EdBacon
Active Member
Hey all,
I am working through some bugs with a Sony STR VX550 receiver. I initially received this with no sound output at all. I identified high voltages on the voltage and power amplifier STKs which were preventing the unit from leaving protection. After replacing these two ICs the unit now produces sound, but I have a separate issue with the button pad. One row of the grid is now unresponsive. I did not check all the buttons beforehand, but one button not working is now the volume down button, which was definitely responding before replacing the STKs.
I'm attaching the schematics here. In anyone's experience is there a way for STKs on the output end to interfere with function back around the CPU and button inputs? I didn't think this was likely, but it is too much of a coincidence for me this just happened after replacing those two ICs.
Link to schematic: https://www.hifiengine.com/manual_library/sony/str-vx550.shtml
Little more troubleshooting info:
Both the key lines into IC301 are held at 1V. When I press the up volume I get a little wobble in the voltage of about 0.2V. Nothing happens on the volume down key line. Looking on the oscilloscope I have the same 100Hz 3.8V signal on both lines. On pressing volume up I see two peaks appear on the working line. Nothing on the bad line.
Measuring over the volume down button pad looks like I see a 300mV signal when closing the switch. So looks like the button switch works but no signal getting to the chip. Bad cable? Bad connector?
Further updates: Found the issue. Broken solder joint where the key line for those buttons leaves the switch board onto a cable to the board with the processor. Looks like it just needs to be re-soldered.
Even more updates: Took off the button switch board. Looks like all the wires off that cable were holding on by a thread anyway so I'll just re solder all the connections. Not sure what happened. Seems like the front of this unit got wet and maybe there's been some corrosion.
One last update: reattached all the cables and tested. Buttons are all working again!
This one is going into my 1980s Sony stack. Love the look of these.
I am working through some bugs with a Sony STR VX550 receiver. I initially received this with no sound output at all. I identified high voltages on the voltage and power amplifier STKs which were preventing the unit from leaving protection. After replacing these two ICs the unit now produces sound, but I have a separate issue with the button pad. One row of the grid is now unresponsive. I did not check all the buttons beforehand, but one button not working is now the volume down button, which was definitely responding before replacing the STKs.
I'm attaching the schematics here. In anyone's experience is there a way for STKs on the output end to interfere with function back around the CPU and button inputs? I didn't think this was likely, but it is too much of a coincidence for me this just happened after replacing those two ICs.
Link to schematic: https://www.hifiengine.com/manual_library/sony/str-vx550.shtml
Little more troubleshooting info:
Both the key lines into IC301 are held at 1V. When I press the up volume I get a little wobble in the voltage of about 0.2V. Nothing happens on the volume down key line. Looking on the oscilloscope I have the same 100Hz 3.8V signal on both lines. On pressing volume up I see two peaks appear on the working line. Nothing on the bad line.
Measuring over the volume down button pad looks like I see a 300mV signal when closing the switch. So looks like the button switch works but no signal getting to the chip. Bad cable? Bad connector?
Further updates: Found the issue. Broken solder joint where the key line for those buttons leaves the switch board onto a cable to the board with the processor. Looks like it just needs to be re-soldered.
Even more updates: Took off the button switch board. Looks like all the wires off that cable were holding on by a thread anyway so I'll just re solder all the connections. Not sure what happened. Seems like the front of this unit got wet and maybe there's been some corrosion.
One last update: reattached all the cables and tested. Buttons are all working again!
This one is going into my 1980s Sony stack. Love the look of these.
Last edited:
