Pioneer SX-990?

ok, a picture will not do this justice, but a verbal description from a halfway decent tech should do it
while looking in the bottom of the chassis, on it's transformer end upright. That puts the faceplate pointing left and the on-off switch down low to the table.

we have:
chassis ground b, a punched tab right above (to the left actually) the b+ terminal of the amp board
chassis ground a, a punched tab between the main cap and the amp board - and the cap is not grounded to it there.
chassis ground c, a soldered point right below (to the right actually) the b+ terminal of the amp board

signal ground for the pre-out / amp in plugs

next - the board pins by their own labels, left to right, component side, pin row facing viewer:
----------------------------
edge of board
out 1
--- short gap, then group of three
e3
e1
in 1
--- long gap until center
+b
--- long gap from center to group of three
in 2
e2
e4
--- short gap,
out 2
edge of board

and here is how they are connected:
out 1 long orange wire to speaker selector switch
e3 black wire to chassis ground a
e1 black wire to chassis ground a
e1 also has ground wire of yellow jacketed shielded cable to signal ground
in 1 white wire center conductor of yellow jacketed shielded cable to amp in left
+b brown wire to main capacitor plus terminal
+b also has 0.01uf cap to chassis ground c
in 2 green hook up wire 2" to amp in right
e2 black wire to chassis ground b
e2 also black hookup wire to signal ground
e4 black wire to chassis ground a
out 2 long white wire to speaker selector switch

hope that's clear enough
 
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I have a SX-990 in for repair, and all the wires were busted off the output board. Some tracks/terminal pins are broke and missing. Every time I think I have it figured out, I only got one side, then in re-wiring, lose it with a 'thumping pulse' sound with neither side working. I was looking for a nude shot of the wires connected to the output card, but the closest I came was a reworked one without the wires connected. CAN ANY PROVIDE ME WITH THE WIRING assignment to the output board? I think it's the ground wires I'm messing up. I believe all the grounds go to the E markings, but I'm not sure which ones....

btw, that was a thread hijack, you are welcome to, nay ENCOURAGED TO start your own threads to minimize confusion.
 
I've had one of these for 20-some years

I got one of these SX-990's some 20 years ago at the thrift store. I was impressed by the two meters. Unfortunately, one channel was out and the fuses were blown. Took me those 20 years to find a schematic and a replacement transistor. Couldn't have done it without the Internet and Fry's. Finally got both channels. Now all I have to do is find those speaker plugs.
The set has seen service as an aid to aiming my rooftop antenna, and feeding the preamp output to another amplifier has been helpful, but too many amplifiers in a pile was getting out of hand. Great sensitivity - could tune in Vancouver BC FM stations from Renton, WA, and also southwest Washington FM stations. Nice smooth tuning.
 
Hello everyone!

This is my first post here. I purchased a Pioneer SX 990 a few weeks ago from a local thrift store for $20. I plugged it in and the the left speaker channel is out and it needs a few of the tuner panel fuse lamps replaced. I do not see any screws to remove the front to replace the lamps. Does anyone know how to replace the fuse lamps and be able to tell me why the left speaker channel might be out and how to fix it? I would love to hear what this receiver sounds like from both sides and see the front fully illuminated. Thanks very much for any guidance!
 
The owner's/service manual and schematic can be downloaded here , you'll need to register though:

http://www.hifiengine.com/manual_library/pioneer/sx-990.shtml

If memory serves me, the top panel and front faceplate will need to be removed to get access to the tuner display and bulbs.

Give your receiver a good cleaning with Deoxit:

http://www.audiokarma.org/forums/in...diots-guide-to-using-deoxit-revisited.207005/

The left channel may be out due to a problem in either the preamp or output section, or as simple as a dirty switch.

I love the sound of my SX-990 and would have to find a great deal on a better receiver to consider using anythng else.
 
The owner's/service manual and schematic can be downloaded here , you'll need to register though:

http://www.hifiengine.com/manual_library/pioneer/sx-990.shtml

If memory serves me, the top panel and front faceplate will need to be removed to get access to the tuner display and bulbs.

Give your receiver a good cleaning with Deoxit:

http://www.audiokarma.org/forums/in...diots-guide-to-using-deoxit-revisited.207005/

The left channel may be out due to a problem in either the preamp or output section, or as simple as a dirty switch.

I love the sound of my SX-990 and would have to find a great deal on a better receiver to consider using anythng else.

Thank you very much for the reply! I really appreciate it. I will check out the owner's manuel, do a good cleaning and go from there. Hopefully the speaker issue is due to a dirty switch.
 
Would anyone have any guidance on how to remove the face plate on a Pioneer SX 990. I removed the lid and only see screws on the sides but they are partially obstructed. I do not see any top screws. Do I need an L shaped screwdriver to remove these obstructed screws? Thank you!
 
Pull all the control knobs off and you'll find washer nuts on some of the pots. These are holding the faceplate in place.

As for bulbs, I can't say aside from the dial pointer which is a "grain of wheat" bulb, which I happily found at a local hobby store's model train parts section.
 
Thank you very much! I was able pull off all the knobs except the tuner knob. Very stuck. Got the washers off as well. Thinking about how to best pull the tuner knob off without doing any damage. I tried putting a spoon wrapped in cloth under the knob edge to pry it loose but it will not budge. Any suggestions? And thank you for your advice on the sticky switch possibility in a previous post. I was able to play with the speaker speaker switch a little and now both speakers lines are working. Still waiting to get Dioxit so hopefully that will make the connections even better!
 
I have a Pioneer SX990 but a different problem. I connected a Technics turntable to it and when I played an album, there was a very noticeable hum. After reading other posts, I thought the inexpensive RCA cable I was using might be the problem so I ordered the Blue Jean LC-1 cable. When I received the cable, I tried to connect it to the RCA phono connections on the SX990 but it does not fit. The connector on the LC-1 is too small even though it looks to be the same size as the cheaper RCA cable I was using. I contacted Blue Jean Cable and was told they are standard connections and should fit any RCA connection. He even said they have never had a situation where it didn't fit and he suggested I push harder. I tried but was afraid of causing damage. Any suggestions?
 
I've had the same thing occur with mine. Seems like newer cables are a snugger fit than older ones, like on my PL-112D.
 
Does anyone know how to replace the amplifier fuses on a Pioneer SX 990. I was replacing the tuner panel lights with LEDs and the power went dead. Someone recommended replacing the amplifier fuses but I do not know where they are located. Thank you!
 
A lot of RCA cables have a sleeve over the actual plug, you can sometimes find a threaded portion of the sleeve, loosen it and it will allow you to slide the plug over the terminal , then you can retighten it and it will not fall off.
 
Does anyone know how to replace the amplifier fuses on a Pioneer SX 990. I was replacing the tuner panel lights with LEDs and the power went dead. Someone recommended replacing the amplifier fuses but I do not know where they are located. Thank you!
I don't know where the amp fuses are but I would like to know what LED bulbs did o
You use?
 
Does anyone know how to replace the amplifier fuses on a Pioneer SX 990. I was replacing the tuner panel lights with LEDs and the power went dead. Someone recommended replacing the amplifier fuses but I do not know where they are located. Thank you!

There are two fuses on the amp board, #W15-060. Under the metal mesh cage. I can't recall if the fuses are easier reached from the top or bottom.
 
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