My garage SX-939 has low output on the phono; I have to got to 12:00 on Phono to get the volume 9:00 gives me on FM, Aux, and Tape.

It's not the cart either as I've swapped them about and both worked fine with comparable volume on another receiver. I found some pretty comprehensive posts on this issue on an SX-x50 models, but I'm not sure if the solution is the same. It's probably similar, so I'll douse the receiver with Deoxit on both Phono switches (pushbuttons) and the Mic inputs again and look for weak solder joints on boards. If this has been discussed before, please post a link; search seems to be having some issues as if I use more than 3 words all I get is a blank screen back and not even an "no matches found".

Thanks!
Andy

My garage SX-939 has low output on the phono; I have to got to 12:00 on Phono to get the volume 9:00 gives me on FM, Aux, and Tape.

It's not the cart either as I've swapped them about and both worked fine with comparable volume on another receiver. I found some pretty comprehensive posts on this issue on an SX-x50 models, but I'm not sure if the solution is the same. It's probably similar, so I'll douse the receiver with Deoxit on both Phono switches (pushbuttons) and the Mic inputs again and look for weak solder joints on boards. If this has been discussed before, please post a link; search seems to be having some issues as if I use more than 3 words all I get is a blank screen back and not even an "no matches found".

Thanks!
Andy

WOW, that's a pretty significant difference!!

Well, as you know you have separate positions on the function switch for MIC and PHONO, and it switches in(RIAA-phono) and out(mic) different equalization components in the equalization amp's feedback loop which COULD affect the gain if the switches were really messy (but I'd expect the gain to go UP, because there would be LESS feedback), BUT I would expect the balance between the channels to be affected as well.

The same goes for failing electrolytic caps, both channels would not go at once.

Thus we are left with the common element, which is the power supply. If something is wrong here, it would affect both channels equally.

So if you can rustle up a DMM, you would want to check for +25v at pin 1 and -25v at pin 6 (referenced to a metal chassis ground) on the equalizer amp assembly labelled AWF-013 on the underside of the chassis on the opposite side from the power transformer.

You also may want to get a service manual (electronic-from the database or paper from a vendor (rick at stereomanuals.com) if we need to correct those voltages.

Might mention that this generation of Pioneer receivers has rather low gain on the phono amp. I have a SX-1010 and a SX-939 here, and with my V15VxMR cart, the difference between most sources and the phono is huge.

I'm not saying you don't have a problem, but warning that this could be part of the way these receivers work. An FYI, so to speak.

Thanks guys, I have a DMM and I'll check it out tomorrow. I've had the receiver a couple of years and just never hooked up a turntable to it. I just added the turntable to preview LPs out in the garage w/o putting my "good" styli at risk. I actually pulled the 939 out tonight and soaked the 3 switches with DeOxit in hopes of getting the volume up, but no change.

I'll check out those voltages, but it's interesting that EW has a similar situation with his receivers. I've used a Stanton 681EEE and a Shure M97XE in the table and both show similar low outputs. Even swapped in a new set of interconnects with no change. I did swap in an SX-828 while I was messing with the 939 and it had a diminished phono output, but nowhere near what the 939 exhibits. Like EW hints, it just may be the way this beastie is.

I'll post again after I take a few measurements. BTW, i snagged the SM last night form the manuals archive. That's quite a resource there!

The interesting thing is that the Pioneer service manuals for the sx-1250, the sx-1280 and the sx-939 all claim the same thing, that the phono input is rated for 2.5 millivolts input for a 150 millivolt output using a gain of +35.5 dB....

Yet if EchoWars finds some models to be noticably low, well, I HAVE to believe him, and wonder what marketing hooie the writers were sniffing.

Check the supply voltage to the phono preamp. If it's low, it might corrupt the gain.

Fred

Check the supply voltage to the phono preamp. If it's low, it might corrupt the gain.

Fred
Ummmm....... :deal: :D:D


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Thus we are left with the common element, which is the power supply. If something is wrong here, it would affect both channels equally.

So if you can rustle up a DMM, you would want to check for +25v at pin 1 and -25v at pin 6 (referenced to a metal chassis ground) on the equalizer amp assembly labelled AWF-013 on the underside of the chassis on the opposite side from the power transformer.
<snip>