VOGONS


First post, by seanneko

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Does anyone here know much about SPARCstations? I have a SPARCstation LX in the lunchbox form factor which I'm having issues with.

I picked it up in broken/as-is condition. The power supply is pretty much shot due to leaking capacitors which have eaten away at the traces. The motherboard looks fine though and has no obvious damage. I wired up an ATX power supply with what I'm pretty confident is the correct pinout from the official Sun service manual. The only pin I was unsure of was labelled as "POR" on the Sun motherboard. This appears to be a power good signal, but there's no indication of what voltage or signal it expects. I wired it to the power good pin from the ATX power supply which puts out +5v.

After powering up, I don't get any signs of life from it. Poking around the motherboard with a multimeter seems to show the correct voltages on different components, so I'm reasonably sure (but not 100% sure) I've done the power supply right.

If I power up with a compatible monitor and a Sun keyboard connected, the monitor never shows a signal. If I unplug the monitor and keyboard, connect a RS232-USB adapter to the serial port then connect into the serial console, I get no output from it.

Does anyone have tips for troubleshooting one of these things? Are they known for just totally dying like this?

Reply 2 of 9, by seanneko

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derSammler wrote on 2020-03-26, 08:19:

I think you need to make sure the ATX PSU is wired correctly first. There's a video on YouTube about the conversion: https://www.youtube.com/watch?v=c8ZPXvgC23Y

Yeah, I saw that video. It's pretty hard to make out exactly what he's doing, but I'm fairly confident I've done the same thing as him. It matches up with what the Sun service manual says too.

Reply 4 of 9, by seanneko

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When turning on the speaker does make a sound, but I wouldn't call it a beep. It's more like a pop. So something is clearly not right.

I didn't realise that the serial port was RS-423 by default. Is it possible to change it to RS-232 when I can't get in and reconfigure anything in software?

Reply 6 of 9, by seanneko

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There's only one set of jumpers on the entire motherboard, and it's to do with ISDN termination. No way to change the serial port (at least not via jumpers).

I haven't been able to work out whether the serial port is RS-232 or RS-423. The documentation is pretty poor. The service manual has one reference to RS-232 and no references to RS-423, so maybe that means the SPARCstation LX uses RS-232. I'm not entire sure though.

Reply 7 of 9, by seanneko

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Yeah ok, I'm an idiot.

I checked the voltages on the ATX PSU I'm using, and it only had 3.6v on the 5v rail. The SPARCstation is such a low power machine that it wasn't even drawing enough load to bring the voltages up correctly.

Hooked up a HDD to the PSU to draw some additional load, and the computer came to life. It works perfectly now.