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CoastalBug Samba Member

Joined: June 15, 2025 Posts: 141 Location: TX Gulf Coast
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Posted: Tue Aug 05, 2025 1:42 am Post subject: Sapphire Radio Potentiometer Connections? |
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I'm doing a little bluetooth project using a Sapphire XV radio that I've gutted. I'm reusing the original volume/on/off switch as the main power switch. I believe only the back of the potentiometer is the on/off. If I'm correct the black wire at the bottom would be ground, the red would be 12v positive input, and the white would be the positive output to the rest of the internals. Is that correct? Anyone have any idea?
_________________ Chris - 1968 Beetle Sedan, a book, and a lot of determination. |
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sctbrd Samba Member

Joined: May 06, 2013 Posts: 312 Location: Moravia, Czech Republic
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Posted: Tue Aug 05, 2025 4:20 am Post subject: Re: Sapphire Radio Potentiometer Connections? |
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looks sound to me, looking at the wiring diagram. check with an ohmmeter from red to black and operate the switch.
the blue cap in your photo is C23 at the switch outlet:
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CoastalBug Samba Member

Joined: June 15, 2025 Posts: 141 Location: TX Gulf Coast
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Posted: Fri Aug 08, 2025 6:17 pm Post subject: Re: Sapphire Radio Potentiometer Connections? |
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ok. I've got my ohm meter.
With the meter on continuity, and the switch off, I get a tone and 000 on the meter with black and red wires. I get .939 with black and white wires.
With the switch turned on, black and red give me .577, and black and white give me .940.
There's also a yellow wire on the back, but I can't seem to figure out exactly what that is.
Any of you electronics guys have any clue? _________________ Chris - 1968 Beetle Sedan, a book, and a lot of determination. |
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CoastalBug Samba Member

Joined: June 15, 2025 Posts: 141 Location: TX Gulf Coast
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Posted: Fri Aug 08, 2025 6:25 pm Post subject: Re: Sapphire Radio Potentiometer Connections? |
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So now that I'm thinking about it. The white may be the incoming power from the battery, black would be the ground, and red would be the switched power going out to the BT board and incandescent light.
I think that is correct. _________________ Chris - 1968 Beetle Sedan, a book, and a lot of determination.
Last edited by CoastalBug on Fri Aug 08, 2025 6:49 pm; edited 1 time in total |
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CoastalBug Samba Member

Joined: June 15, 2025 Posts: 141 Location: TX Gulf Coast
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Posted: Fri Aug 08, 2025 6:46 pm Post subject: Re: Sapphire Radio Potentiometer Connections? |
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Disregard, I just answered my own question. If I turn the knob up with the switch on, I can increase and decrease the ohms which would signify volume power. _________________ Chris - 1968 Beetle Sedan, a book, and a lot of determination. |
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CoastalBug Samba Member

Joined: June 15, 2025 Posts: 141 Location: TX Gulf Coast
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Posted: Fri Aug 15, 2025 8:51 pm Post subject: Re: Sapphire Radio Potentiometer Connections? |
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How would I keep the capacitor in the loop if I wanted to continue to use it? I was able to get my project up and running, but without the capacitor, I have to make sure the knob is all the way up so full power is delivered to the board. Any miniscule reduction turns the board off. _________________ Chris - 1968 Beetle Sedan, a book, and a lot of determination. |
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runamoc  Samba Member

Joined: June 19, 2006 Posts: 6443 Location: 37.5N 77.1W
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Posted: Sat Aug 16, 2025 9:38 am Post subject: Re: Sapphire Radio Potentiometer Connections? |
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| keep the capacitor |
A capacitor can do different things with DC voltage. It can 'pass' AC and block DC. That the reason capacitors are used for noise suppression, it passes the AC to ground taking out the 'humm'. They can also 'flatten' out varying DC voltage. Leaving the capacitor connected maybe just be lowering the total resistance. The potentiometer is now a rheostat. Adding a parallel resistor will decrease the total resistance and may give you a wider range better than using a capacitor.
https://startingelectronics.org/resistors-in-parallel/#did-you-know-about-resistors-in-parallel _________________ Daily driver: '69 Baja owned 45 yrs - Plan B: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs- '80 Rabbit Diesel
VW Wiring = It's just wires |
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