SE/30 with Micron Xceed Grayscale & Socketed Daystar Acceler

[tt]

JDW, it might be easier to explain if you say draw a black or plain white background in hypercard and make lines in the exact locations and mark them. Then you could count pixels. Although it might be tricky to do fullscreen (maybe a really old HC version) since the micron xceed adds an extra pixel in one of the directions.

[JDW]

With a spray can and the little tube it comes with, you should be able to squirt solvent in the hard to reach spots... You could also try the dishwasher method. A soak in hot water will probably get the hidden spots. But....it's also possible that the goo ate a via.

Thank you for the advice. Since I don't have a dish washer (such are uncommon in Japan), I just spayed an enormous amount of Ethanol on the board while it was at an angle to let it drain. At the same time I used a can of compressed air to blast the Ethanol off the board quickly and under chips and connectors. I can truly say the underside of the PDS connector is now very clean! I cannot see the underside of every soldered in chip though. And I cannot help but feel some deep sense of reservation about dunking a PCB in water!

I also pulled the socketed chips as you suggested and I reseated them carefully. I then too the pains to use a continuity checker, touching the top of each pin on the chip with one problem and then touching the other probe to the opposite site of the logic board, proving that each pin was perfectly connected to the board.

And yet, when I booted I again got the sad Mac "chimes" and the horizontal lines, as shown in my new 720p video here (please take time to watch it):
http://www.youtube.com/watch?v=mKJszJMRZM4

Could it really be that gunk is still causing this? If no, what specific chip could have gone bad to have caused this? And keep in mind video is displaying, if not but those horizontal lines, and the audio is good as evidenced by the fact you can hear the chimes of death! So I would appreciate hearing your thoughts on this, as this board is the only other socketed motherboard I have for the SE/30. And I would like to resurrect it, if possible.

JDW, it might be easier to explain if you say draw a black or plain white background in hypercard and make lines in the exact locations and mark them. Then you could count pixels. Although it might be tricky to do fullscreen (maybe a really old HC version) since the micron xceed adds an extra pixel in one of the directions.

I need to get one of my SE/30s in running order and put back together with my MacCon Ethernet card so I can get files out of the machine. I cannot physically insert my MacCon in the Xceed machine, and I don't have a USB floppy drive, which would be the easiest means of getting files off the SE/30 and onto my Intel iMac so I can upload them to the web for all to see. I will work on this over the next 48 hours.

[bigmessowires]

OK, I'm wading into a thread without having really read the whole history, but here are a couple of thoughts:

1. If you suspect a power supply problem, then you might want to monitor the 5v output with a scope, and set it to trigger on anything below 4.8v or so. By measuring with a multi-meter, you won't catch brief power supply glitches. I think a bad power supply is likely to suffer brief voltage droop in an instant of high current demand, rather than a sustained period of low voltage that could be measure with a multi-meter.

2. If you suspect a DRAM or SRAM chip has gone bad, can you try poking at the chips with a probe while the computer is running, and see if you can affect the display in a way that identifies which chips contribute to drawing which parts of the display? Then you might be able to determine which chip is bad. Offhand I'm not positive how you'd do that, but you might be able to see a visible result if you use a resistor of around 1K ohm to temporarily connect a chip's data pin to power or ground. On the other hand, there's a chance you might damage something that way.

[PowerPup]

Found this applefritter topic where someone posted the rom dump and some assembler files. He also shared the schematics here.

I have re-uploaded the rom dump file with the proper file extension here: http://www.mediafire.com/?84wasyd26m74y6l

Not sure if there's anything that will help, but it may end up useful somewhere along the road.

[JDW]

...you might want to monitor the 5v output with a scope, and set it to trigger on anything below 4.8v or so. By measuring with a multi-meter, you won't catch brief power supply glitches.

Good idea. That will have to wait another week though, since I would need to bring a scope home from the office and have time to do the tests. But what I can say for now is, my PSUs work perfectly when powering my main SE/30 machine, which has 128MB RAM, a DiiMO 50MHz 68030 PDS accelerator and a PDS MacCon Ethernet card.

