IIcx no boot - missing ROM sim

[Melkhior]

@solidpro You'd be looking for basically a VGA(-like) set of signals, just with slightly different timings due to a higher frame refresh rate. Those signals are documented online, e.g. https://xess.com/blog/vga-the-rest-of-the-story/, the pinouts is on e.g. https://allpinouts.org/pinouts/connectors/computer_video/apple-macintosh-video-15-pin/.
So you'd be looking for the sync pulses (vertical and horizontal) on the separate and composite lines to see what exist (or not!) and looking at the colors to find the vertical blanking and if there's a pixel-clock-rated change of values; you should also see some sync pulses on the green line if the video outputs sync-on-green. The goal is just to see if the video output is alive. If there's no detectable synchronization or color signal, then the hardware has an issue. If one or more are missing, then maybe it's normal (i.e. no separate sync but composite sync or s-o-g is present), maybe it's a hw failure.

 

[solidpro]

Sorry, I just realised the PSU outputs into an inaccessible place when switched on. Can I trace the voltages from one of the connector ports on the back of the case (like on a Plus)?

Thanks

 

[solidpro]

Right. I'll admit something now. I bought a £300 oscilloscope (Rigol DS1054) for this exact kind of troubleshooting, but I've never actually learned to use it. I thought it would be a case of probing the pins on a VGA connector (such as 1/2/3 for R/G/B or 13/14 for H/V sync) and then scaling to the right voltage and frequency, seeing a square visual and then doing the same on the nubus card. However I can't seem to get a decent lock on any pin of either. Has anyone actually done this and has any idea of what I am missing. I probed a few random chips on the IIcx and got the kind of visuals I was looking for (a 'block' kind of freqency for on/off) but I can't get anything on a 'known good' VGA output on a Dell PC I have laying around, nor the nubus port....

 

[joshc]

The IIcx schematics were drawn by Bomarc and are available here:

Macintosh 68k Schematics : Bomarc Services : Free Download, Borrow, and Streaming : Internet Archive

Macintosh 68k Schematics========================Bomarc Services reverse engineered several Apple Macintosh computers in the1990s and sold the schematics to...

archive.org

From that you should be able to tell where you should see 12v and 5v.

 

[solidpro]

Ok so learned a bit about using the scope. There is definitely a lot happening on most of the video socket pins. I'm having trouble comparing them to a VGA output but they're definitely similar. I did successfully lock onto various pins on some of the mainboard's ICs and can see stable digital signals. Most, if not all of the video signals are nothing like these, and i can't seem to get a lock on, but if the main thing is that 'stuff is there' then definitely stuff is there.

So I'm leaning towards it being an issue with either the monitor or the monitor cable (especially as ppl on youtube seemed to have issues getting a IIcx to output to a vga monitor using an adaptor.

I have a bunch of compact macs but I don't think any of them have an external monitor output on board. Maybe I can try and pick up a cheap LC or something to test the monitor with.

 

[volvo242gt]

Or, find a newer RasterOps, Radius, SuperMac, etc, video card that is more compatible with VGA monitors... Seen some decent newer cards on the 'bay for $35-$70... Search for 'nubus video card'.

 

[solidpro]

I found a Performa 475 with a bluescsi HD which is a great little 030 machine with the same video jack on it, so I am going to compare the video on that to this one (and test the monitor). Also a handy 'mystic' upgrade if ever desired...

 

[Daniël]

I found a Performa 475 with a bluescsi HD which is a great little 030 machine with the same video jack on it, so I am going to compare the video on that to this one (and test the monitor). Also a handy 'mystic' upgrade if ever desired...

The 475 is an (LC)040 machine, not an 030. It also does not use the slide-in motherboard of the LC 5xx and Color Classic, so it cannot be used for the Mystic upgrade.

 

[solidpro]

Ah, my mistake. Still a nice quick 68x machine!

 

[volvo242gt]

Apple made the LC line a bit confusing beginning in 1993. Originally, a LC computer was the thin pizza box machine that was sold as the cheapest color Mac, hence the "LC" which stood for Low Cost. In late 1993, the LC line became the educational institution branch, which is why what would've also been known as the LC 475, but for the office/professional branch, was known as the Quadra 605. The LC 5xx series was basically a Color Classic with a larger monitor and a CD-ROM drive added, plus stereo audio, IIRC. Those are the machines that can donate their motherboards to the Color Classic machines. Then you have the LC 630, which is a completely different machine.

So, your confusion is understandable. Had a Performa 475 a few years back. Was the only '040 machine that would run the old Arkanoid game. Everything else, that was newer than a 68000 machine, I tried it on would cause the game to crash.

 

[solidpro]

Thank god for that, because Arkanoid was the first thing on my to-do list...

 

[volvo242gt]

lol

If you're serious, make sure 24-bit addressing is turned on, and I would run either 7.1 with the LC 475 enabler or regular 7.5. Either hold the shift key down when booting, or run a minimal extensions set with either Extensions Manager or Conflict Catcher. That way, there's as little software loaded as possible when playing. Probably set the Monitors control panel to Black & White.