Synsonics guitar amp help

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Synsonics guitar amp help

Postby fortj3 » 28 Oct 2017, 17:36

I have a Korean made Synsonics 12 volt DC solid state guitar practice amp.
I know nothing of the ownership or usage history. I got it cheap with some cables, strings, and a stompbox.
Anyway, when I plug it in and turn it on it hums.
However, the power-on LED does not come on.
Also, when I plug my guitar into it, and play, no sound comes out.

I am in need of diagnostic/repair advice.
Any help is greatly appreciated.

If this post is in the wrong place, I apologize.
I haven't been a member here for very long and don't really know my way around this forum.
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Re: Synsonics guitar amp help

Postby fortj3 » 28 Oct 2017, 18:57

OK. i have found an issue with my 12 volt power supply.

I don't have another 12V wall wart.
I do have a PC power supply.
Only thing is, the output voltages I'm getting are 5 VDC (correct), 10.7 VDC :scratch: , and 14.5 VDC :scratch: .
It should output 5 VDC at the red and black wires, and 12 VDC at the yellow and black wires.
The 14.5 VDC is output at the orange and blue wires. That would work for a battery maintainer for my motorcycles, but I'm not sure if it's going to cause problems with the amp.

I wonder if I can safely run the amp off of 10.7 VDC or 14.5 VDC?
I don't want to let the smoke out of any of the circuits, because it's hell to try to stuff it back in.

I'm not new to electrical or electronic troubleshooting/soldering/repairing.
HOWEVER, I am very rusty. I will be relearning a lot of things along the way.

I plan on building some stompboxes, because I'm cheap and stompboxes aren't.
Plus, it's fun to build things.
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Re: Synsonics guitar amp help

Postby deltafred » 29 Oct 2017, 11:28

Look up the datasheet for the output chip and you will have almost everything you need to know, including half of the schematic.

14.5v may be ok but PC power supplies are not ideal for powering low power circuits because they often need to supply a minimum current, usually on the +5v output, to operate correctly.
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Re: Synsonics guitar amp help

Postby fortj3 » 31 Oct 2017, 00:21

How do I tell which chip is the output chip?

BTW, the PC power supply is a no-go.
I'll figure something else out.
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Re: Synsonics guitar amp help

Postby deltafred » 31 Oct 2017, 10:54

fortj3 wrote:How do I tell which chip is the output chip?

BTW, the PC power supply is a no-go.
I'll figure something else out.

If it is a GA-150 or similar it's the one attached to the aluminium heatsink in the photo below on the right hand side.

SynsonicsGA150guts.jpg.jpg


Photo from https://reverb.com/uk/item/4822613-syns ... cuit-board
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