So I cannot say yet if the PSU is the problem. All I can say is that when I install the socketed Daystar 50MHz 68030 accelerator onto the SE/30 logic board, the machine locks up after a while. If the accelerator were bad, I would expect it to not boot at all or lock up right away, but that is not the case. So I then was suspecting it could be that "socketed" accelerators perhaps require a much more stable 5.00v source. It's just a guess. But to test that theory I would need a totally different PSU that could supply 5.0v at say 10A or more continuously, so there are no voltage dips.

So this is why I am currently using the Xceed setup on a non-accelerated SE/30. Having grown accustomed to my 50MHz DiiMO, I must say that going back to 16MHz is quite painful indeed. It's also annoying because I want to see this socketed accelerator work without lockups. When the socketed accelerator does work though, it's just as fast as my 50MHz DiiMO (obviously, since both are 50MHz 030's).

If you suspect a DRAM or SRAM chip has gone bad...

In terms of main system RAM on the SE/30 logic board, there are no worries whatsoever it is bad. It is known good RAM. Indeed, I have numerous known-good SIMMs and I have tried them all. In good logic boards, they work fine. But in my socketed logic board that I recapped yet still gives me simasimac at cold boot, no RAM or ROM works. So I know something is awry with that logic board. I just don't know what. I really want to know though because it's my only other socketed logic board. And I want to resurrect it so I can try the socketed Daystar upgrade on it to see if the logic board could have anything to do with the lockups.

Now if your comment was referring to the RAM on the Xceed card, I'm not that far yet. But hopefully the information I am providing below will assist those smarter than I to direct me to the specific area to test/fix.

...draw a black or plain white background in hypercard and make lines in the exact locations and mark them. Then you could count pixels.

I've done better. I've taken screen shots on the SE/30 and at the same time I've shot photos. The screen shots don't show the dotted line, but I put both in Photoshop, resized the photo to overlap the screen shot, then I simulated the dotted line with perfect pixel precision.

My full set of photos and associated screen shots are found here:
https://docs.google.com/leaf?id=0B3mQLg ... y&hl=en_US

Measuring from the left side of the screen, we have the following data for the vertical line anomaly:

Gray Depth     Dotted Line Location
256                96th pixel from the left
16                  192nd pixel from the left
4                    383rd pixel from the left

If you doubt me, download the GIF files and examine them yourselves. I increased the size of the screen shots by 400% in Photoshop using "Nearest Neighbor" so it is a perfect 4x magnification without any fuzziness, making it easier to pick out individual pixels and count them.

The only odd thing I noticed is that the distance from the left (to the dotted line) for 16 grays is exactly twice that of 256 grays. So I thought 4 grays should be twice that of 16 grays, but I am 1 pixel short for some reason (393px instead of the expected 384px).

Also note that despite the fact I had the Monitors control panel set to grays, two of my screen shots came out in 256 colors for some reason. I was switching back and forth between CANVAS 3.5.6, and CANVAS was doing strange this to the grays in the Monitors control panel, so perhaps that contributed to 2 of the shots being in color and the other being gray. Not sure. Anyway, you'll notice that I have 2 photos labeled "256." One is labeled "smooth." You can clearly see the difference between then when looking at the bottom of the Monitors Control panel. The smooth one was created in the Finder, when I switch from another depth to 256. But the other non-smooth 256 file is showing choppy grays at the bottom of the Monitors Control Panel. This happens after I switch from the Finder to Canvas. I think Canvas is doing this, switching around the grays.

But something else to consider...

Have a close look at the photo (not the "smooth" one) and screen shot for 256 grays. Note how there is a strange set if 9 stray pixels appearing toward the right side of the screen, between "PM" and the "CC" menubar icon, running in a vertical fashion from the top to bottom of the screen. They appear to be shades of red and dark blue only. What's interesting about this is that those pixels even appear in the screen shot! So what do you make of this? Clearly, Canvas caused this because if you look at my other 256 "smooth" photo you will not see those artifacts at all (when the grays at the bottom of the Monitors Control Panel are smooth).

