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Pioneer SX-850

Stereo AM/FM Receiver (1976-78)

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Pioneer SX-850


The Pioneer SX-850 is a high power AM/FM stereo receiver with super-quiet phono equalizer and outstanding FM selectivity/sensitivity.

How do you know when to trust a stereo receiver to fill your musical needs?

Power output by itself is not much help, because unless your listening room is the size of a concert hall, a receiver with far less than concert-hall-sized output will do nicely.

The answer, obviously, is to put your trust in the circuitry the kind that you'll enjoy in the pioneer SX-850.

It delivers a continuous power output of 65 watts per channel, min RMS at 8 ohms, from 20 to 20,000 Hertz, with no more than 0.1% total harmonic distortion.

But even more importantly, it has the strength and finesse to handle that power with a healthy respect for musicality.

The SX-850 has a super-quiet phono equalizer in a 3-stage direct-coupled design to achieve wide dynamic range and +- 0.2dB RIAA equalization accuracy.

A FET in the Tone Control section, plus a 2-step frequency turnover switch for Bass and another for Treble, 2-deck monitor/dubbing, 2-system speaker drive, separable pre/main and more, mean further control versatility.

The superb FM/ AM section uses a dual-gate MOS FET and a 4-gang variable capacitor to boost sensitivity and selectivity, a PLL IC in the multiplex to improve stereo separation, and a special Integrated Circuit in the AM for still better reception and less noise.

It's the Pioneer SX-850 - the one you can trust to keep faith with your musical needs.


Tuning range: FM, MW

Power output: 65 watts per channel into 8Ω (stereo)

Frequency response: 10Hz to 50kHz

Total harmonic distortion: 0.1%

Damping factor: 25

Input sensitivity: 6.5mV (mic), 2.5mV (MM), 150mV (DIN), 150mV (line)

Signal to noise ratio: 70dB (MM), 90dB (line)

Output: 150mV (line), 30mV (DIN), 1V (Pre out)

Speaker load impedance: 4Ω (minimum)

Semiconductors: 3 x FET, 3 x IC, 56 x transistors, 36 x diodes

Dimensions: 526.6 x 173 x 411.5mm

Weight: 19.1kg

Accessories: FM T-type antenna

Year: 1976


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Reviewed Oct 04th, 2017 by seaswimmer

Great looking piece of gear but I've found that when I connect my record player to the Phono One, the music is barely audible. If I connect it two Phone Two, the volume is normal. Am I doing something incorrect?

Reviewed Jul 21st, 2015 by rtksjones

I bought my sx850 knowing it didn't work. This is where you get the best value. I replaced a transistor in the power supply and she sprang to life. I was so blown away by the sound of this receiver. I remember drooling over these systems back when I was at Georgia Tech; of course I couldn't afford one back then. I rediscovered these beautiful systems when a friend asked me to repair is sx1980; talk about a monster! You won't go wrong buying one of these babies. The sound is absolutely over the top; tight and clear lows and sparkling highs. Enjoy.

Reviewed Mar 20th, 2015 by rjermance

great vintage tuner/amp

Reviewed Jan 10th, 2015 by slimjim00

Excellent Receiver. Very Clean and Crisp sounding. Many filters without overdoing it.



re: SX-850

I have a sx 850 and a sg 9500. I cant seem to figure out how to hook up the equalizer. Any help would be great.

re: SX-850

Even better suggestion, is to connect this unit to the "Adaptor" section of your 850. All SX-850s have the Adaptor section and they are specifically made for connecting components such as EQs. That's how I have mine connected, which is the exact same as yours, SX-850 and an SG-9500.

re: SX-850

Hi, have you check the instruction manual for the SG 9500? it's available on this site.

From what I understand, you connect it between the tape deck and the receiver.
If what you want is to use the equalizer on every source of the receiver, then I'd suggest you connect it to the pre amp out and back in. Remove the bridges and connect the cables to and from the SG 9500. Word of warning though, I haven't tested this so it's just a suggestion that you should check, research and make sure it's safe before trying.

