I just bought a Pioneer SX-838 receiver. It lights up but I cannot get any sound to come out. The RCA jacks all have some oxidation as well as thepeaker outputs The fuse on the back panel is good and the "Tuning" dial indicates that it is receiveing something with an antenna hooked up. The "Signal" indicator doesn't move at all no matter which input I use.

I popped off the cover and everything looks straight as a pin. There is no smoke smell or any soot on the inside of the cover. I see nothing that looks like anything would be wrong.

Outside the unit looks very good with only minor scuffs. The feet are all present. The lights all work. The knobs and slides are all there and tight. All in all it's a very nice looking unit. Only the oxidized inputs and outputs and some dust on the interior are clues as to what might be wrong.

I have a multimeter and some novice electronics skills and I have built 6 pair of speakers so if anyone could possibly give me a hint at the problem I may be able to fix this unit myself. It would be a fun project either way.

Welcome to AK, MikeyTN.

I've a SX-838 as well, very nice receiver. There is one simple, but very very common issue with these older Pioneers when you just pick one up that causes the whole thing not to work -- missing jumpers. Basically, on the back of that 838 there should be a group of 4 RCA jacks that are labeled "Pre-Out" and "Power-In". There should be two u-shaped metal rods that connect these together and thus connect the pre-amp section of the receiver to the amplifier section.

- JP

You know It's funny you mention that, I have no electronic skills but twice now I have seen recievers on Ebay that claim the unit powers up but makes no sound. And both times when they show the back, the jumpers are missing?? Is this some kind of Ebay trick or do You guy's find this alot?// Is it worth 200 bucks to take a chance?

I wanna know where all these jumpers go... I mean what else are they good for?

Miniature games of horseshoes?
U nails for fence repair?
Nostril rings for the younger set?
Staples for a really thick stack of papers?
Bent double to make cheap wedding rings?
A really small croquet set?

I'm just riffin' here, but seriously, what in the world is happening to all these missing sets of jumpers? I'm beginning to think people assume they're some sort of home-made junk, yank them, then wonder why the unit won't work.

Or they get a unit that's junk and take pictures of the back with no jumpers and suck some POOR soul in, But on the other hand it's 50/50 that some Idiot pulled them out, I guess it's possible if someone wanted to put an EQ inline and then the system was taken apart and ???? There is one on Ebay right now at 202.00 Mighty tempting, And oh yea it's a 1250

My jumpers are there. I just checked and took a picture. I have pictures of this unit if anyone would like to see them.

Thats a good question! I think the user had attaches equilizers or reverb units to their receivers, somebody pulled the stuff appart and is wondering why the unit is no longer sounding and does not understand why. Thats good for us!!! I think many jumpers lay around somewhere without use!

Good question. Over half of the vintage receivers I've seen at the thrifts were missing their jumpers. It's incredibly common and extremely confusing. I doubt that so many people with vintage receivers used them as pre-amps for separate amplifiers. So, my best guess is that some ill-informed back room workers at the thrifts are doing as Fotno suspects, pulling the jumpers as some hack. (All my thrift receivers have been missing their jumpers, but garage sale rigs have them.) As to pulling them for an equalizer, I doubt it as the level at these jacks varies with the volume knob when there's good. As equalizers are designed to work with tape in/outputs in the first place, and many of these old Pioneers have noise adapter hook-ups as well, it doesn't seem likely for that to be the case.

- JP

My jumpers are there. I just checked and took a picture. I have pictures of this unit if anyone would like to see them.
You can attach pictures to a post so long as they're resized to be under 900x900 pixels and 200 kb in size. Pictures are always a good thing.

Ok on the jumpers. There are other simple things that could be the cause and it's best to work from the simplest to the more complex. Have you checked the switches and buttons in their different positions? The levers for the tape monitors and Dolby NR adaptor need to be in the up position. After this, try pushing in the button for FM muting and listen for static. Have you connected a pair of speakers to the receiver? If so, have you depressed the appropriate speaker selector button (black at the bottom of the dial on the left)? Have you tried headphones?

Since you said you've already been inside, did you check all the internal fuses as well?
- JP

I have not found any internal fuses. Just the one on the back panel.

I have connected one speaker to the using the main set labeled "A". I checked all the other speaker outputs and didn't get anything from any of the either.

I have moved all the levers around to their different positions and pushed every button on the unit and have not even gotten so much as a thump.

I have not tried headphones and I will make sure my speaker actually works.

Ok. My speaker works and I am using my Sony receiver as a reference to make sure that everything I test on the Pioneer works on the Sony. I need to buy some headphones this evening so I can rule that out.

I have had the unit turned on all day and no funny smells have been noticed.

What is that "Signal" Indicator next to the "Tuning" indicator dial? Does that mean signal from an aux. source such as a CD player of turntable? 'Cause it hasn't moved once since I started checking this unit.

