Recent content by JeffC

You could run it without the video board and see if it still freezes, that would narrow it down to the CPU board or video board. I built a USB -> serial cable that I used to run my machine without the video board, using my Windows PC as a terminal.

Yeah the PSUs in these machines are complex. My other SGI is an Indigo2 Impact, and their PSUs are known to be quite problematic. The I2 PSUs are failure-prone, and from what I have read online, essentially unrepairable. Or more accurately, no one has put the necessary time and effort into...

I think this is solved. I ran two test leads out of the PSU, one connected to the 12V rail, and one to GND, so I could measure actual voltage at the PSU. Sure enough the PSU was generating a good 12.3V, but I was still only getting 2.2V measured at a drive connector on the backplane. I took a...

I have tried with two known-good PSUs, and the symptoms are the same with either. Both PSUs also output 12V fine when bench-tested outside of the Indigo. While I can't 100% rule out a PSU issue, I would be very surprised if both PSUs failed in a way that cause the same symptoms.

Hi all, I am troubleshooting an IP20 Indigo (R4400/Elan) that was working until a couple months ago. Current symptoms on power-on are: Orange LED No startup chime No drive activity I do get video output, and after startup I receive a “no keyboard connected” message despite a known-good...

The difference is just the "package" type. PGA and PLCC are the two 68882 package types I have seen, though there may be others. I believe the chip in your photo is a PLCC package and not QFP. The legs on a PLCC package extend out the side and curl back underneath the chip, pins on a QFP package...

You can use a 68882 in place of a 68881, for instance in a Mac II, as long as both chips are the same package (PGA).

Thanks, that's all I'm looking for 1,280 x 1,024, 17" ideally. I'll check with my local Seattle retro computer FB group and see if anyone has one laying around.

Thanks for the info, those look readily available on eBay for semi-reasonable prices.

Thanks for the info. Yes that's the cable I was looking at. I think my best bet is to try to find a monitor that can do SOG, I know some of the NEC multisync flat panel displays can. I don't know how much luck I will have tracking one down though. That adapter you mention looks like a good...

Wow that's a great blog post, I just gave it a quick skim, I'm looking forward to sitting down and reading through it. You weren't kidding about "just restored", the post is only two days old. I'll look into recapping the PSU, looking at the link in your blog post it doesn't look terribly...

Recently I ran across a couple SGI machines for sale, and despite the fact I really don't need them, and don't have a compatible monitor, I went ahead and bought them. I always marveled at SGIs as a kid in the early 90s, but of course saying they were cost-prohibitive is an understatement. 20+...

I was able to fix my board, I'm not sure what the original problem was, probably related to the ALS245s. The final issue I was able to fix was related to poor installation of the replacement RAM chips. I did not have a lot of experience soldering PLCC-package chips at that time, and there were...

Just a heads up there is a 128k/512k HyperDrive controller board just listed on eBay. Since a Plus controller works on my 512k, it may work the other way around with the 512k controller on the Plus. If you can pick it up for a good price it may be worth having in your parts bin as you work on this.

Is there any reason not to prime and paint the bracket, after masking off the posts that solder to the PCB and the little ears that connect to the chassis?