.
Yesterday, I succeed and the sv1was working for 20 minutes. I think the front panel has an issue. The sv1 needs the both front panels to boot.
All wires were verified.
On front panel there is a fusible (fusible1). It's OK !

I don't know where to search...

The Mx1 seems to be OK because it staryed Yesterday.

Perhaps the I2C protocol cannot run !
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voip
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Joined: 27 Nov 2014
Posts: 2452

PostPosted: Thu May 14, 2020 4:02 pm    Post subject: Reply with quote

Is the SD card slot empty?
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Musella



Joined: 08 Aug 2019
Posts: 7
Location: Reunion Island

PostPosted: Thu May 14, 2020 4:12 pm    Post subject: Reply with quote

I have not seen any SD card slot !
It's the SV-1 73 first generation. It's a red one !
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voip
Platinum Member


Joined: 27 Nov 2014
Posts: 2452

PostPosted: Thu May 14, 2020 5:05 pm    Post subject: Reply with quote

OK. So there may possibly be an intermittent connection somewhere. Either in a board interconnect (the wire or connectors) or a dry joint between component and solder pad, or a broken PCB track. It may be hard to find. Hopefully you are familiar with finding poor contacts in circuits.

As an example, I found an issue with a USB power bank the other day. Only one particular USB-C lead would charge it. None of the other leads that were tried would pass charge. It took very close examination with a microscope to find the solder hadn't flowed on the power bank PCB to one of the pins at the back of the USB-C connector inside the power bank. The USB lead that worked was slightly out of position inside the connector, just enough to push the pin inside the power bank to make contact.

Good luck.
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Musella



Joined: 08 Aug 2019
Posts: 7
Location: Reunion Island

PostPosted: Fri May 15, 2020 12:44 am    Post subject: Reply with quote

Thanks for your ideas.

I'm going to verify all solder joints !

Connectors were verified and there's no problem with them.
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