Dead audio output on Indy?

[ClarusWorks]

I have an R5000 Indy with malfunctioning audio output. When I power the machine on, I do not hear the startup sound although it boots into IRIX normally. The audio test in IRIX also results in no output. If I connect headphones, I hear some high-pitched whining, and a very faint beeping tone during the audio test. The one thing I do notice is that when I first power the machine on, I hear a pop that sounds like it could be coming from the speaker, and a similar pop when I turn it off.

This machine has a Nidec PSU,which is apparently famous for going bad. I know the speaker's inside the PSU, is the audio amplification stuff in there as well (such that even with headphones I'd get no output)? Any other parts that are likely to be causing this? I'm planning to pick up some upgrades for this machine anyhow - I want to get one of the Sony power supplies and replace the 8 bit graphics card with a 24 bit one, and I also need a hard drive bracket since the previous owner appears to have attached the drive with duct tape.

[ClarusWorks]

I did a bit of further testing tonight, and here's what I observed:

The pop is coming from the speaker. I took the cover off of the PSU and disconnected the cable from the switch/LED PCB to the speaker, and the pop went away. A similar pop is heard in headphones if those are plugged in.
Interestingly, I hear a lot of system noise through the headphones: Buzzing during mouse movements, the sound of the HDD heads seeking, etc. This + the pop leads me to believe that there's a short somewhere in the audio circuitry (the kind of loud pop the speaker is making sounds like what happens when you connect DC to a speaker, and the system noise on headphones sounds like the electrical noise you'd expect to find on one of the DC rails).
It looks like the audio amp for the speaker is on the motherboard - there's a Phillips TDA7056A on the board next to the PROM. Has anyone seen this kind of failure before? I could go probing around a bit, but unfortunately the area of the board in question is directly underneath the graphics card. Will the machine still run and be accessible over serial console with the graphics card removed?

[jan-jaap]

Hi,

I think you're right -- the speaker (and the volume controls) are in the PSU but the audio circuitry in on the mainboard. Are you sure there's nothing wrong with the volume?

An Indy will work fine over the serial port, you have to set the NVRAM (PROM) variable 'console' to 'd' rather than 'g', like this: http://software.majix.org/irix/admin-headless.shtml

You will need a suitable null modem cable with mini-DIN8 on one end.

[ClarusWorks]

Cool, thanks for the advice. One more thing - I'm seeing some kind of crash message at the end of the IDE diagnostics. I've seen this come back every time, and have tried swapping RAM so I don't think it's a bad SIMM. I see GIO bus, so maybe the graphics card? Or maybe it's yet another motherboard fault along with the audio issue. Anyone know what this means? Sorry for the newbie question, this is my first experience with SGI hardware and IRIX.