Color Classic motherboard woes

[This Does Not Compute]

I'm picking up a project I've been sitting on for some time. I have a Color Classic that doesn't want to boot. When I press the power key, the light will come on and the hard drive/fan will spin up, but there's no chime or image on the CRT. It's definitely not trying to boot because I'm not hearing any attempts at seeking/activity from the hard drive.

We'll call this machine System A. I have another CC, System B, that overall works fine. If I put B's motherboard into A's chassis, everything works fine. Out of curiosity I put A's motherboard into B's chassis, and it still doesn't boot, *except* that the CRT lights up to a grey screen with obvious raster and no mouse cursor. (B's analog board needs a recap, but the image doesn't look this bad when B's motherboard is installed.)

A's motherboard is clearly the culprit here, but I'm scratching my head as to where to go next. There's nothing in the RAM or VRAM slots, and the board was recapped already (with tantalums) before I got it. It's also spotlessly clean, with zero signs of corrosion or battery leakage. I took a look at all the chips under the microscope to check for shorts/bridges but I'm not seeing anything obvious.

What would you do? Recap the board again? Any specific points on the board I can check with a multimeter/scope?

 

[Fizzbinn]

Do the grounding metal springs on motherboard A look good, the same as motherboard B? None missing, all making good contact with the bottom metal shield? Your description is giving me deja vu in my own Color Classic troubleshooting a couple years ago which I think I fixed by fixing a grounding contact issue.

Desoldering the EGRET chip, cleaning under it and resoldering also seems to be popular advice...

 

[nyar]

Hey!

I had a similar issue with my machine. It would sometimes not show a display or show a blueish screen, sometimes give sad mac chimes. I couldn't get it to boot. It sometimes wouldn't turn on at all. The issue for me ended up being two vias near the battery that were not making a good connection. Despite looking okay visually, they were damaged and did not have good continuity. After jumping them, the board fired right up. Maybe check around the egret as well as near the battery for continuity.

 

[ComputerCompulsive]

I have a color classic board with the same behaviour. It's currently with Amiga of Rochester for diagnosis and repair.
The suggestion I had been given on the forums before sending it off was to try an ultrasonic clean and try removing, cleaning, the cuda chip if the ultrasonic cleaning didn't change anything.

 

[retr01]

@YMK!

 

[YMK]

I'm no expert, but I'd reflow the edge connector.

Since you have a spare board, maybe swap the Egrets if you've got the gear.

 

[This Does Not Compute]

Well, I removed the EGRET chip and found some electrolyte residue underneath but no trace damage. Got it cleaned up and resoldered the same EGRET back on, but no dice -- the problem persists. I'm not willing to swap the EGRET from my working board, so I'll need to find a donor or see if UTsource has any left...assuming that chip is actually the problem.

I'll take a closer look at the edge connector under the microscope.

 

[Elemenoh]

I'd suspect the EGRET too. Have you tried leaving the machine powered up for a while? I've found that some will eventually boot if 'warmed up' for 10 minutes or so.

 

[wottle]

I'd suspect the EGRET too. Have you tried leaving the machine powered up for a while? I've found that some will eventually boot if 'warmed up' for 10 minutes or so.

I had similar experience with a machine that was having trouble booting. The main difference in behavior was that I wasn't getting any lights or any signs of life. Left it plugged in and on overnight, and it booted fine the next day. This feels like a different issue.

 

[tms9900]

The fact that the system powers on to some degree (fan/drive spinning) indicates that the CUDA, referred to here as the EGRET, is likely fine. Would be a different story if the system wasn't responding to the power button on the keyboard at all. The motherboard grounding springs should have no effect on booting on an original Color Classic board, as all the springs are tied together on the board itself (what kind of impact they'd have on each different kind of LC5xx board in upgraded/Mystic systems, I am not sure).

Out of curiosity I put A's motherboard into B's chassis, and it still doesn't boot, *except* that the CRT lights up to a grey screen with obvious raster and no mouse cursor.

