TC Electronics G-Major Power supply failure - diyAudio
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Old 31st July 2013, 07:11 AM   #1
nuryev is offline nuryev  Australia
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Default TC Electronics G-Major Power supply failure

Hi

I have a TC Electronics G-Major guitar effects processor with a failed power supply. It seems this is a common issue and was wondering if any diyAudio members have had any similar experiences and resolved them with a diy fix.

The manufacturers refer to local suppliers who have a 300%mark up on a replacement psu and I am wondering if it is worth the time and effort trouble shooting the psu and fixing if it is repairable.

Any advice or direction is appreciated.

Thanks
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Old 31st July 2013, 04:24 PM   #2
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I have been working on a new PSU (with some help from members on here) for my Soundcraft mixer. Maybe I can help.


What are the requirements for the PSU? (voltage and amperage)
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Old 1st August 2013, 07:16 AM   #3
nuryev is offline nuryev  Australia
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Hi Thump LUMP
Thanks for positive the response.
I have no access to service manuals or schematics for the PSU. But the following information is printed on the PSU pcb.

1)The Board is JKS020Q1 Rev: D.
2)Connections from PSU to PCB indicate
that the Primary voltage is for Australian use (230v)
secondary voltages are: +3V, +5v as well as +15V 0v -15V.

Hope this information helps. I will upload some images of the PSU this evening.
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Old 1st August 2013, 08:00 AM   #4
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There are known issues with both power supplies. If you let me have the model number of the Soundcraft, I may be able to help. As for the G Major, it is discontinued but the issues should be easily resolved as long as the board is OK.
Soundcraft suffer from regulator issues.
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Old 1st August 2013, 08:11 AM   #5
nuryev is offline nuryev  Australia
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Thanks for the encouraging comment but I am not sure of what you mean re:
...both power supplies? are there two psus in the G-Major?
the numbers I provided :The Board is JKS020Q1 Rev: D. were off the psu board close to the Mains power connector. I will upload pics later this evening.
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Old 1st August 2013, 09:09 AM   #6
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Sorry, my mistake. I was refering to both the G-Major and the Soundcraft desk.
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Old 1st August 2013, 10:29 AM   #7
nuryev is offline nuryev  Australia
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Default G-Major psu pics

I have attached some pics of the psu and look forward to any suggestions or starting points.
Thanks.
Attached Images
File Type: jpg PSU6.jpg (519.9 KB, 62 views)
File Type: jpg PSU5.jpg (496.3 KB, 59 views)
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Old 1st August 2013, 10:43 AM   #8
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I would check to see if it is dead or just tripping,
If dead, change the FET and blue capacitor next to it and check the resistor values in the primary side. BE CAREFUL as the main smoother may have 300volts on it!
If tripping check for short circuit secondary diodes and leaking secondary electrolytic capacitors. A shorted diode will cause it to trip.
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Old 1st August 2013, 10:54 AM   #9
nuryev is offline nuryev  Australia
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I have a DVM and can check.

Point the way - I am not technically trained and would appreciated directions - are you able to point out the parts or tell me which parts to test.
would I have to remove these from the board before testing?
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Old 1st August 2013, 11:03 AM   #10
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In that case, as you are not too sure, be very careful and first thing is to discharge the main capacitor the blue electrolytic next to the transformer.
When you are satisfied that it is safe to remove the board to allow access to the copper side, release the board to allow access to the copper side.
Check the secondary diodes for short circuits. If all OK, replace the FET power transistor and the blue small capacitor between the FET and transformer. Check the value of the resistors on the FET side. That is about it. Any more will require an isolating transformer and test gear with a lot of knowledge.
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