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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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20th May 2022, 9:34 am | #1 |
Diode
Join Date: May 2022
Location: Galati, Romania.
Posts: 4
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Sanyo RP1250 - volume control problem
Hello,
I have bought this nice design radio which has a problem: it plays very loud at minimum volume (right after the click of the pot). The volume turns even louder towards the end of its travel. I have tried with another potentiometer, the problem is the same. There are no PCB problems (missing the grounding of the potentiometer would have created a similar problem). I suppose the input signal is very high, but I have no idea how to turn it down. Last edited by Cobaltblue; 20th May 2022 at 9:38 am. Reason: circuit removed Rule B8 |
20th May 2022, 5:33 pm | #2 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,743
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Re: Sanyo RP1250 - volume control problem
An odd one. The circuit is pretty standard for a pocket set, so I would not expect this. First thoughts is the potentiometer or ground, but you have already eliminated this.
Is the sound clear, or does it distort? It would seem like a fault to me rather than a design issue, but you could always add a shunt resistor between the wiper of the pot and ground to reduce the overall level. |
20th May 2022, 5:36 pm | #3 |
Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,878
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Re: Sanyo RP1250 - volume control problem
I was wondering if there is a crack in the pcb effectively removing the connection to the bottom end of the volume control.
Cracks in PCBs are reasonably common as these little sets get dropped a lot. Cheers Mike T
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Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk |
20th May 2022, 6:19 pm | #4 |
Diode
Join Date: May 2022
Location: Galati, Romania.
Posts: 4
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Re: Sanyo RP1250 - volume control problem
Thank you for your replies.
I will check again for cracks, but the GND track of the potentiometer is covered with a thick layer of solder. Eventually I will add a resistor, but I was curious why this problem appeared. I don't think it came like this from the factory. |
28th May 2022, 11:11 am | #5 |
Diode
Join Date: May 2022
Location: Galati, Romania.
Posts: 4
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Re: Sanyo RP1250 - volume control problem
Eventually i will add a resistor because I can't figure it out. It might have been a problem from the AGC, but i can't figure where, the diode is ok. I don't think the capacitors or resistors have lost their values. The IF transformers have not been touched
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28th May 2022, 8:36 pm | #6 |
Hexode
Join Date: Nov 2003
Location: Linkoping, Sweden
Posts: 493
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Re: Sanyo RP1250 - volume control problem
On this radio the potentiometer is grounded to a short PCB track-only a couple of centimeters long.This ground track is in turn grounded to the rest of the radio through a wire.If this wire is badly soldered or cut off,you could very well get this problem.
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