TL;DR near end
Was blessed enough to come across a Yamaha DSP-A3090 in nice cosmetic shape for $40 CAD at a thrift store. I bought it untested, less it powers on.
It has / had two issues, pot for Main Front had right channel spoiled. Basically "random" resistance / volume level. All other channels seemed fine.
Other issue is pretty small, the mechanical action of the power switch is spoiled, however the switch still works. meh with that issue.
So managed to disassemble what must be the longest chain of pot gangs (two six pin 2 gang pots, and a 12 pin two gang pot) Being a mix of multi channel and digital, I've never seen such a thing lol.
Issue was the volume knob had been forced passed the "stop" (in first pot / for front mains, on right channel" and completely chewed up the right channel gang.
I tried new pots of another manufacture as replacement parts source...while so close, there was slight difference and could not utilize said parts.
However that experience (am new to this stuff) gave me confidence the pots, or entire sting of them could be "rebuilt" if I had the proper era Alps pots.
So picked up a Yamaha RSX-850, while not digital is multi channel / prologic. Having not first verified was very happy to see exact same volume mechanism in the RSX-850, well nearly the same, not a direct replacement but can harvest it for the rebuild of the original.
Thankfully the removal of the volume mechanism from the RSX-850 was much easier than with the DSP-A3090 as it was on it's own board and had long leads to various parts in the amp, was able to de-solder without much trouble.
rebuild went well, less the locking in the volume shaft that passes though all the pots, however a small detail imo.
Resistance comparatives where decent I think, no more than a couple of kohms difference amongst the gangs. success! 😀
TL;DR - So onto the question lol
It's been so long since I've had volume control via potentiometer that am not sure if the "taper" is proper.
at just "3/8ths volume" it is as though is zero db for this amp. it is loud! only comparative I have are digital volume controls and yea, I doubt are comparable at all.
So does that seem typical for potentiometer controlled volume? It seems like never would the volume be passed 1/2, the volume gain in the last half must be nill.
Am certain the pots are the same, that is measured resistance, compared replacement to original. both same model of alps pot, both 100k, both start at around 87kohm.
ETA- I've not checked DC on speaker output, nor checked / adjusted bias. internals cleaner than expected for avr of this era. Audio seems fine, however not yet measured with signal generator & scope.
Was blessed enough to come across a Yamaha DSP-A3090 in nice cosmetic shape for $40 CAD at a thrift store. I bought it untested, less it powers on.
It has / had two issues, pot for Main Front had right channel spoiled. Basically "random" resistance / volume level. All other channels seemed fine.
Other issue is pretty small, the mechanical action of the power switch is spoiled, however the switch still works. meh with that issue.
So managed to disassemble what must be the longest chain of pot gangs (two six pin 2 gang pots, and a 12 pin two gang pot) Being a mix of multi channel and digital, I've never seen such a thing lol.
Issue was the volume knob had been forced passed the "stop" (in first pot / for front mains, on right channel" and completely chewed up the right channel gang.
I tried new pots of another manufacture as replacement parts source...while so close, there was slight difference and could not utilize said parts.
However that experience (am new to this stuff) gave me confidence the pots, or entire sting of them could be "rebuilt" if I had the proper era Alps pots.
So picked up a Yamaha RSX-850, while not digital is multi channel / prologic. Having not first verified was very happy to see exact same volume mechanism in the RSX-850, well nearly the same, not a direct replacement but can harvest it for the rebuild of the original.
Thankfully the removal of the volume mechanism from the RSX-850 was much easier than with the DSP-A3090 as it was on it's own board and had long leads to various parts in the amp, was able to de-solder without much trouble.
rebuild went well, less the locking in the volume shaft that passes though all the pots, however a small detail imo.
Resistance comparatives where decent I think, no more than a couple of kohms difference amongst the gangs. success! 😀
TL;DR - So onto the question lol
It's been so long since I've had volume control via potentiometer that am not sure if the "taper" is proper.
at just "3/8ths volume" it is as though is zero db for this amp. it is loud! only comparative I have are digital volume controls and yea, I doubt are comparable at all.
So does that seem typical for potentiometer controlled volume? It seems like never would the volume be passed 1/2, the volume gain in the last half must be nill.
Am certain the pots are the same, that is measured resistance, compared replacement to original. both same model of alps pot, both 100k, both start at around 87kohm.
ETA- I've not checked DC on speaker output, nor checked / adjusted bias. internals cleaner than expected for avr of this era. Audio seems fine, however not yet measured with signal generator & scope.
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