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weird amp hum
weird amp hum
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Old 20th June 2019, 12:39 AM   #11
stephen_keller is offline stephen_keller  United States
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Location: Portland, OR
Apparently this amp is also sold under the Yiwei brand name. I doubt contacting any of the folks will yield a schematic, but figured I'd pass along what I found:

China Guitar Amplifier (GA-45R) - China Guitar Amplifier, Bass Amplifier

YueSen Musical Instrument Factory China --Products

Quality GUITAR AMPLIFIERS GA-45R of 34731702

It is also available under the brand name "E-WAVE." It is possible various forum searches might turn up something more.


Last edited by stephen_keller; 20th June 2019 at 12:47 AM.
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Old 20th June 2019, 06:58 PM   #12
Gnobuddy is offline Gnobuddy  Canada
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An amp made in heaven, literally (See attachment, from one of Stephen's links.) I never thought I'd see that!

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File Type: jpg Heavenly_Amp.jpg (83.9 KB, 49 views)
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Old 26th June 2019, 09:40 AM   #13
jakeblues is offline jakeblues
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Default PCB picture

So here's the pic of the PCB. I only photographed to upper side, maybe that helps to identify similar/identical prodcuts.



Thanks for all the other input. And yes, that's the one I got for next to nothing.

I'll report back if I got any further...

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Old 26th June 2019, 10:47 PM   #14
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by jakeblues View Post
So here's the pic of the PCB.
I notice some of the electrolytic capacitors are lying almost on their sides, instead of standing vertical.

They may simply have been installed like this at the factory, in which case there should be no problem.

But if they were installed vertically and later pushed over by some clumsy person working inside the amp, there is a chance that one of the wire leads underneath the capacitor broke. Depending on the function of that capacitor in the circuit, this could cause hum (if it is a filter cap that normally removes hum from the power supply lines.)

So there's a small chance that your mysterious clean-channel hum is caused by one of these capacitors having been damaged by mis-handling.

I suggest carefully looking at the leads under each of the capacitors that is bent heavily to one side. Don't move the capacitor unless you have to, as you don't want to break leads yourself! Just check and verify that there are two unbroken wires running from each capacitor into the little holes in the PCB.

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Old 26th June 2019, 11:32 PM   #15
wiseoldtech is offline wiseoldtech  United States
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From the looks of that board, it's been hastily populated (aka sloppy job), likely in some sweatshop.
God only knows what issues are lurking there.
I've come across things like this before, and it's a headache.
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Old 27th June 2019, 01:23 AM   #16
Gnobuddy is offline Gnobuddy  Canada
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Originally Posted by wiseoldtech View Post
...sloppy job...
Remarkably so! Caps at angles, diodes sticking way off the board, leads at weird angles, it's all there!

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