thisafternoon wrote:
I've replaced the 1, 1, 1 and 10uF caps with 30 yrs old caps I had lying around.
Finally I have some sound. I might even say it's promising...
But.. the Tone is not doing anything at all and the Sustain is only coming to life at the very end near 3 to 5 o'clock. Volume potmeter seems to work fine.
Before I get some new caps, is this likely to cause this issue? And will some new caps probably result in a working Tone and Sustain?
Not sure those old caps would cause your current problems, but I would replace them with new caps in any case. Electrolytics don't last forever and are generally recommended for replacement after 10 - 15 years of use. If you're sure that they've seen little or no use, they might be OK, but I wouldn't chance it myself.
thisafternoon wrote:
One thing I did notice during building: I received 3 potmeters labelled with an A....Not two with an A and one with a B as indicated in the Beaver Instructions:
Are they the same? Or did I perhaps got one a wrong potmeter and could this have something to do with my problem?
While the B pot (or potentiometer; I haven't seen them called "potmeters", but maybe you're onto something new here!
) is not exactly the same as the A pots, the difference between them is such that it wouldn't cause the problem you're seeing.
The letter in front of the max. resistance rating of the pot denotes its TAPER, i.e. the speed at which the resistance changes as the knob is turned. A pots have an audio taper (also referred to as a logarithmic taper), so named because they respond in a manner analogous to how the human ear perceives volume change. The resistance changes slowly at the beginning of the pot sweep and increases in rate of change as the pot is turned up. At the midpoint of it's sweep, most audio taper pots are only at about 15 - 20% of their maximum resistance change.
B pots have a linear taper; for example, at their sweep midpoint, they will be very close to half of their rated resistance change. So compared to an audio taper pot, they change more quickly to start with, but then more slowly in the latter part of their sweep.
What's important to realize is that for A and B taper pots of the same resistance rating, they will have the
same resistance values (within manufacturing tolerance) at either end of their sweeps. The difference is how quickly they change that resistance in between the two extremes.
You can read more on this subject here:
http://www.resistorguide.com/potentiometer-taper/BTW, I still believe that the most likely cause of your issues is solder joint quality. I still see a lot of blobby or irregularly shaped solder joints, and a number of cases where I don't see solder "peeking through" the eyelets on the component side of the PCB. This latter condition is typical of inadequate solder flow, which frequently results in incomplete electrical contact. And since you're reporting poor pot response for the Tone and Sustain controls, I'd definitely be re-flowing the wire connections on those, both at the pot lugs and PCB connections.
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