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Quadra 840av never gets to Happy Mac (grey screen with working mouse)

uliwitness

Active member
Hi,

I was hoping someone here could help me revive a Quadra 840av. It seems fine, apart from the power LED being missing (the socket on the main board is there, but there is no LED + cable behind the transparent plastic), but I can't get it to boot through.

When I boot it, I get a proper startup chime, and then I get a grey (black/white checkered) screen with the standard black mouse arrow. I can move the mouse and the cursor moves, but the screen stays that way, it never shows a Happy Mac or "Welcome" dialog.

Very rarely, I get a black "Sad Mac" screen instead with code 0000000F 00000003 which the web tells me is an "Invalid Instruction".

Suspecting that one of the hard disks had died, I popped in a MacOS 8 CD I had around and held C during startup. That didn't change anything either. I also tried a 7.6 CD from a 20th Anniversary Mac, and a CD I burned myself (used Mac OS X Catalina's Disk Utility's Convert menu item to turn the ~24MB .img into a .dmg, then burned that using Finder's "Burn" menu item). Neither of these had any success, still only the grey screen.

I also popped out the motherboard (which showed no obvious traces of leaking capacitors as far as I can tell, but maybe I missed one) and replaced the clock/PRAM battery. No difference, even after doing a PRAM reset using Cmd+Alt+P+R.

Anyone have experience with something like this? Any other things I could try to revive this amazing machine?

Thanks,
-- Uli
 

mrojas36

Member
I revived a Quadra 660av with even more severe symptoms: chime, gray screen but with garbled mouse pointer and artifact-ing when moved. It required a recap, inspection under a microscope for trace damage, followed by trace repair. On my board the pins on the PSC had corroded because of all the leaky caps in that area. It required me to remove that large chip, clean the pads, and resolder back on. Works like a champ now. Can you get some good pics of your motherboard? Maybe we could spot something.
 

demik

Well-known member
Some Quadra AV boards do this if the SCSI chains is not correctly terminated

My 840av board for example, is stuck at the checkered screen if no SCSI devices are connected.
 

Byrd

Well-known member
Hi Uli,

Amazing machine but any 840AV still alive will need a recap - especially when most caps are around those fine pitched custom ASICs. Regardless of whether or not they are leaking (or cap goo has dried out), all 840AV machines need attention and a deep clean of the board.

Of course, do the usual troubleshooting first to see if you can get a flashing ? - switch RAM, disconnect SCSI devices, check PSU voltages

Good luck

JB
 

cheesestraws

Well-known member
When I boot it, I get a proper startup chime, and then I get a grey (black/white checkered) screen with the standard black mouse arrow. I can move the mouse and the cursor moves, but the screen stays that way, it never shows a Happy Mac or "Welcome" dialog.

Have you actually unplugged the suspect hard disc? SCSI HDs can fail in such a way that they just hog the bus and nothing else will work, you can't boot from a CD or another HD either—I've had a couple that did that and that is exactly the symptom I saw. Obviously there are other reasons it can happen as well, but to start with I'd suggest unplugging all the SCSI devices and seeing if you can get to a blinking question mark.
 

uliwitness

Active member
I've unplugged all hard disks, though not the CD or floppy drive. There also seems to be an SCSI card in the Quadra (FWB PowerSCSI or something like that? I'd have to pop it open again to check). But thanks, that's a good point, I may be able to poke around in SCSI-related areas some more. Not that I have any SCSI terminators around right now.
 

uliwitness

Active member
I wouldn't know where to start doing a recap. Any tutorials you can recommend? My soldering skills ended at connecting model train cables, so I wouldn't know what capacitors to buy (nor would I probably be able to tell half of them from especially big diodes).

Now that you mention it, I did get a one-off empty floppy disk icon, but never the flashing question mark inside it. It might have just hung at that point.

I'll also check if removing some RAM does anything (I don't have replacement RAM anywhere).

And PSU voltage ... I wouldn't know what to compare it against. I'd also have to buy a voltmeter I presume.
 

trag

Well-known member
Imagine the 840AV board is a train layout. The surface mount electrolytic capacitors that need replacing look like silver storage tanks. Cylinders sitting on their flat ends. The ones about 1/4" in diameter will mostly have 470 written on top. Probably some thinner 10s around too.
 

joshc

Well-known member
I wouldn't know where to start doing a recap. Any tutorials you can recommend?
Yeah, this guy: https://youtube.com/branchuscreations - he has tutorial videos and just general recapping videos, you can learn a bunch from watching his technique.

