IIcx no boot - missing ROM sim

[solidpro]

Hi

I've acquired a IIcx in lovely condition. It powers up but no chime and no video. I notice the ROM sim is missing and am guessing this is the issue.

I have various other compact macs laying around as well as a bag somewhere full of left over ROM or ROM-esque boards. Can anyone share a photo of a IIcx ROM SIM or tell me it's part number, or identifying features?

Can I 'borrow' the ROM SIM from a SE/30 of mine to test it?

Thanks

 

[volvo242gt]

I don't really see any reason why not. Back when I owned a IIcx, the ROM was corrupted. I'd get the startup chime, then the sad mac chimes immediately afterward. Dropped in a SIMM from a IIfx into it. Computer worked fine. Essentially became a slow IIci without VampireVideo.

 

[solidpro]

Do you think 'trying anything that'll fit' is likely to do anything other than a no boot?

 

[demik]

IIcx have the ROM on board. It's 4 27C512 like chips near one corner.

SE/30 ROMs do work in a IIcx ROM slot tho. There is a jumper at W1 which is used to select from the Internal ROM or the ROM Slot.

Also a IIcx may behave like yours if the caps are dead.

 

[volvo242gt]

Yeah, it might be worth getting the board recapped, then seeing if the 27C512 chips are ok or not. If it does the usual guitar chord at boot and you get video, great. If it instead does the sad mac chimes, then, grab the SE/30 SIMM and swap it in.

*edit* BTW: the ROM chips are to the left of the RAM SIMMs, just behind the programmer's switch assembly.

 

[solidpro]

I put an SE/30 ROM in and nothing. I saw the W1 jumper but didn't know what it did, so thanks for that. I can pretty easily re-cap it, as I'm familiar with doing so with SE/Classics - does anyone see a reason not to use tantalums as direct replacements for the surface mounted aluminium caps?

thanks all

 

[volvo242gt]

Tants should be fine. Another option is the multiple layer ceramics. But, anything's better than leaky electrolytics.

 

[solidpro]

Ok, so the plot thickens. I have so far replaced all the surface mounted aluminium caps with tantalums (and I'm pretty good now at safely removing, cleaning and re-soldering these now) and now it powers up, no video and 'death chime' (4 tones, rising in pitch).... I've tried with and without an SE/30 ROM.....

 

[joshc]

It should chime without a video card installed.

Can you post some high quality photos of your logic board please?

 

[solidpro]

Right, Ok times are a-changin'.

I switched the ram around and now with 4 original SIMMs in Bank A I get a single, normal chime. Still no video with the card moved between all 3 bus connectors.... the plot seems to point towards the nubus being bad, but the cheapest I can find is 'untested' on ebay for £50

 

[joshc]

What VGA adapter are you using and what have you got it set to, assuming it's one with DIP switches to change the resolution. Also which monitor are you using it with?

 

[solidpro]

I'm testing with both a period-fresh Apple 15" Multiple Sync display as well as one of those dip-style VGA adaptors to an iiyama LCD. Neither ever shows anything.... I have an older dell 4:3 LCD laying around, along with some other LCDs i thought I might try just incase both of these are duds. However I think the CRT should have done it, so now thinking nubus.... It is one of those cards with 8 RAM expansion chips on it (socketed). I was thinking of pulling them off and re-trying...?

 

[solidpro]

Oh and also I have at least 3 of those HD15->DB15 adaptors and all of them do absolutely nothing...

 

[joshc]

Which video card are you using, got photos of it?

 

[solidpro]

I think it just says on the bottom "Macintosh II video card". I pulled the 8 additional socketed chips off and - nothing.
I pulled out another LCD monitor and tried all 3 adaptors i have with the nubus card in all 3 slots and - nothing.

Basically, I think it's the nubus. I guess I'll wait for a cheap, tested one to come up on ebay.

 

[joshc]

Never had one of those cards faulty but I guess it's possible. I wonder if NuBus on your board is broken somehow?

 

[Melkhior]

I think it just says on the bottom "Macintosh II video card"

To check the NuBus device output without relying on a LCD, you could use a logic analyzer to watch the signals (sync, colors) directly on the DB15 plug. It does require some knowledge to use the tools and understand the signals, but even a basic 4+ channels/100+ MHz logic analyzer should be able to tell you if something appears on the pins, and whether that looks like a reasonable set of signals. (the dirt-cheap 24 MHz ones probably won't help as the pixel clock is likely to be around 31.5 MHz, though they might show the synchronization signals).
The same logic analyzer can also be used to see if there's some signals on the NuBus pins, to check it it's the motherboard rather than the device that has an issue - in this case for the 10 MHz NuBus a cheap LA might be enough, but a cheap-but-not-too-cheap one (like a LA2016 clone) is still probably a better tool to have.

 

[joshc]

Another thought is, how strong is the PSU? Check the 5v and 12v rails, are they stable and within tolerance?

 

[joshc]

Also, worth a try - spray the DB15 connector on the video card with contact cleaner. I've had a dirty/corroded conncetor cause video to stop working before.

 

[solidpro]

I'll check the voltages and de-oxit the video cable/connector and report back.... I do have an analyser but have no idea what I'd be looking for on the DB15 plug....