• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer SX-780 no audio and no relay click

KosanRio

KosanRio

New Member
Alright first off before I even describe my problem I am extremely uneducated about these type of electronics, I'm more your "build your PC" kind of guy so I really know nothing about this sort of stuff (Soldering, Capacitors, voltage, fuses, stuff like that)

My problem: I plug the Pioneer SX-780 and turn it on and all the lights and such come on and the little FM thingy seems to go up when I select an actual station, but I get NO AUDIO (I can hear a very very faint sound with my headphones) I don't hear the relay "clicking in" like some forum posts I have read about this problem say. What should I do? I've already taken the top and bottom covers off to see if I could find anything wrong but I don't see anything out of place.

Pictures
Bottom: http://dl.dropbox.com/u/52134711/SAM_0973.JPG
Top:http://dl.dropbox.com/u/52134711/SAM_0972.JPG
 
Register to hide this ad
Welcome Aboard!

Do you have a multimeter? Solder iron? Good work area?

The topside photo is encouraging since it reveals none of the Sanyo light blue electrolytics of death.
 
Yes I just bought a soldering iron and I have a voltage meter, though I don't know how to use either of them.
 
I've got 3 4A 250V fuses, should I just replace all four just to see? I already replaced one that was blown.
 
in a word no . unless you are going to power it up with a dim bulb tester . you may cause more problems and waste fuses otherwise .
 
Which fuse was blown, what was its rating, and what rating fuse did you install in its place?

In looking at the bottomside photo, it appears that FU4 was replaced. It should be a 4A, and slow-blow is reasonably safe in this location.

That fuse feeds the main power transformer, and it it blows repeatedly there is some diagnosis to be done before powering up again and causing more damage.
 
Last edited:
Does the green source light in the center of the display light up when you power up? If not do a search on the SX-780 and you will find tons of info. That would probably be a power supply problem.
 
Watthour said:
Which fuse was blown, what was its rating, and what rating fuse did you install in its place?
Click to expand...

The blown fuse was rated at 2A 250V, but the board said it needed 4A 125V, I replaced it with a 4A 250V fuse, It's the fuse to the right.
 
Silverman said:
Does the green source light in the center of the display light up when you power up? If not do a search on the SX-780 and you will find tons of info. That would probably be a power supply problem.
Click to expand...

The green source light DOES light up.
 
The other fuses should NOT be 4A. FU1 should be 2A and it feeds the dial illumination. FU2 and FU3 should be 1A fast blow only. They feed the electronics. If either of those blow repeatedly you should assemble a dim bulb tester and then power up for diagnosis as Pete suggested.
 
Watthour said:
The other fuses should NOT be 4A. FU1 should be 2A and it feeds the dial illumination. FU2 and FU3 should be 1A fast blow only. They feed the electronics. If either of those blow repeatedly you should assemble a dim bulb tester and then power up for diagnosis as Pete suggested.
Click to expand...

The three ones besides the very right one I replaced all match what the board says it needs and aren't blown.
 
One thing you can do is power down the unit, safely prop it on its end, and closely inspect the solder joints and traces in the are within the yellow circle.
 

Attachments

  • SX-780_0973.jpg
    SX-780_0973.jpg
    119.5 KB · Views: 499
If you look closely it appears that the solder on those leads has a different appearance than the solder joints on the rest of the board. That device gets quite hot in normal use and can actually melt the solder, allowing to to flow away from the joint and cause a loss of connection. This usually renders the unit "dead" except for the lamps and perhaps the tuner and preamp.

As a preventive measure, it would be a good idea to prepare your new solder iron (tin the solder tip properly), clean the area, and re-solder the connections with good tin/led rosin core solder (or apply solder paste before soldering). Read the instructions or search on line for soldering suggestions and hints.

You might want to practice on some surplus copper wire or other items before re-flowing these joints.
 
Watthour said:
If you look closely it appears that the solder on those leads has a different appearance than the solder joints on the rest of the board. That device gets quite hot in normal use and can actually melt the solder, allowing to to flow away from the joint and cause a loss of connection. This usually renders the unit "dead" except for the lamps and perhaps the tuner and preamp.

As a preventive measure, it would be a good idea to prepare your new solder iron (tin the solder tip properly), clean the area, and re-solder the connections with good tin/led rosin core solder (or apply solder paste before soldering). Read the instructions or search on line for soldering suggestions and hints.

You might want to practice on some surplus copper wire or other items before re-flowing these joints.
Click to expand...

Could you show me the exact spots?
 
Check the three circled in yellow. The one circled in red is also a bit suspicious.
 

Attachments

  • SX-780_0975.jpg
    SX-780_0975.jpg
    100 KB · Views: 206
btw thanks for the help you guys! I've really got to sleep so I'll mess with this stuff tomorrow, thanks!
 
SX 780 had cold solder problems with two power ???? that had two small a heatsink if I remember right. That's where he needs to look.
 
You must log in or register to reply here.
Back
Top Bottom