There are 5 fuses (4 @ 1 amp and 1 @ 3 amps) on the underside; you'll need to pull off the black cover that composes the bottom. The headphones allow for you to generally isolate the problem, whether it is in the pre-amp section or the amplifier. As you don't have a pair just yet, you can remove the jumpers and connect the pre-out to your Sony's Aux input to test if you're hearing anything through there.

The signal indicator meter indicates how strong of a signal the tuner is receiving from the AM or FM station you're tuned to. If you've an antenna connected to the FM antenna connection and tuned around the dial in FM mode, you'll have seen the meter go up as you tune to a known strong station. If not, then something else is afoot and beyond my ability to help at the moment. However, I doubt that it is sharing in the same fault as the rest of the unit.

Here's a question, when you turn it on, do you hear a click inside the receiver a few seconds afterwards? This is the protection relay that disconnects the final amplifier section to prevent damage if something is afoot. Quite often, a couple of caps or a transistor can go bad in the protection circuit and thus cause the relay to not engage. This means no audio and is just as effective as pulling the jumpers. Still, the pre-amp should still work in this case.


While you're out picking up headphones, you'll want to purchase a can of Caig's DeoxIT, which is available at most Radio Shacks. It's an excellent contact cleaner and you'll need it to clean the balance pot and switches after you get the 838 working.

- JP

All the fuses were good.

I didn't hear a click inside the receiver after turning it on so the relay is potentially my problem. I have auxillary lighting on my truck wired through a relay and if I am under the hood I can hear a click when it turns on. This is looking like it is my problem.

I have now gotten sound to come through the unit but not on it's own. I ran a CD player through the phono 1 input and ran RCA cables out the pre-out after removing the jumpers. Then the RCA patch cord went into teh auxillary input of my Sony receiver. It played music but there was some static. I guess from the oxidation.

So, it seems my problem is with the amplifier section of my unit. A faulty relay is #1 suspect and heavy oxidation on the inputs is also a liability to the function.

Now, how can I get a replacement relay?

Relays are likely the most reliable part in the receiver. The protection circuit that drives the relay is the trouble 99.99 times out of 100.

Relays are likely the most reliable part in the receiver. The protection circuit that drives the relay is the trouble 99.99 times out of 100.

Now how does this new information help me?

I need to know what to check. How to check it and how to find a replacement.

Any books out there on this subject?

Thanks for the help!

Now how does this new information help me? Helps you by preventing you from buying a relay that won't do a thing to fix your problemI need to know what to check. How to check it and how to find a replacement.

Any books out there on this subject?The service manual would be the place to start.

You can also look at this thread (http://audiokarma.org/forums/showthread.php?t=52157), and in post #10 I showed the protection for the SX-1010, which is essentially the same for the 838.

What you need to determine is if the protection is doing its job by keeping the relay from engaging because the output of the amplifier is fOObar, or if the output of the amp is OK, and the protection circuitry is at fault. A quick and dirty check for the amplifier is to measure the DC voltage on the emitters of the output transistors...pin #27 or pin #30 for the right channel, and pin #33 or pin #36 for the left channel. The DC voltage at any of these pins should be well under 100mV (0.100V). If the voltage at any of these pins is at more than a couple of volts, the protection will not allow the relay to close.

Edit: You can also, of course, measure the output DC by finding the 'Common' terminals on the relay itself and measure it there.

On the protection board itself, look at the DC voltage on pin #11. Should be 35V (or thereabouts). If it is very low or not even present, then you have voltage regulator problems instead of protection circuit or amplifier problems.

If the voltage on the emitters looks OK, and the 35V is OK on the protection board, then the driver transistor on the protection board is very likely bOrked (dontcha love tech terms?), or the differential pair on the protection is out of balance, or one of a number of other things which are possible but less likely.

Helps you by preventing you from buying a relay that won't do a thing to fix your problemThe service manual would be the place to start.

You can also look at this thread (http://audiokarma.org/forums/showthread.php?t=52157), and in post #10 I showed the protection for the SX-1010, which is essentially the same for the 838.

What you need to determine is if the protection is doing its job by keeping the relay from engaging because the output of the amplifier is fOObar, or if the output of the amp is OK, and the protection circuitry is at fault. A quick and dirty check for the amplifier is to measure the DC voltage on the emitters of the output transistors...pin #27 or pin #30 for the right channel, and pin #33 or pin #36 for the left channel. The DC voltage at any of these pins should be well under 100mV (0.100V). If the voltage at any of these pins is at more than a couple of volts, the protection will not allow the relay to close.

Edit: You can also, of course, measure the output DC by finding the 'Common' terminals on the relay itself and measure it there.

On the protection board itself, look at the DC voltage on pin #11. Should be 35V (or thereabouts). If it is very low or not even present, then you have voltage regulator problems instead of protection circuit or amplifier problems.

If the voltage on the emitters looks OK, and the 35V is OK on the protection board, then the driver transistor on the protection board is very likely bOrked (dontcha love tech terms?), or the differential pair on the protection is out of balance, or one of a number of other things which are possible but less likely.

Damn, that's alot of information. Wish my 838 was down and not the 939.

mac