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Finding and fixing a power surge failure

 
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yena



Joined: 07 Nov 2017
Posts: 5

PostPosted: Tue Nov 07, 2017 9:15 am    Post subject: Finding and fixing a power surge failure Reply with quote

A lightning strike caused a power surge that killed my Triton Extreme, and would really like to fix it if possible. When I turn it on the screen lights up for a second, but then it goes dark and everything else (LEDs, sound) is dead.

I have opened the body and checked the main ceramic fuse. It seems to be fine. I have checked the input cabling into the power mains board and it has mains power. A visual inspection of the visible boards don't show any signs of loose cables, scorch marks or bad capacitors.

I would like to see if the power from the power board into the the rest of the system but I have no schematics and don't know what to look for or where to test. Does anyone have experience with these problems or access to technical manuals? Any advice would be greatly appreciated. I don't want to see such a great instrument end up in a garbage pit.
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voip
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Joined: 27 Nov 2014
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PostPosted: Tue Nov 07, 2017 9:54 pm    Post subject: Reply with quote

How close was the lightning strike?
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yena



Joined: 07 Nov 2017
Posts: 5

PostPosted: Wed Nov 08, 2017 1:37 am    Post subject: Reply with quote

voip wrote:
How close was the lightning strike?

Really close, perhaps less than 100 meters/yards away. The power surge also killed a desktop computer and everything connected to it by USB (keyboard, mouse, printer). The Triton Extreme at least shows some signs of life (the display briefly lights up when I turn it on).
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voip
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PostPosted: Wed Nov 08, 2017 8:12 pm    Post subject: Reply with quote

100m is definitely close. Was anything else in the room/flat/house damaged? Was the keyboard connected to other things, such as audio outs to a mixer, amplifier, or via MIDI or USB? Any of those connections may have contributed to the surge current flows and the damage caused. The main path for surges from lightning strikes is likely to be the mains power cable so the power supply inside the keyboard generally takes the biggest hit. This can be checked for correct output, if you have a multimeter to hand, set to measure voltage.

The main power supply has four output connectors. A 3-pin, 4-pin and two 5-pin connectors. The 3-pin is commoned with the 4-pin and should have 5V between the outside pins. The two 5-pin connectors are commoned, and carry -15V on pin 1, +15V on pin 3, both referenced to analogue ground on pin 2, and +5V on pin 5, referenced to digital ground on pin 4.

If any of these supply voltages is significantly different from nominal, then the power supply will need to be replaced/repaired.

.
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yena



Joined: 07 Nov 2017
Posts: 5

PostPosted: Wed Nov 08, 2017 11:34 pm    Post subject: Reply with quote

voip wrote:
Was the keyboard connected to other things, such as audio outs to a mixer, amplifier, or via MIDI or USB?


At the time only the power cable was connected to the synthesizer.

voip wrote:

The main power supply has four output connectors. A 3-pin, 4-pin and two 5-pin connectors. The 3-pin is commoned with the 4-pin and should have 5V between the outside pins. The two 5-pin connectors are commoned, and carry -15V on pin 1, +15V on pin 3, both referenced to analogue ground on pin 2, and +5V on pin 5, referenced to digital ground on pin 4.


Thanks for the advice. Actually I have 3-pin, 4-pin and 2 7-pin connectors, but I have measured on pin 4 and 5 on the 7-pin connector. Before making measurements I disconnected all the flat cables expect the power main input.

The 3-pin and 4-pin connectors show the expected 5V, but the 5-pin (actually 7-pin) connectors are bad. The digital line is 0.86V instead of 5V, and the analog is +1.7, -3.5V instead of +-15V. It also seems that the voltage is unstable; sometimes the voltage seems start dropping while I measure. It doesn't seem to be reproducible though.

Obviously the power board is damaged. Any idea of how to fix it, get it serviced, or get a new one?
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voip
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Joined: 27 Nov 2014
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PostPosted: Thu Nov 09, 2017 9:13 am    Post subject: Reply with quote

Interesting. The 5V line on the larger connectors comes from the same supply as the 3-pin connector so, either the printed circuit track is damaged or the correct ground is not being used for the measurement reference point. It would be worth looking at the underside of of the PSU board for possible damage.

For a replacement PSU you could try these folks:

http://korgparts.net/product/power-supply-board/

Repairing switched mode power supplies requires an understanding of how they work.

.
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yena



Joined: 07 Nov 2017
Posts: 5

PostPosted: Thu Nov 09, 2017 8:40 pm    Post subject: Reply with quote

voip wrote:
Interesting. The 5V line on the larger connectors comes from the same supply as the 3-pin connector so, either the printed circuit track is damaged or the correct ground is not being used for the measurement reference point. It would be worth looking at the underside of of the PSU board for possible damage.

I took out the board and I see visible damage around CN2 on the back (looks burnt). I don't think I can fix this so I need to order a replacement board and hope that this is the only problem. Thanks for your advice.
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voip
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PostPosted: Thu Nov 09, 2017 11:07 pm    Post subject: Reply with quote

The trouble with lightning surge damage is that it can often be more extensive than first appears. There is no guarantee that replacing the PSU will fix the problem. Good luck. Was the keyboard insured?

.
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yena



Joined: 07 Nov 2017
Posts: 5

PostPosted: Thu Nov 09, 2017 11:14 pm    Post subject: Reply with quote

voip wrote:
The trouble with lightning surge damage is that it can often be more extensive than first appears. There is no guarantee that replacing the PSU will fix the problem. Good luck. Was the keyboard insured?
.


I understand that the there might be more problems but I think it is worth a try. I'm claiming the keyboard on the home and contents insurance but it is being processed so I don't know the outcome yet. Even if I get some money it would be hard to get another like it - I see that the second hand prices for Triton Extreme have increased quite a bit since I bought mine six years ago.
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