Good luck

re: SX-850

Thank you for your assistance. I was able to connect it to the tape deck input 1 and will now connect my reel to reel to tape deck 2. I now find that my receiver gives me a strong hum when I turn up the volume from playing my turntable. What could this be? The ground is connected to the eq. I tried the ground on the receiver and it still gave me a humming sound when volume was turned up. Hope this makes sense.

re: SX-850

I have had a Pioneer SX-850 that my brother bought brand new in 1977 and it has been stored for many years. Still works great but the volume knob when you turn it up is scratchy for lack of a better word. Does it just need to be cleaned?

re: SX-850

"Scratchy" noises can often be fixed with only a simple spray cleaning of the pots (potentiometers= which are the round main bodies for the adjustment of tone, volume, ETC...) and other switches. Usually this involves removing the outer case to access the internal parts. Some units need to have other parts removed in order to get to the pots. But you should not have to remove the pots themselves as long as you can get the spray into the pots through openings between the parts that cover the units. I personally have never used "Deoxit" which is a proper brandname for a certain companys cleaner, but it is highly touted online as a great product. I use a good brand of "Electronic contact cleaner" or tuner cleaner spray because that is what I already have around. Spray the pots liberally inside & out and turn the knobs in both directions to make sure all areas get wet. Following the cans directions is always a good idea to get the best results from the product used. Good luck and keep track of any screws removed so the unit can get put back together correctly. I love all those great vintage audio products made by Pioneer, Sansui, Kenwood, and the rest of the Japanese companies back when high quality was built into their products by workers that had pride. Not like the Chinese crap that we buy and toss in the trash these days.

re: SX-850

I have a SX-850 that I found at a dump some years ago (!) . I was using it for a long time and really liked it until it stopped working for some reason and I just put it in my storage - thanks to hifiengine, I have now the rep manual and I'll have a look if I can fix it - will come back here soon, either with a success history or asking some questions :-) (My guess without opening it would be problems with the capasitors in the power supply)

re: SX-850

Hard to say what the exact component is. Should check fuses, followed by power supply voltages in order to get a start on diagnostics. Go to audiokarma pioneer site for more input.

re: SX-850

I have 2 turntables hooked up to my 850 and I notice that sometimes the right channel goes a little soft, and if I play with the phono select button it comes back in strong. is this just a dirt problem has anyone had this problem? it happens on both phono buttons but not on FM or AUX

re: SX-850

I've owned this unit since I purchased it brand new in June of 1976, it has worked fine until about a month ago when it just stop working. When I used to turn it on, it would be a second or two before it
came on which was normal I would get a clicking sound just before came on, now it does not make the clicking sound all the lights come on but nothing else works what could be the problem ? Can anyone tell me what to look for before I take it to a service repair shop.

re: SX-850

Most likely a failure of transistor Q5 on the power supply board, common to this model at this age. For the info you need to remedy this problem, see this thread at AudioKarma: http://www.audiokarma.org/forums/showthread.php?t=354538

If you are at all handy with a soldering iron, this is a fairly easy task. There are several acceptable substitute transistors. I used a 2N4401, which I had on hand, as noted in this thread: http://www.audiokarma.org/forums/showthread.php?t=119787

Good luck!

re: SX-850

I've purchased the new transistor and I have all the manuals and diagrams for my SX-850, I'm having a problem locating the exact location for the Q5 transistor, I think I might be looking at Q7 but I'm not 100 % sure, does anyone have photo of the location of the Q5 transistor ?


re: SX-850

I was able to find the Q5 location on the printed circuit board, I desoldered the old transistor out and installed the new transistor and now everything works fine and it sounds great. Thanks for the help and also for the tips thanks again

re: SX-850

My 850 has had all the static producing knobs and switches detoxed yet when I use either of the Phono Inputs (for a brand new turntable) the right channel lacks power: it's quiet, and I can hear much more of the vinyl record blemishes (crackling, ticks, pops) coming from that channel specifically as compared to the left. However, when I use the toggle switch from Stereo to Mono, the balance comes back. To narrow down the problem I've switched speakers so I know it's not them. I also run my DVD player through the AUX input and the sound seems to be almost perfectly balanced. I know nothing about all the internal electronics of these things but I've read through a few forums that suggest that maybe the transistors for the Phono Inputs are dead, damaged, dirty, etc. Any help on this matter would be highly appreciated.

re: SX-850

my left channel seems to quit at random and come back on at random. Could this be corrected by removing case and blowing air into it to clean dust out? Doesn't happen all the time but seems to be increasing.

re: SX-850

Have you tried deoxiting the pots and switches yet?

