[Irinikus]

Maybe there was a very big short in the system, leading to an extreme current draw!!! Everything has its limit.

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Maybe the motherboard was pulled while the power supply was still energised!!!!! (Plugged in!!!)

[weblacky]

I also see where I misread the label. Looking very close, there are pads for a missing C77...right above the C77, so the actual PPTC label was U1. So that's my first mistake, didn't observe the missing component and assigned the wrong label to the it's neighbor. OK, still haven't yet tracked down a match for this little guy.

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OK, I think I found them:

Raychem SMD150-2 POLYSWITCH

Raychem was purchased by TE, the part has been obsoleted (but many are on ebay). This "packaging" of the PPTC is now used for higher voltage parts. This part (in its new form) appears to have been shrunk. Which explains why I've been fighting to find a "modern" version with the same markings. Time has moved on and these specs can be handled by smaller packages. Only large currents need this form factor now.

Buy old stock from eBay to fit the foot print. Parts are from the very early 2000's and very cheap.

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Serena,
Could you tell use what peripherals you plugged in when you powered it up?  Like exactly what you plugged in, model info if possible.  It seems these fuses are often sold to protect IO ports and telecom interfaces.  I assume you plugged in a normal Sync-On-Green VGA monitor.  What else, did you happen to use any kind of adapters?  The O2 is a PS/2 system.  Did you have some kind of USB -> PS/2 converter.  Did you plug in Ethernet?  What about external SCSI?

I'm trying to see if there was anything unusual about what was plugged in that might explain this.  If you're handy with a soldering iron, I'd buy some of these Raychem SMD150-2 parts on eBay and after removing the bad one, do a quick Diode check for a short on the pads to GRND and around a bit.  But perhaps something that was plugged in overdrew the fuse? At about room temp this datasheet claims it hold between 1A~1.75A before tripping. This was a lot more, but since it's unknown if it came to you this way, maybe you did nothing and received damaged goods.


If there is no way to return it and you'd like to move forward, trying doing the replacement and see what happens.  Let us know if you decide to remove, test, and install the replacement part.

Raychem SMD150-2 Polyswitch Data Sheet link

[Lady Serena Kitty]

The stuffies I had connected for my first boot attempt:
* Dell keyboard, model AT101W, 5V@275mA
* Cheap mousie, 5V@100mA
* Toshiba TV, works purrfectly with Margay (my Indy)
* Comcast Modem-router combo unit (for ethernets)

On later boots: USB RS-232 adapter (from Adafruit) used with Jaguar (my system76 Gazelle) to read any serial output (there wasn't any).

[weblacky]

When you say TV, what interface did you use? Are doing VGA (like a first-gen HDTV-ready CRT or LCD) or are you using a VGA to composite adapter?

[Lady Serena Kitty]

Toshiba TV has a VGA input, so I'm using that along with a completely passive standard VGA cable. This TV works purrfectly with my Indy and the 13W3->VGA cable (which is also a completely passive cable). I got this TV back in 2010.

[weblacky]

Well, it all sounds reasonable. I can’t find any smoking gun that you did anything incorrectly. I’m more apt to believe you received it this way. Unless it’s a type PSU failure (can’t find any documentation to back that up) or it’s damage caused by disconnecting parts in an incorrect order (e.g. sliding out PSU while still plugged into wall outlet).

So again, what your recourse? Will you fight to return it or get some kind of refund? If that’s not possible, are you open to soldering in a new polyswitch (sourced from eBay) and see what happens?

[Lady Serena Kitty]

There's no refund, as I got the O2 from Raion. Sadly, he doesn't have any other O2 boards to swap with. I can do soldering fine, I've fixed mousies with bad tails.

I think what I'm gonna do is source another O2 board and put this one in storage and wait for you to get the testing equipment in December. That way, we can have more information about the part that went explodey and do a proper repair on this board. Plus, this board's rear connectors are all rusty and I can use the time to replace (or chemically clean) all of those.

[weblacky]

Well, my equipment (if I get it), would likely only be good for comparisons between boards. Since I don’t plan on desoldering my polyswitch, the only thing I could offer is checking for a simple short after polyswitch removal and then comparing readings after the polyswitch is replaced and my board with the same component in-place.

Uhh, rusted ports...my guess would be that’s the real issue. Rust can easily create a “track” and short something. Remember that a system 5v rail comes out of several ports (PS/2 at least), if that rail were shorted at the connector via rust, that could explain any interface damage.

But, I’ll say yes. While I’m not thrilled with using my known working parts as a test subject. My equipment (should I be able to get it), would easily tell me if there was port interface damage, by simple comparison.

Hit me back up in December, buy a good replacement polyswitch (identical) now anyway. If I’m able to help, I will. I’ll just ask for you to cover mailing and any part costs going fourth. Since this is a hobby and an investigation, they’ll be no cost outside of the above materials and shipping.

If the ports are rusty, if I do find something I cannot severe or clean off, I’m unsure I can replace port clusters. It’s pretty challenging and we’d need replacement parts. It’s unknown if those can be found. But as an exercise, it’s worth a shot, versus a landfill.

PM me in December on this topic again.

[Lady Serena Kitty]

So, weblacky showed me an ebay listing for basically an entire O2 system without the casing. Today it arrived and I did a complete system swap. All my parts came out, all the new parts went in.

I plugged her in and .... both red and green lights came on, no video signal. I examined the system board and found no issues. I'm thinking there may be an issue with the backplane. I want to do a full disassembly and pull the backplane board to examine it.

On the other paw, the parts that arrived included an audio card with moar connectors, seems to be an upgraded audio option. I think I'll be keeping that when I go to sell the excess parts.

[weblacky]

The O2 manual claims that a RED LED is registering a fault, however it suggests that there should be an error message (I assume it's implied to be on the serial console). The manual claims a Null-modem DB9 cable should function in that capacity. Hopefully it boots enough to output information that can tell you what it's unhappy about.

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In the meantime, you might want to remove the audio option and as much RAM as you can (layout according to whatever the manual recommends as a minimum) and see if you can simplify the system to see if you can find the issue. I'd also pull all drives (even Optical), boot it diskless until you know what's going on.