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ARC SP-3 Volume Control Issue

ivandezande

ivandezande

AK Subscriber
Subscriber
EDIT: THIS IS THE PART ARC SELLS

www.parts-express.com

CLEARANCE ALPS 100KAX2 100K Ohm Audio Taper Stereo Potentiometer 6mm Shaft

ALPS 100KAX2 100K Ohm Audio Taper Stereo Potentiometer 6mm ShaftThe Alps 100KAX2 is a 100K ohm stereo potentiometer of the highest quality. The 6 mm straight shaft is 25 mm long, with M8 thru-hole mounting, hardware included. The body of the potentiometer is 1.073" W x 0.97" H x 0.93" D (27 x...
www.parts-express.com


Well I thought this one was working 100% but…the common issue got me.

The right channel doesn’t come in until you turn the volume to 1/3 or more. Then it gets way louder past 1/2!
I’ve tried DeOxit.

Do I just have to pay up to Audio Research or what have others done?
 
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Is there anything special about the volume control in these? Kinda just looks like a 2 section pot, I don't even see loudness taps or a power switch on it. Seems like you could just get a good quality pot of the proper value and sub it
 
gadget73 said:
Is there anything special about the volume control in these? Kinda just looks like a 2 section pot, I don't even see loudness taps or a power switch on it. Seems like you could just get a good quality pot of the proper value and sub it
Click to expand...
I don’t think so but not 100%.
Should just be a 500k log pot, I gotta get shaft dimensions.
 
The ARC supplied (in the 90s I think) replacement volume control was a stepped Alps Blue Velvet and a couple caps. Wasn’t expensive back then but that’s not what you need to do. Lots of pots out there for volume. I might recommend looking at tubelectron’s upgraded SP-3A-1 but that volume control is too much money to just fix this preamp right. Recent post of his.

The large volume knob on the stepped control has a very nice feel to it.
 
Blue Shadow said:
The ARC supplied (in the 90s I think) replacement volume control was a stepped Alps Blue Velvet and a couple caps. Wasn’t expensive back then but that’s not what you need to do. Lots of pots out there for volume. I might recommend looking at tubelectron’s upgraded SP-3A-1 but that volume control is too much money to just fix this preamp right. Recent post of his.

The large volume knob on the stepped control has a very nice feel to it.
Click to expand...
Honestly not finding much out there.

This might be an option:
 
Curious where those caps go.

1728567797064.png

The only thing that I can see that might be affected by the different volume control valueis the phono stage. Unless they are adding a small cap to ground to restore the original roll-off that the Miller of the first tube would have had in combination with the 500k volume pot.
 
gadget73 said:
Curious where those caps go.

View attachment 3316338

The only thing that I can see that might be affected by the different volume control valueis the phono stage. Unless they are adding a small cap to ground to restore the original roll-off that the Miller of the first tube would have had in combination with the 500k volume pot.
Click to expand...
He’s sending a photo of where they go, I’ll update the thread.

I’ll probably just buy it, they’re only 15 minutes away and then I can say it’s the true ARC replacement.
 
Looks good! I'd say getting it repaired for less than $150 is a good deal--even if you had to do the work yourself. ;-) I have to admire the fact that they walked you through it.
 
Interesting.
I have a SP-3 with a stepped volume control and it never occurred to me that the pot isn't original. (I bought my unit 12+ years ago and it didn't come with any service records.) Pot works beautifully so never gave it a thought.

Nice to see ARC with good support and agree that $125 including instructions is a deal.
 
zackthedog said:
Looks good! I'd say getting it repaired for less than $150 is a good deal--even if you had to do the work yourself. ;-) I have to admire the fact that they walked you through it.
Click to expand...

Jalousie said:
Interesting.
I have a SP-3 with a stepped volume control and it never occurred to me that the pot isn't original. (I bought my unit 12+ years ago and it didn't come with any service records.) Pot works beautifully so never gave it a thought.

Nice to see ARC with good support and agree that $125 including instructions is a deal.
Click to expand...

They charged me $80 for a part that’s literally still in the bag from Parts Express for $15.
That’s scummy business.

Not to mention the part doesn’t even fit!!!
The stub out on the control to hold it has no where to go, and the shaft is too long.

www.parts-express.com

CLEARANCE ALPS 100KAX2 100K Ohm Audio Taper Stereo Potentiometer 6mm Shaft

ALPS 100KAX2 100K Ohm Audio Taper Stereo Potentiometer 6mm ShaftThe Alps 100KAX2 is a 100K ohm stereo potentiometer of the highest quality. The 6 mm straight shaft is 25 mm long, with M8 thru-hole mounting, hardware included. The body of the potentiometer is 1.073" W x 0.97" H x 0.93" D (27 x...
www.parts-express.com

IMG_5049.jpeg
 
ivandezande said:
Not to mention the part doesn’t even fit!!!
The stub out on the control to hold it has no where to go, and the shaft is too long.
Click to expand...

ivandezande said:
Awesome!!!!!
Click to expand...
Guess the part fit with the nut on the shaft holding it to the inner panel and then the faceplate taking up enough space to allow the knob to go on and be properly positioned just off the faceplate. Other than cost, working out I hope.
 
Blue Shadow said:
Guess the part fit with the nut on the shaft holding it to the inner panel and then the faceplate taking up enough space to allow the knob to go on and be properly positioned just off the faceplate. Other than cost, working out I hope.
Click to expand...
There's zero space between the frame and the faceplate, as all the other controls have the same thread length. We'll see what ARC says.
 
Have to clip the nub off if there isn't a hole in the faceplate for it, or drill one. I'd just clip it off honestly.
 
gadget73 said:
Have to clip the nub off if there isn't a hole in the faceplate for it, or drill one. I'd just clip it off honestly.
Click to expand...
Yup, already did that. Turns out I needed to drill the frame out to fit, and the shaft is a little long but whatever.

They helped me through it, but for $80 it should fit right in, no drilling/sanding/praying.

image.jpg
 
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