19vintage61's picture

re: SX-850

First time visitor to HiFi Engine. I'm typing this at 4:00 am so bear with me. I just found out I was the winning bidder on a Pioneer SX-850 Receiver!! What a beautiful piece of vintage gear. So my first thought was getting an owners manual for it. A Google search brought me here. After a simple registration process I downloaded my manual. Thank you HiFi Engine :)

WOW, great site~! - Just

WOW, great site~! - Just picked up one of these that works great.

just purchased sx-850

just purchased sx-850 and in pretty good and working condition
any advises what speakers should I purchase ? if possible not large.


re: just purchased sx-850

I use Cerwin Vegas E-712 Speakers, and they sound awesome!

re: just purchased sx-850

I am using a set of bookshelf pioneer cs330's and they sound excelle this system. I have yet had to turn volume up past ten o'clock position and usally stay around nine o'clock. produces clean and crisp sound

Sx850 right side

Have had this receiver since the seventies. The right side does not play at all. Great unit. Would love to get this cranking again. Any advice would be great. Thanx

Have you tried deoxiting

Have you tried deoxiting the pots and switches yet?

Sx850 right side

yen, thanks for replying. I have taken off the top cover to take a peak and found it to be quite dusty. Could you give some guidance to pots and switches.


I have had this Pioneer SX-850 since the 70's - it is a great stereo - a really fine sound. However, I haven't been using the phonograph until recently and there is a loud hum when I push in either of the phono switches. I have disconnected the cable and TV and it is plugged into the same outlet as the phonograph. The hum happens even if nothing is plugged into the phono jack in the back.

Any idea what this might be?

thanks for any help

SX850 hum

The phonograph inputs go through a Equalizer Amp circuit board. The signal from the turntable is not as strong as the other inputs so it runs through an amplifier. No other inputs use this amp. It is possible that an electrolytic capacitor is bad. A loud hum normally indicates a ground problem. Some of the capacitors on that amp board connect to ground. If the SX850 works with all the other inputs, I would check this amp (pre amp) board.


picked up a sx850 at a yard sale for $25.00. it was looking dirty. washed it, polished the knobs and some liquid gold on the wood. wow! looks brand new. not one single ding or scratch. works perfect. running throuch a kenwood 20 band eq pushing 2 sets of cerwin-vega's, one set are d-9 and the other are ls-15. the sound is incredible!

Just purchased a Pioneer SX-850 on ebay for $93

Thanks for having the manuals online. The plexiglass faceplate is broken; but, the unit is supposed to be working fine otherwise and still looks good in the photos. If all is true it should be a fine addition to my home. I have an Onkyo tx 8811, Pioneer cs 822A speakers, I have a pair of cheaper pioneer 12" 3ways in the garage I picked up at a garage sale for $20. Now I just have to decide which reciever goes in the garage.

SX-850 protection mode issue

I have an Sx-850 and an SX-980. Both units have the same problem. They will go into protection mode when the volume is turned up anywhere near its midpoint.

Have used different speakers thinking the speaker load was causing the problem. My Sansui 7700 works perfectly with the same speakers I used with the Pioneer units. What can I do to fix the problem?

The Pioneers sound great when they work!

Thanks in advance for any help.

re: SX-850 protection mode issue

what size wire are you using? to small a wire will cause a high Independence and kick out the safety circuit . i use #12 awg. (stranded)

re: SX-850 protection mode issue

"Impedance". Not "Independence". : - )

re: SX-850 protection mode issue

Recalling from early 80's ... I believe I had similar issue and took it to audio repair. I recall they replaced heat sinks and all was well. Back then I think I was charged $50 for parts and repair. That has been the only issue with this receiver. Still works today after having it stored (in garage .. bad idea) for 15-20 years.

ha .. just realized how old this post was. still could be helpful, i guess, as there is a big demand for these legacy receivers.

SX-850 protection mode issue

I am no tech, one thing you may try is take off the cab to give it some air and see if it is a heating issue.
If your unit is in a confined space, temp rise. And while your in there you can clean things out to make sure its
not some contact issue. Try putting on the low pass filter, and reducing bass as you increase volume. Make sure that speaker wires are not contacting each other due to vibration. Try different speakers, not a different amp.
Good Luck.

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