I have run into this exact issue with the gray screen, no chime/cursor on a CC board with bad solder joints on the DFAC II IC. The issue seemingly not manifesting itself on your "System A" in the same way could be due to differences in how the two systems' monitors are adjusted. Was able to confirm the DFAC as a culprit when I pulled one off a working CC motherboard; running that board without the DFAC caused it to show the gray screen symptom as well.

Try pulling the DFAC, cleaning the pads and underneath it if necessary, and soldering it back down. If the cap damage prior to recapping was severe, the leads on the IC may have tarnished, and with this particular style of IC can become slightly more difficult to solder properly. If it still doesn't work afterwards and you have access to a schematic, check all the connections on the DFAC, especially the ones between the DFAC and CUDA. Probably worthwhile to check the ones between CUDA and Spice/RAMDAC as well.

 

[This Does Not Compute]

The fact that the system powers on to some degree (fan/drive spinning) indicates that the CUDA, referred to here as the EGRET, is likely fine. Would be a different story if the system wasn't responding to the power button on the keyboard at all. The motherboard grounding springs should have no effect on booting on an original Color Classic board, as all the springs are tied together on the board itself (what kind of impact they'd have on each different kind of LC5xx board in upgraded/Mystic systems, I am not sure).



I have run into this exact issue with the gray screen, no chime/cursor on a CC board with bad solder joints on the DFAC II IC. The issue seemingly not manifesting itself on your "System A" in the same way could be due to differences in how the two systems' monitors are adjusted. Was able to confirm the DFAC as a culprit when I pulled one off a working CC motherboard; running that board without the DFAC caused it to show the gray screen symptom as well.

Try pulling the DFAC, cleaning the pads and underneath it if necessary, and soldering it back down. If the cap damage prior to recapping was severe, the leads on the IC may have tarnished, and with this particular style of IC can become slightly more difficult to solder properly. If it still doesn't work afterwards and you have access to a schematic, check all the connections on the DFAC, especially the ones between the DFAC and CUDA. Probably worthwhile to check the ones between CUDA and Spice/RAMDAC as well.

The area around the DFAC looked clean, but I went ahead and desoldered it to clean underneath anyway. I soldered it back down and unfortunately I'm still getting the same results. I've started testing for connectivity from both DFAC and CUDA, but the Bomarc schematics suggest there's only two lines between those two and they test out good.

One thing I did notice is that pin 24 on DFAC, according to the schematics, is labeled RST (presumably "reset"?). When I test between that pin and ground, I'm getting just under 2k ohms. On my known good CC board, though, I'm getting 3.6k. Could this be a factor?

 

[retr01]

It may be a factor if 2.6k ohms is out of the threshold required to boot up through that point. See what you can to return around that 3.6k ohms?

 

[tms9900]

When I test between that pin and ground, I'm getting just under 2k ohms. On my known good CC board, though, I'm getting 3.6k. Could this be a factor?

Personally I doubt it, there tends to be a fair bit of variation in these readings between individual boards. A surefire way to test would be to measure the voltage on that pin: after pressing the power button on the keyboard, it should read 0V for a little under one second, then jump up to roughly 5V.

Easiest way to measure it would be to solder a reasonably long wire to the RST# pin (whether it be at the DFAC or the CUDA), stick it out the back of the computer, sliding the motherboard into the chassis as normal, and then measuring the voltage from the other end of the wire (with the negative lead of the multimeter being on any of the port shields).

If the voltage on that pin/wire transitions from 0 to ~5V, you can be fairly confident that the CUDA is operating correctly, and that nothing connected to RST# is actually shorted. Failure of the DFAC IC is uncommon but not unheard of.

One other thing to try now that you have the DFAC reinstalled: when the CC is stuck at the gray screen, try triggering an NMI from the keyboard (key combo is Command+Power IIRC). If that causes it to play the death chimes, it would confirm that the CPU is executing code from ROM and able to talk properly to the Spice IC (big ASIC).

 

[JDW]

While I am on some level curious what the ultimate fix for that stock CC motherboard will be, the opening post also flat out asked: "What would you do?"

