UMC-200 no audio output

[themg]

Turned on the UMC-200 as I usually do to watch a TV show and the sound came through at MAX VOLUME on the front-left channel only, absolutely nothing out of the other channels. Scared the crap out of me, wasn't expecting it.

Changing the volume had no effect, neither did putting the unit to standby and back to on. So I did a hard reset by turning off the power switch on the back for a moment, then back on. After this, now I get absolutely no audio out of any channel, at any volume, regardless of input source. Also, the noise that should be heard when calibrating the speaker levels does not come through either.

This time around, it does not appear to be a power supply issue, all voltages check out ok, all capacitors test good (replaced a couple bad caps on the power supply some time ago, these are still fine).

As far as I can tell, there is audio output from the ADC, so the DSP, ADC, and LPF appear to be doing their thing. From what I can gather the outputs from the LPF boards seem to go to a volume control and input selector chip NJW1298, nothing is coming out from there.

Unfortunately, I can not find sufficient information on this chip to perform any further troubleshooting (not even pinout information). I figure either the chip has given up the ghost, or there is some other issue and it is not receiving the correct serial commands from the processor.

I'm quite experienced with electronic troubleshooting and repair but due to a nearly complete lack of any documentation it makes things quite difficult, I'm left making educated guesses as to what everything on the board does.

Anyone have any knowledge/insight into this? I'd really like to get this unit working again.

[cwt]

Give them a ring ; there is 2 ways to look at intellectual property like this as evidenced here ;

emotivalounge.proboards.com/thread/25661/amplifiers-circuit-diagrams

[themg]

Thanks to a user on the EEVBlog forums that posted a link to the service manual for a receiver from a different manufacturer that uses the same IC, I was able to determine the pinout.

I soldered some wires temporarily to the DATA, CLK, and LATCH pins of the NJW1298 and hooked up my logic analyzer. Waveforms looked perfectly fine.

What happened next is pure luck I guess... it started working again! My theory is that there must have been a faulty solder connection on one of those pins, preventing the serial commands from getting to the IC. Must have been a weak solder joint to begin with and a month ago when I removed the board to check all the capacitors, the stress from this must have cracked that already weak joint.

Anyways, I've reflowed the entire IC with fresh solder and put the unit back together. So far so good. Lets hope it stays that way!