SX-980 Output Problem

G

gjimmy

Member
Hello there,

Last month I bought a great SX-980 from an audio specialist in Los Angeles and have been loving every minute of it until a few days ago I realized that the right channel was considerably lower than the left. I have to move the balance knob to the 2 o'clock position in order for them to pump equal wattage.

This seems to take down the overall volume quite a bit on my unit and I am concerned about it.

Has anyone had similar problems with any of their receivers? What could cause this? What can be done to fix it?

Any help is appreciated!

Thanks so much


Pioneer SX-980
Marantz 6300 Turntable
 
VintageNut said:
always try the easy fix first. Clean the controls with De-Oxit
Click to expand...
Welcome to AK
You can also try hooking the speakers to B posts and see if you have the same problem. Working the speaker A button at low vol to see if it goes back to equal bal. Did it work fine when you first got it?

Ron
 
IMHO swap the l/r speakers and see if the balance problem moves... then blame the amp. I don't remember if there is a "mono" switch in it...
see if that makes a difference. all easily and quickly done....

a/b speaker connections won't eliminate a protection relay contact problem,
then break out the deoxit for short bursts directly into the controls...
but that requires opening it up...

Anybody: what is the protection relay in it?? socketed or wired?
also are there any fuses in the output circuit???
what about pre-out to main in connections???

edit: hmmm assumption is that output circuitry FROM amp is ok....
pre-out to main in swap channels or connect so that l/r amp has the same signal input...
 
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I have not hooked the speakers up to the B set yet, however it seems to be the main output as the wattage Meters are what gives this problem away. When the left channel is bouncing at 1 Watt, the right channel is at about .1. I didn't notice the problem when i first got the unit, so it could be a problem that is worsening.

I will clean the switches, but it seems as if it is an output problem moreso than a switch problem being that there is no scratchyness or noise coming from the balance knob and the meters are telling me that the right channel is weaker.

Any further advice?

Thanks for the help.
 
My first vintage item was a SX-1280. I knew nothing at that time, and still don't know much :D, It had a cutting out problem on one channel, you could see it on the power meter. A weak signal from the preamp side will reflect on the power meter. Turned out to be a dirty switch on the front panel (preamp side). You can remove the jumpers on the back, and test the amp by itself to see if is on the amp side. Just keep in mind you have no volume control that way. Good chance it is a dirty pot or switch
 
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VintageNut said:
My first vintage item was a SX-1280. I knew nothing at that time, and still don't know much :D, It had a cutting out problem on one channel, you could see it on the power meter. A weak signal from the preamp side will reflect on the power meter. Turned out to be a dirty switch on the front panel (preamp side). You can remove the jumpers on the back, and test the amp by itself to see if is on the amp side. Just keep in mind you have no volume control that way. Good chance it is a dirty pot or switch
Click to expand...

spot on.... I looked at an ebay pix of a 980, the center back rear has the four rca plugs with 2 "bars" between them. connect the two bars together to be SURE that the EXACT SAME signal is being fed to both amplifier channels.... you cannot be sure that a "mono" switch will do exactly that .... I had something similar with a sx-636 happen to me and that mono switch wasnt the last thing in the signal chain before the amplifiers...
 
just about any switch on the front panel can cause a problem of cutting out. Play it, and when the problem is evident tap and play with the front buttons and levers. You might find the problem
 
What is the best way to connect the two bars to ensure solid contact? Also what is the best way to hook up the pre-amp to test that? Where should that be connected? Thanks for the help, and I appologize if I am asking dumb questions.

Thanks!
 
quick dirty and CHEAP, this is just an improvised test.....
hard to say, anything handy.. I would use alligator clip lead, but I have a few around.
bare wire (Y shaped) about the size of (and penetrating only the depth of) an rca plug's center conductor or a finer bare wire just wrapped around the two "bars" NOT touching anything else....

no wire??? an aluminum foil strip carefully trimmed etc.....

If you have a Y type rca adapter and some spare rca cables, that would be optimal... (but expensive)

The obvious goal is one signal into both inputs....
and if the amplifier outputs are the same then blame the pre-amp section and the amp is blameless......

With 2 "rca" cables you can try swapping left and right at those plugs too.
If it is the pre-amp, a cleaning session is due.
The guys you got it from.... do they have a warranty???

I haven't opened a 980 for pot and switch cleaning, so then I will pass the baton.......
 
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gjimmy said:
What is the best way to connect the two bars to ensure solid contact? Also what is the best way to hook up the pre-amp to test that? Where should that be connected? Thanks for the help, and I appologize if I am asking dumb questions.

Thanks!
Click to expand...
If you have a 2nd receiver with pre outs main ins you can hook the pre out from the 980 to the amp in of the 2nd receiver to see if it is the pre amp of the 980. You can also connect the pre out of the 2nd receiver to the amp in of the 980 to see if it is the amp of the 980 with the problem. all this using RCA cables.
 
that's what I did. Connected another receiver's preamp to the amp. The Y connector is a good idea too. Get a Y connector at radio shack pretty cheaply. You could also connect up a CD player into the amp side IF the CD player has a volume control on it. Remember, you lose all volume control going directly into the amp in jacks on the back. It will play at full blast, unless you connect something that has a volume control on it..
 
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Thank you guys so much for all the help. I will try a couple things to determine the exact problem...but it sounds like a good way to start is with the DeOxit.

How expensive is that stuff? If it does the trick, which you guys say it does, I will buy it.

Thanks so much!!! I appreciate all the help!
 
If you are in a hurry, radio shack has a twin pack combo of 2? oz (breath spray size) deoxit and progold for $14.99 id#: 64-4338.. the small size helps to remind that a little goes a loooong way....

My suggestions were intended as zero cost quick tests to be done in between posts..

The y adapter is $3.99 and is id#: 274-303 and is 3 rca plugs, 2 female and one male...

If you are going to internet order the deoxit, I suggest getting some rca cables if you need them while you are at it... radio shack prices are :yikes:
 
STOP!

DO NOT TIE THE 2 JUMPERS TOGETHER. Y-jumpering is OK for connecting 1 output to 2 inputs, but NOT for connecting 2 outputs to 1 input. Here is why: If one output drives to -peak output and other output drives to +peak output, current from 1 output goes into the other output, with only the output impedence to limit the current. You could blow the outputs you tie together. Mixing must always be done through an impedence. You could get away with it, but that does not mean you have done wisely. Sorry gents. No offense intended.

Connect the preamp to the power amp using normal system interconnect wires. If the problem remains (it probably will), swap the left and right power amp inputs. If the symptom moves, the problem is with the preamp, if not, the problem is with the power amp.

Rich P
 
gjimmy said:
I have not hooked the speakers up to the B set yet, however it seems to be the main output as the wattage Meters are what gives this problem away. When the left channel is bouncing at 1 Watt, the right channel is at about .1. I didn't notice the problem when i first got the unit, so it could be a problem that is worsening.

<snip>
Any further advice?
Click to expand...
Wattmeters are far from a precision instrument (and can easily be out of adjustment). Trust your ears. And clean the pots.
 
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