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Chipamp IC amp kits & PC boards from ChipAmp

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Old 20th February 2018, 10:18 PM   #61
scottjoplin is offline scottjoplin  Wales
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You're welcome. Disconnect the green wire. The signal flows from the source to the pot as you have done, from the middle pot terminal to the IN connection on the board, then to the amplifier chip. It returns from the SG terminal back to the pot "earth" terminal (as you have marked it) and then back to the source. This completes the circuit from source to amp.
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Old 22nd February 2018, 12:05 AM   #62
Hogwild is offline Hogwild  Canada
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Still humming and no sound. However, a couple of things I just noticed:

1. My fluorescent magnifying lamp was adding a ton of noise.
(Like I said, I'm new to this). I will have to remember to always unplug it before testing.

2. This was not actually one of the boards I was intending to test right now. But since it was working (measurement and sound-wise) before I attached the POT, I still need to know why it's not working now.

I desoldered the green wire from the POT. I left it soldered at the Chassis Ground end on the amp board.

There is still hum and no music. It sounds like ground hum, but I'm too new to know. I assume the green wire connected only to CHGND is not the problem?

Here are a few scope pics to show what the waveform looks like now. IIRC, this was with the POT turned about half way.


DS0015.BMP



DS0016.BMP

If I touch the POT or the output wire from the RCA audio source, the buzzing gets louder.

Last edited by Hogwild; 22nd February 2018 at 12:24 AM.
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Old 22nd February 2018, 09:27 AM   #63
scottjoplin is offline scottjoplin  Wales
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Can you post a photo of how you have it wired now?
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Old 22nd February 2018, 10:33 PM   #64
Hogwild is offline Hogwild  Canada
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Sorry, my battery died. Then, by the time I could charge it, I hadn't noticed that the cables had shifted slightly and I was once again running out of light. If you zoom in on the full size photo, you can see everything quite well.

So everything is still the way it was, excepted I desoldered the green wire from the POT end. It's still attached to the CHGND on the PCB end.

DSCN2472.jpg

Last edited by Hogwild; 22nd February 2018 at 10:42 PM.
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Old 22nd February 2018, 10:48 PM   #65
scottjoplin is offline scottjoplin  Wales
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Have another look at this picture https://qph.ec.quoracdn.net/main-qim...b9e6cdbbd063-c the grounds need to be connected to the pot as shown
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Old 22nd February 2018, 11:56 PM   #66
Hogwild is offline Hogwild  Canada
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I don't see the difference. AFAICT, that's exactly how I've connected things. What's the diff?
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Old 23rd February 2018, 09:02 AM   #67
scottjoplin is offline scottjoplin  Wales
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The grounds aren't connected to the "Earth" pin on the pot
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Old 23rd February 2018, 06:34 PM   #68
Hogwild is offline Hogwild  Canada
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Scott:

Which grounds? I need you to be more specific. Again, complete newbie. Please, spell it out for me.

Also, I started looking at breakout PCBs for POTs. The ones I'm seeing on ebay don't seem to have screwholes for mounting. Don't they usually have screwholes?

Last edited by Hogwild; 23rd February 2018 at 06:42 PM.
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Old 23rd February 2018, 06:38 PM   #69
scottjoplin is offline scottjoplin  Wales
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The signal ground/return. The screen of the input that you have connected to one of the white twisted wires, that joint should also go to the "earth" on the pot
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Old 23rd February 2018, 06:52 PM   #70
Hogwild is offline Hogwild  Canada
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The screen from the RCA input goes to the Input AND ground pins on the POT?
If so, should I just join them with another piece of wire? Will any similar primary wire work? Green?


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Originally Posted by scottjoplin View Post
The signal ground/return. The screen of the input that you have connected to one of the white twisted wires, that joint should also go to the "earth" on the pot
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