I personally am curious if the sheer slowness of that stock motherboard makes a time consuming repair worthwhile in the end. Purists literally hate me when I say this, but I shall nonetheless... An LC550 motherboard will transform it into a Color Classic II (which is technically semi-pure), and yield a much more usable machine. Of course, going full board to an LC575 board will tick off the purists (even though it may have been pulled from a destroyed machine), but the power of the LC575 board will trigger sheer delight every time you power on, especially with Spicy O'Clock and fast 60ns VRAM help from @Kay K.M.Mods.

I will admit that I have a functional stock CC board which I retain in my collection for one main reason. Should I ever change my standard VGA mod to the High Resolution VGA mod some day, which will give me compatibility with the original CC board, I can always swap in that stock board to show people just how painfully slow it is! Seriously, there is good reason why so many have used the LC550 or 575 boards (mainly from plastic-case-destroyed machines) to make the CC more fun and usable. It's still worth repairing your stock CC board, I guess. But for a daily driver, nothing beats the joy that comes from a fast 68k machine. Mine beats a Quadra 840AV in many respects!

 

[This Does Not Compute]

I personally am curious if the sheer slowness of that stock motherboard makes a time consuming repair worthwhile in the end. Purists literally hate me when I say this, but I shall nonetheless... An LC550 motherboard will transform it into a Color Classic II (which is technically semi-pure), and yield a much more usable machine. Of course, going full board to an LC575 board will tick off the purists (even though it may have been pulled from a destroyed machine), but the power of the LC575 board will trigger sheer delight every time you power on, especially with Spicy O'Clock and fast 60ns VRAM help from @Kay K.M.Mods.

This is a very valid take on the situation, and I've definitely considered just turning this machine into a Mystic and being done with it. The problem for me is one of economics -- the Mystic mod seems to be even more popular now than it was when it was new, but the prices for LC 575s (or even just their motherboards) are an order of magnitude higher now than they were back then. Even LC 550s aren't cheap, and in my case, I don't need another CC II/Performa 275 anyway. This particular CC is in very good overall condition (just a bit of yellowing) and, aside from this particular issue, the board is pristine. My strong preference is to try to restore the machine to stock if, for no other reason, then to preserve it as an example of what the Color Classic actually was.

 

[JDW]

This is a very valid take on the situation, and I've definitely considered just turning this machine into a Mystic and being done with it. The problem for me is one of economics -- the Mystic mod seems to be even more popular now than it was when it was new, but the prices for LC 575s (or even just their motherboards) are an order of magnitude higher now than they were back then. Even LC 550s aren't cheap, and in my case, I don't need another CC II/Performa 275 anyway. This particular CC is in very good overall condition (just a bit of yellowing) and, aside from this particular issue, the board is pristine. My strong preference is to try to restore the machine to stock if, for no other reason, then to preserve it as an example of what the Color Classic actually was.

About one month ago, a kind person based in Europe contacted me to say that the LC520 he ordered from Yahoo Auctions Japan via Buyee arrived in Buyee's hands completely destroyed (case plastics broken apart, despite great handling by Japan's postal system), so he wanted to donate the broken parts to me because he already lost money on it and he didn't want to spend a large sum shipping broken pieces to Europe. I knew it would arrive broken apart, but I was hoping the motherboard would be intact, and it was. Sadly, I cannot test that board yet because I have the standard VGA mod installed in my only CC. The LC520 is the same as the stock CC board in that it requires either unmodified stock graphics or the High Resolution VGA mod. Even so, the 520 board looks very clean and undamaged.

Anyway, Yahoo Auctions Japan was how I got my LC575 board, for ¥9,250 (US$68 at today's rate), which included domestic shipping within Japan. That otherwise fully functional LC575 machine didn't arrive unscathed, although it wasn't broken to pieces like the LC520 machine. Even so, when buying a LC500-series machine from anywhere these days, the plastics will most likely not survive, due to the sheer weight of that CRT.

