I am working on this for a friend. The volume pot definitely is bad but sourcing a new one is not working (loudness tap) and wanted to ask for opinions on what I see may be options:
Schematic attached for clarity.
The volume pot is a 100KBX2, I have not pulled it yet but it should be linear taper and of course it has a loudness (contour) tap. There is a 6.8K resistor on the tap to ground with the contour off, add a capacitor in series with it on. The loudness switch is not a requirement.
Possible options:
1) Use a 100KAX2 log taper pot and remove the loudness circuit. Just removing the loudness circuit with a linear pot will result in too much signal to quickly, with a log taper that may not be the case?
2) Use a linear taper (or log taper) pot and add a resistor from the input to ground to keep the signal level attenuated. Maybe 6.8K + the resistance form the loudness tap to the input.
Schematic attached for clarity.
The volume pot is a 100KBX2, I have not pulled it yet but it should be linear taper and of course it has a loudness (contour) tap. There is a 6.8K resistor on the tap to ground with the contour off, add a capacitor in series with it on. The loudness switch is not a requirement.
Possible options:
1) Use a 100KAX2 log taper pot and remove the loudness circuit. Just removing the loudness circuit with a linear pot will result in too much signal to quickly, with a log taper that may not be the case?
2) Use a linear taper (or log taper) pot and add a resistor from the input to ground to keep the signal level attenuated. Maybe 6.8K + the resistance form the loudness tap to the input.
Have you tried cleaning the pot with deOxit? It seldom fails.
Much better to use a good stereo log volume pot with no loudness tap.
If he's the kind who always has the loudness on, just tell him to turn up the bass instead.
And it's adjustable, too.
Much better to use a good stereo log volume pot with no loudness tap.
If he's the kind who always has the loudness on, just tell him to turn up the bass instead.
And it's adjustable, too.
3 times, and from what I have found on searching this is not uncommon for this model. I have replaced bad volume pots before and disabled loudness circuitry. But this is the first one that has a resistor shunting signal to ground with the loudness turned off.
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It may be a linear pot, with the law faking resistor and tap required for proper operation.
This approach does improve low level tracking, compared to most stereo log pots.
This approach does improve low level tracking, compared to most stereo log pots.
