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Technics Organ GN3 - Spare part for Tone Generator

I have a GN3 with a faulty tone generator detected. Would appreciate if anyone could assist me in getting a spare parts for tone generator. The main board is QJBG2001. Part No is QSIGU3C04732 MODEL GN5,3

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Technics Organ GN3 - Spare part for Tone Generator

scyv

scyv
Malaysia

Total Posts: 2
Joined: March 29, 2017

I have a GN3 with a faulty tone generator detected. Would appreciate if anyone could assist me in getting a spare parts for tone generator. The main board is QJBG2001. Part No is QSIGU3C04732 MODEL GN5,3

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Posted on March 29, 2017 at 2:59 AM
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3 Replies

davetutt

davetutt
United Kingdom

Total Posts: 166
Joined: January 12, 2015

Re: Technics Organ GN3 - Spare part for Tone Generator

Unless you can find a supplier with a complete scrap board it is unlikely you will have any luck with that sort of repair. I repair nearly all the Technics boards at component level as there haven't really been any spares for at least 10 years. Most faults on these boards are due to failure of the switch mode power supply unit that is part of design and also a part that is really becoming a bit of a liability as it is always this that causes the initial issue and then can subsequently cause other problems. Fortunately the repair isn't impossible. But you do need skills with surface mount components and an understanding of electronic hardware. At the same time it is advisable to upgrade the cooling on the board to make it more reliable. I have found few boards that need anything more than the repair of this circuit and once done everything else comes alive. If you have either the skills with a soldering iron yourself or have a good local repair engineer then by all means drop me a line and I will run through the bits that need replacing.

Regards

Dave Tutt

Posted on April 23, 2017 at 11:17 PM

scyv

scyv
Malaysia

Total Posts: 2
Joined: March 29, 2017

Re: Technics Organ GN3 - Spare part for Tone Generator

Dear Mr. Dave Tutt,

Thanks a lot for your reply. I have finally found an engineer who can assist me in circuit board and soldering. Therefore, I would highly appreciate if you could guide us on the parts that need to be replace so that we can start sourcing for it.

Thanks again and I really hope that one day my organ will come alive again!

Have a great day!
Best Regards,
Silvia

Posted on May 19, 2017 at 12:50 AM

davetutt

davetutt
United Kingdom

Total Posts: 166
Joined: January 12, 2015

Re: Technics Organ GN3 - Spare part for Tone Generator

Hello

There are several parts you need to find. You are looking for the main switching regulator that is on the main voice board. I have added a picture which I hope you can see. The parts most likely to fail are:

output 1000uf 6 volt capacitor (use a 105 C version) which I think is C551 just to the rear of the transistor on the heat sink.
the output chopper transistor on the heatsink TR5
any of the associated 2sa1815 to92 type transistors
c557 which is the small capacitor that sits next to the comparator and smooths the comparator reference voltage
and the tiny surface mount comparator which is a 393 series dual type
you should also replace the 47uf 63v input capacitor

Depending on what happened when things stopped working you may find the feed resistor on the audio output board is open circuit. This feeds around 40 volts to the chopper circuit and if it is open circuit you will get the same results again when you try to power the organ. The resistor is a 2.5watt wire wound 6.8 ohm resistor that protects the main board should the chopper fail.

This should give you a start for your repair. I would be very surprised if once these have been replaced if your organ doesn't start up again as normal!

Regards

Dave

Attachments: IMGP3779.JPG
Posted on May 19, 2017 at 12:43 PM