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Chip Amps Amplifiers based on integrated circuits

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Old 27th September 2020, 10:17 AM   #1
GooseyGander is offline GooseyGander  France
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Default Complete novice alert! *don't read if easily annoyed by stupid questions*

Hello all. I just recently decided during lockdown to learn some basic electronics. I then found I just had to build myself an amplifier of some kind. I then found this Instructable: https://www.instructables.com/id/Mak...ous-Amplifier/ I have copied it as far as I can but am now stuck. I have followed the original version but used a blank pcb used some other ideas from someone else who has made this (at the bottom of the website). Basically I am stuck as to where the connection goes to V+. Also what happens at the potentiometer and the front switch. Can anyone help? This is a pic of where I'm at, but I don't know if it will help:

Click the image to open in full size.
The two connectors in the centre of the pic are where the lines from pin 10 (V+in) and pin 1 (V+) come to. I don't know where these connect to tbh. Any help very gratefully received!
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Old 27th September 2020, 04:18 PM   #2
ctrlx is offline ctrlx  United Kingdom
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it appears the psu is on the same board as the amp, i would put the psu on its own board, then test it.


test the amp with batteries before running it from the psu.


after this you can sort out the input wiring.
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Old 27th September 2020, 05:03 PM   #3
jjasniew is offline jjasniew  United States
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Complete novice alert! *don't read if easily annoyed by stupid questions*
If rebuilding what you have is unsettling, you'll have to at least be able to partition it into sections conceptually. Maybe dont connect the amplifier V+ (pin 10) to the power supply V+ just yet. The two connectors were suggested by the original designer for a purpose...

Do you have any test equipment on hand? If you have a DMM, that would help you to assure the power supply part is working - before connecting it to the amplifier part.

The most feared result of first power-on is smoke/fire, or an audible "pop" - and that's it. If you have no test equipment (like a Variac... DMM...), you may have to build something to help you out. If you've nothing beyond the parts used to build the amplifier on hand, it's going to take some real creativity to limit the AC current going into your power supply portion, for first power-on debug. (something like a 110V, 15W lightbulb wired in series with the AC line to the power supply part)

"AC line" - I shudder to even suggest those words to a noob probably without an AC line isolation transformer. Be_Super_Careful when messing with the AC input part of your project. Uh, "Wife is calling" so I gotta go at this point. Good luck with your new amplifier build.
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Old 27th September 2020, 05:16 PM   #4
GooseyGander is offline GooseyGander  France
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Thanks so much for your replies. I have made a dim bulb tester (that works ��) so I can test it up to a point. My version is a mixture of the original one and the first person that made a version of it (bottom of Instructable site page) so this is probably where I’ve got confused (easily done). I have a multimeter but no other testing equipment. I think if I’d followed the original poster’s version with separate psu and amp, I’d be fine ��
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Old 27th September 2020, 06:27 PM   #5
jjasniew is offline jjasniew  United States
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Complete novice alert! *don't read if easily annoyed by stupid questions*
Great! So if the power supply section (even though it's on the same board) passes your "dim bulb" tester, you should be able to test it for its voltage value using your multimeter. You should know from the instructable what voltage to expect - and it should appear at the terminal for power supply V+ on your board.

I assume the power supply V-, or "ground", is also available on that connector as a separate terminal.
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Old 28th September 2020, 09:52 AM   #6
GooseyGander is offline GooseyGander  France
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The two pairs of connectors shown are (on left) from pin 1 (V+), one from chip on left, one from chip on right and the other pair are from pin 10 (V+ IN) L and R. The connection from both pin 4 (V-) is on the top right of board joining another ground wire. Does that make sense?

Last edited by GooseyGander; 28th September 2020 at 10:21 AM.
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Old 28th September 2020, 09:21 PM   #7
PRR is offline PRR  United States
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Complete novice alert! *don't read if easily annoyed by stupid questions*
> where the connection goes to V+.

It's not a stupid question. It is a very lame build instruction. About 90% right, which is enough to confuse. I think today's ??? is that the two power rails are called one thing on one drawing and another thing on another drawing. A builder with 2-3 builds done will probably figure this out. For a first-timer, this is not enough help.

Here's my mark-up.
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File Type: gif GooseyGander-1-42.gif (74.2 KB, 595 views)
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Old 30th September 2020, 01:28 PM   #8
GooseyGander is offline GooseyGander  France
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Well now I'm a bit more confused I have measured the voltage from my transformer and I'm getting 18v from the yellow and red wires. According to the data sheet for this transformer, the secondary coils should be red/yellow and blue/green, so this okay. But which pair do I twist together and connect to the rectifier? This is my transformer:Security Check
Thanks so much for the help so far
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Old 30th September 2020, 01:47 PM   #9
Mooly is offline Mooly  United Kingdom
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Complete novice alert! *don't read if easily annoyed by stupid questions*
If you connect yellow to blue and then measure the AC voltage from red to yellow/blue you should get 18 volts. Measure from red to green and you should see 36 volts.

If the last test gives near to zero volts then reverse the blue and green connections so that you measure 36 volts end to end. The centre joined connection then becomes the 0 in 18-0-18
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Old 30th September 2020, 02:27 PM   #10
GooseyGander is offline GooseyGander  France
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Okay. I've done as you suggested and when yellow/blue is connected to green I get 0v. When yellow/blue connect to red I get 20v. Red to green I get 0. So I tried yellow/green to blue, got 20v. Red/green to yellow, 20v. In no combination I tried could I get 36v
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