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My New Pioneer SX-980, but afraid to use it... (DC offset high?!?)

EchoWars said:
Directly measuring current would require refitting the meter to measure current, and then placing it in series with the current path in some fashion. Difficult (as it would mean desoldering something to insert the meter in-line to the flow of current), and dangerous, as the meter configured to measure current is a direct short to whatever two points it is connected to and mistakes get costly. It is much safer to locate a resistor that the 'desired current to be measured' flows through, where you can measure the voltage generated by the current flowing through the resistor, and calculate the current.

This is why the bias (or idle current) is nearly always referred to as a voltage generated across a resistor (or pair of resistors) rather than some direct current measurement.
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Thanks for the info. Its just because with my Hafler DH-200, you pull out the B+ fuse, and measure the current and set it at 250mA-275mA. And with my Boston Acoustics plate amp, you remove a jumper, and connects the leads to the two terminals that the jumper bridges, and measure it and set it to 2.5mA.

But I understand it all now. Thanks for clearing it up Glenn!
 
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Seems adjusting-correcting for a non equal power supply pos vs neg, since both channels where affected the same.
 
JoeDotCom said:
I am loving this thing! I play it nearly every night. I have not owned a receiver that sounds this powerful. I love it!

Only thing it is missing is one of the switch cap/tops. (you can probably see it in the photos, it is missing form the mute switch)

Is there a good place that will sell me a single switch cover?
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Joe,

Send me your mailing address in a private message and I'll hook you up with a switch cover :thmbsp:
 
ryuuoh said:
In your first pic, that cap on the right has a shrunken jacket. Probably has had a hard life. Consider recapping the power supply for reliability.
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Saw that to...What I do when buying 70's equipment..recap recap recap. I would first thing to recap the Power Supply board 1st pic.
 
CohibaJoe said:
Saw that to...What I do when buying 70's equipment..recap recap recap. I would first thing to recap the Power Supply board 1st pic.
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I'm in! But I think it will need to wait until next month. I will work on ordering caps and looking up instructions in the next week or so, so I am ready once a spot on my "workbench" opens up.
welding.gif
(I could not find a soldering smiley... so we will have to make due w/ a welding one.)
 
tomrich22 said:
Joe, you think you love it now, wait till you have it recapped! I had mine SX980 recapped last year......and WOW!!!!!! You will hear the difference.
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That is really exciting to hear. I have only owned BPC and Home theater receivers so far, the sx-980 blows them all away already! Do you mind my asking... how much did it run you to have someone else recap yours? I am planning on learning/doing my own recap eventually, but i would love to have an idea of the cost should i get lazy and want to hand the work off.
 
Should I do the main power caps too? Are those the large pair that are by the big transformer ? Are those expensive parts? Compared to the little ones on the circutboard, I am guessing yes. They look easy enough to get to.

Sent using a mobile device.
 
Wow, Thanks reading this I able to just do mine perfect . It was so much off now both channel reading Right .00 , LEft .01.

Did you able to adjust Meter Amplifier? I need to do this but I don't know how to Apply 1kHz mean to Aux. Please anyone know please advice.

Instructions say: Apply a 1kHz sine wave to the input terminals (AUX) and adjust the input for an AC volt-meter reading of 28V.

I think it need equipment to do this?
 
Oldie but absolute goodie here! Exactly what I needed to set my new to me SX980 back to specs. The photos were awesome.

For those trying this for the first time like me - there are two boards, one for each channel, on either side of the heat sinks. Took me a little bit to figure that one out LOL!

I set the DC offset to around 5 on both channels by ever so slightly turning the blue pots with a small screwdriver. I used the speaker outputs on the back for the multimeter, just put the leads in the spring clips for hands free and easy reading. Then adjusted the white pots on both boards to right at 30 for the idle current. And yes, this adjustment is far less sensitive than the blue ones.

At first I was using a small screwdriver and turning the unit off each time I'd adjust. Those blue pots are just way to sensitive and a slight turn either clockwise or counterclockwise sends the reading up the wrong way again. I then turned the unit on and carefully engaged the screwdriver tip with the slot in the pot and dialed them all in.

Thanks again AK, great thread! And especially JoeDotCom for starting it. Now on to my Sansui 9090!
 
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