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Pero68
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Reged: 08/22/06
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Help me to repair 1943 board
#369651 - 09/13/17 12:04 AM Attachment: 1943 potenciometar (2).JPG 322 KB (0 downloads)


Hello,

Sound in game is too loud and I cannot regulate volume.
Only one potentiometer is on the board. I think it is for the regulation of loudness, but when I rotate potentiometer, nothing happens. Only thing written on the potentiometer is MIKO TPE without any information about its resistance.
Does anybody know something about that potentiometer?

[ATTACHED IMAGE - CLICK FOR FULL SIZE]

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MrWidget
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Reged: 09/11/17
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Re: Help me to repair 1943 board new [Re: Pero68]
#369686 - 09/14/17 12:38 PM


Hi Pero68,
My first thought is; if this potentiometer is to regulate the volume, then it may have cracked or burnt open-circuit due to its age. Get a multimeter set to resistance on the pins on the back. There are usually three pins, the outer pins are across the whole resistance and the middle one is the variable one. Check you are getting a variable resistance. (Often two pins are connected together, so you will only get a variable result from one pair of pins.) I will have a hunt to see if I have a circuit diagram for this board.



MrWidget
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Reged: 09/11/17
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Re: Help me to repair 1943 board- circuit diagram new [Re: MrWidget]
#369688 - 09/14/17 01:00 PM Attachment: 1943 sound out.jpg 347 KB (0 downloads)


This is the circuit diagram for the sound output of 1943 board I have on file. I've put a big arrow pointing to the variable resistor I would expect to be volume control. Hope it helps..

[ATTACHED IMAGE - CLICK FOR FULL SIZE]

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Pero68
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Reged: 08/22/06
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Re: Help me to repair 1943 board new [Re: MrWidget]
#369695 - 09/14/17 08:28 PM


Hi MRWidget.
Resistance between pins 1-3 is 525-1836, pins 1-2 648-1751, and 2-3 1415 ohms.
Looks like potentiometer works. But, I do not know is this normal values for this potentiometer?
Today I try to clean up potentiometer with 96% alcohol, and nothing is better. Sound is too loud. Other boards works fine.



MrWidget
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Re: Help me to repair 1943 board new [Re: Pero68]
#369765 - 09/18/17 01:11 AM


The values are not unusual, but I don't know exact values either. With your issue I would identify the sound area of the board and inspect it for broken tracks, dry joints, resistors that read 0 ohms or open circuit, capacitors that are short circuit. The max volume means that a part of the circuit or a component is either open circuit or short circuit when it shouldn't be. Something is allowing the amplifier section to stay at maximum gain. Dry joints are common on old boards. Definitely use a magnify glass to spot tiny cracks or not perfectly soldered legs. Post again if you are still at a loss. M


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