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Pioneer SX-939 volume control

JohnMac

JohnMac

Addicted Member
Greetings,
I have a nice Pioneer SX-939 receiver with a broken volume control shaft. I'll have to replace the entire control. I don't want to give up on it but I'm having trouble locating the part. Apparently the design is different from most Pioneers in that it has four poles rather than three. Can anyone steer me on the right direction?

Thanks,
John
 
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The fourth terminal on the pot is for the loudness control...this allows the loudness to taper off as the volume is raised.
 
Does that mean if I substituted a three pole control the loudness function will be disconnected or it won't taper off?
 
Yep, that's what it means. Check eBay for a replacement. I recently saw a bunch of Pioneer parts listed there.
 
Ii is an ACV134, and it is used on the sx-737, sx-838, sx-939 and sx-1010.

http://parts.pioneerelectronics.com/part.asp?productNum=ACV-134

It's a dual 250k ohm, audio taper with loudness tap in which the tap is NOT PCB mounted. (iiac)

So, here's a question for you - HOW many steps are there on the pot?

markthefixer said:
"Are the volume pots in the sx939 and sx780/750 the same?"

First there's the question of what models have what pots.
answered by http://parts.pioneerelectronics.com

acv-134: sx-737, sx-838, sx-939, sx-1010
acv-179: sx-650, sx-750
acv-161: sx-450, SX-550, SX-580, SX-680, SX-780/790, SX-880/890

Then there is the deeper question of what could be substituted.

acv-134 : 250k audio taper, flying loudness tap, unknown # detents
acv-179: 100k, audio taper, loudness tapped for pcb, unknown # detents
acv-161: 100k, audio taper, loudness tapped for pcb , NO detents


acv-181 (sx-3800) 100k, audio taper, loudness tapped for pcb, 40 detents
AND IS STILL AVAILABLE FROM Pioneer for $20.50. Same resistance, taper, loudness tap and physical configuration as the acv-161... I KNOW. I did ALL the HOMEWORK!!!

The biggest question is the physical mounting configuration, pc board, but it looks like the loudness tap is a flying lead.
Click to expand...
 
Great info. I gave the unit to someone to work on because he thought he had the part so I don't know how many steps there are. Forgive my dumbness but what do you mean by steps? Now I need to somehow determine if the ACV-134 will mount in my chassis. Any more info will be appreciated.
 
JohnMac said:
Forgive my dumbness but what do you mean by steps? Any more info will be appreciated.
Click to expand...

Meaning a click for each volume setting. The volume controls are not stepped on these receivers. I know the SX1010 has stepped bass and treble controls.
 
EchoWars said:
The fourth terminal on the pot is for the loudness control...this allows the loudness to taper off as the volume is raised.
Click to expand...

Are you saying the loudness switch effects the sound differently at low listening levels as opposed to higher listening levels? (ie the loudness switch boosts high and low frequencies more at low levels than at high levels?)

If so, very cool. Didn't know this.
 
EchoWars said:
I had a 939 for a while...no detents.
Click to expand...

+1

My son has an SX-939 which I just now finish getting all the parts for the missing or broken parts from ebay. Volume control does not have any detents just like my SX-1010. I hate detents for volume control.
 
johnnm said:
Are you saying the loudness switch effects the sound differently at low listening levels as opposed to higher listening levels? (ie the loudness switch boosts high and low frequencies more at low levels than at high levels?)
Click to expand...
That is correct. It is very common in vintage gear.

Thing is, it tapers off too slowly in most gear. Better to save your speakers and amp by not attempting to rely on it...turn off the loudness before you decide to crank it up.
 
So EchoWars, does that mean that I could use a 3 pole control if I don't mind not having the loudness feature? The guy working on it thinks he has one that would fit. I seldom use loudness anyway.
 
JohnMac said:
So EchoWars, does that mean that I could use a 3 pole control if I don't mind not having the loudness feature? The guy working on it thinks he has one that would fit. I seldom use loudness anyway.
Click to expand...

Yeah, you could. But, I'll die without the loudness feature. I use it quite often. :D
 
Pioneer SX 1010 - Repacement pot volume control.

markthefixer - if you are still out there... can I ask where I can buy a replacement for the Pioneer SX 1010 Volume pot?

Went to the site you listed aboe and they do describe in detail but no longer sell it.

Can you tell me where to go for this part?

If my only option is ebay then can I look for parts from the receivers you listed above?

I'd rather just buy a new replacement if there is such a place that sells it. If you know of place can you also include the part number?

Sorry to be a pain but I have a mint 1010 that has a bent shaft. Works fine but bent shaft :thumbsdn:
 
:thmbsp:+2 y'day's Audio:thmbsp:. Just got a complete 939 faceplace and a HI/LOW/-20db switch assy from Danny. He's got the parts, easy to work with and faster than a scalded cat with shipping. Less than 48 hours from ordering to drop off. :banana::banana::banana:

Larry
 
logaEexpress said:
Pioneer SX 1010 - Repacement pot volume control.

markthefixer - if you are still out there... can I ask where I can buy a replacement for the Pioneer SX 1010 Volume pot?

Went to the site you listed aboe and they do describe in detail but no longer sell it.

Can you tell me where to go for this part?

If my only option is ebay then can I look for parts from the receivers you listed above?

I'd rather just buy a new replacement if there is such a place that sells it. If you know of place can you also include the part number?

Sorry to be a pain but I have a mint 1010 that has a bent shaft. Works fine but bent shaft :thumbsdn:
Click to expand...

You'll need to find the control from a parts set (the models which cross to this part which work have been mentioned already). Plan B: Mark Oppat of Old Radio Parts could rebuild your volume pot (not cheap).
 
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