Get the basic equipment, a cheap multimeter will do for measuring voltages.

For doing SMD work, a cheap/average SMD rework station that will give you a temperature controlled soldering iron will do the job. I got mine from Amazon. You dont need hot air to do a recap job.

Recapping guide that tells you which capacitors to get for 840AV here: https://recapamac.com.au/quadra-840av/

But, most important of all, do not practice your soldering technique on your 840AV - get some cheap boards from ebay to practice with instead, or use broken junk you might have lying around to practice on. Don't practice on a machine you want to save!

Otherwise, send your board off to a recapping service. Good luck with it, please report back with how you get on.
 

bdurbrow

Well-known member
Probably obvious; but: make sure you have an anti-static mat, wriststrap, and a good grounding point. My kit is grounded thru a built-in safety resistor (1 Megaohm - keeps you from getting badly shocked if you happen to brush up against something electrically energized) and attached to the ground on the closest power outlet (which I have verified is good). Unless the mat is a ESD-safe silicone one, be careful where you put the iron - regular non-silicone rubber will melt and stink something awful.

If there is an e-waste recycling location near you, you might be able to get some practice boards there without having to pay for them from eBay. Likewise, an independent repair shop would likely have a bunch of unfixable ones that already have had the usable parts on them removed, but still have caps & chips that you could practice on. Or, ask your friends if they've got broken routers, radios, etc sitting in their closet or attic that they'd like to get rid of.

Iron tip size: unless you absolutely need to squeeze it in someplace small, use a big one. I use a T12-style iron (T12 tips have a heater module that's bonded to the tip, and gives better heat performance) with the largest "hoof" style tip they make (literally - the tip looks like a horse's hoof, only about 5mm in diameter); even for soldering down tiny 0805 chip caps and resistors. A big "chisel" or "screwdriver" style tip also works. The larger the tip, the more heat capacity it has in it, and the better it can heat up the joint without overshooting the desired temperature.

Use good flux: There is no such thing as too much flux. Go ahead and submerge the joint in flux, it will make the solder flow MUCH better. I'm using ChipQuik paste flux (comes in a syringe) because it doesn't stink too badly, and it cleans up nicely with 99% isopropyl. There are other
brands and formulations that work out OK also, though.

Keep your tip clean: the soldering station will probably include a sponge that you're supposed to keep wet, and use to clean the oxides and junk that builds up on the iron's tip. It works, but doesn't last very long. Instead, I would suggest getting one of those brass tip cleaners (the kind that looks like a scrubber for pots and pans in the kitchen). Not only do they last longer, they put less thermal shock on the iron (because, obviously, it's not wet).

Keep the iron coated in solder (also known as "tinned"): not only does this keep oxygen away from the surface of the tip, prolonging it's life, but the little bit of solder acts as a thermal bridge to allow the heat to flow from the iron into the parts being soldered.

Magnification: Even a little bit helps a lot. At least, get a desk magnifying glass and some bright lighting where you're working. Personally, I spent the $$$ and bought a stereo microscope; but you don't have to go that far.

;)
 

uliwitness

Active member
Yeah, this guy: https://youtube.com/branchuscreations - he has tutorial videos and just general recapping videos, you can learn a bunch from watching his technique.
Thanks, will check that out!
But, most important of all, do not practice your soldering technique on your 840AV - get some cheap boards from ebay to practice with instead, or use broken junk you might have lying around to practice on. Don't practice on a machine you want to save!

Otherwise, send your board off to a recapping service. Good luck with it, please report back with how you get on.
Yeah, thinking I'll check out the local hackerspace to see if they have anyone who's done this stuff and will let me watch while they do it, so I can learn.
 

uliwitness

Active member
Magnification: Even a little bit helps a lot. At least, get a desk magnifying glass and some bright lighting where you're working. Personally, I spent the $$$ and bought a stereo microscope; but you don't have to go that far.
Thanks for all the tips!
 

cheesestraws

Well-known member
Yeah, thinking I'll check out the local hackerspace to see if they have anyone who's done this stuff and will let me watch while they do it, so I can learn.

See if you can get some people to give you dead boards; I practiced on some old routers and a couple of old generic PC motherboards.
 
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