By the way, I also picked up a Performa 630 for only ¥4000 (US$29) shipped (within Japan), which I show that in this timestamp in my Stereo mod video. Interestingly, that machine didn't have the stock 68K motherboard. It had a PPC board in it, and I donated that board to someone who needed it. I only bought it to extract the speaker, since I knew the condition of the machine would be bad, and it's not one of the more highly prized vintage Macs either. Plastics were as brittle as an LC500-series, but the metal chassis keeps everything inside protected.

The reason I told you all this is because EBAY prices are insane, while Yahoo Auctions Japan seems to sell things at reasonable sums. The only way to get an even better deal would be a yard/garage sale or perhaps a Goodwill in the US.

 

[Mu0n]

Yahoo Auctions Japan prices are surprisingly good and makes me think about 1999-2005 era ebay prices but the shipping just slays us if we don't have the same privilege as someone living in Japan and not require international shipping. My "sealth" Color Classic II (advertised as CC1, but actually containing a LC550 logic board) cost me $230 CAD to ship, surpassing the price of the machine itself greatly. It's been great to have it all refunded, except the warranty price when it arrived with a sizeable crack in the top front corner and still get a few days of usage out of it before it got to WEIRDO LAND OF IRREPRODUCIBLE RESULTS

 

[This Does Not Compute]

I'm well-aware of Yahoo Auctions Japan, I've bought a *lot* from there over the years ;-) The difficulty is shipping -- if I were in Japan it would be a no-brainer to pick up what I need from there (or even just keep an eye on shops like Hard-Off) because domestic shipping is economical and very good. International shipping, though, is not. Case in point: While I was able to buy my Performa 275 for $80, shipping it to the US cost over $200. I'd estimate that with its additional size and weight, an LC 5xx system would probably be closer to $300, in addition to the $150 or so that the system itself would sell for. Suddenly, $400 for a 575 board from eBay in the US starts to make sense, especially considering that I've noticed Yahoo Auctions prices have been steadily rising (likely from overseas buyers).

 

[JDW]

The current exchange rate is in the favor of those outside Japan, with today's rate being ¥136 to US$1. Furthermore, Japan Post still offers low cost ocean shipping, unlike USPS which killed it off way back in 2007. I purchased a number of heavy vintage items from the US back in those days and was able to cut costs by being patient. It took a couple months for delivery, but I saved a bundle. I remember when my father sent me a Weber BBQ, long before they started selling them here in Japan, made possible with ocean shipping by USPS. Not sure of Buyee offers that, but if it does, and if you're patient, it's much cheaper (and slower) than costly air freight.

The maximum weight limit for ocean shipments is 30kg/66lbs. Shipping that weight from Japan to California by EMS (express Airmail) costs a whopping 75,100 Yen (US$551), while ocean costs 20,900 Yen (US$153). Most vintage items won't weight nearly that much. An LC575 weighs 41lbs/19kg. That weight costs 14,300 Yen (US$105) by ocean. Obviously, it would need to be packed well.

The best solution would be if you could buy the item only for the motherboard, then get the seller or shipper to remove the board, pack the board, and discard or donate the machine, thereby reducing shipping costs even further.

Here's the Japan Post web page to check rates:

郵便局 | 日本郵便株式会社

Use the post office for overseas shipment.

www.post.japanpost.jp

 

[lfletche]

If you find a solution to this Colin I would love to know - A few weeks ago I recently got a Colour Classic that was totally dead. Ultra-sonically cleaned and recapped it and it sprung to life and started working perfectly. I ran it for about 6 hours over the course of a couple of days to make sure it was running well / stable. Then today when I turned it on to test it again (had not even moved the CC from when it was last working) I was greeted by the problem you describe here - powers on, but just stays at a grey screen - no chime, no mouse, no booting. :-( Tried it in a different case/analog board - same issue.

I actually hit this problem last year with another CC logic board and I never managed to solve that one. I pulled that board out of storage today and it now seems to have gone back to the "not even turning on at all" problem. These CC boards kinda have me scared every time I turn them on.

Anyway, I spotted your post while searching for solutions this evening, so I feel your pain, and keen to hear if you find a solution!