Lastly...

For those of you just entering this thread, please be sure to see the two videos I've made and my photos, which visually show some of the things I've been talking about in my recent posts:
http://youtu.be/7wTqLyfJtGs
http://youtu.be/mKJszJMRZM4
https://picasaweb.google.com/1033656723 ... celerator#

[bigmessowires]

OK, I think I understand now. You have three unrelated problems being discussed concurrently.

1. SE/30 logic board with all upgrades removed shows horizontal lines and won't boot (SimasiMac), even after re-capping
2. Daystar 50 MHz accelerator kind of works, but caused occasional lockups.
3. Xceed grayscale card works, but shows a vertical line whose position changes with the monitor color depth.

Does that sound right?

For 1, there are a couple of other suggested remedies for SimasiMac (other than re-capping) mentioned here: http://www.biwa.ne.jp/~shamada/fullmac/ ... #SimasiMac I know nothing about it, but maybe it helps? For all I know, you may have written that page yourself.

For 2, it could be anything really. Power supply problems is one possibility, but I'd guess it's more likely a borderline component on the Daystar card, maybe triggered by temperature.

For 3 I agree with trag's earlier statement that it's very likely a VRAM problem. The way the line moves about with color depth makes that pretty clear. His suggestion of blowing cold air on the chips sounds much better than my idea of probing with a resistor, although the end goal of identifying the faulty VRAM chip is the same. Assuming you could find the faulty chip, do you have any source for replacements?

[JDW]

Does that sound right?

100% correct.

For 1, there are a couple of other suggested remedies for SimasiMac (other than re-capping) mentioned here: http://www.biwa.ne.jp/~shamada/fullmac/ ... #SimasiMac

I have been performing SE/30 logic board recaps for several years now. And until now I have had one one other board (the standard, non-socketed type) which continued to show horizontal stripes at cold boot despite the new capacitors. And at that time, I tried the 1k-ohm pull-up resistor across UB11's pins 7 & 15, but to no avail. But I've never been able to figure out that UB11 part logically, since UB11 is a "sound" chip and as my video shows I am clearly getting sound -- indeed robust, high volume sound! So if UB11 really did not a pull-up, would it not adversely affect sound? And I don't see why that sound chip would result in horizontal lines on the screen. And lastly, since I've never had access to a Bourns filter (for RP2), I never have been able to rest that.

For 2, it could be anything really. Power supply problems is one possibility, but I'd guess it's more likely a borderline component on the Daystar card, maybe triggered by temperature.

The only way for me to test if a rock solid 5.00v power source would solve the problem is to have an ATX or similar high-output PSU directly connected to the SE/30, which I currently do not have.

The underside of the Daystar board contains only ceramic SMD caps, SMD tantalum caps, and SMD resistors -- none of which are prone to failure even after many years of constant use, nor are any of these physically marred/burned/cracked:
https://picasaweb.google.com/1033656723 ... 8640690242

Therefore, if indeed there is a problem on this board, one would logically suspect the chip-side (which is not something to troubleshoot for the faint of heart):
https://picasaweb.google.com/1033656723 ... 1352856226

For 3 I agree with trag's earlier statement that it's very likely a VRAM problem. The way the line moves about with color depth makes that pretty clear. His suggestion of blowing cold air on the chips sounds much better than my idea of probing with a resistor, although the end goal of identifying the faulty VRAM chip is the same. Assuming you could find the faulty chip, do you have any source for replacements?

Well, not having a can of that cold air, I've not yet tried it. But as you properly point out, even if I do try it and identify a chip with it, I have no chip replacements nor access to any.


So for now, I look at those 3 problems in the following order in terms of repairability (with 1 being the easiest to repair and 3 being the hardest):

1. Simasimac board
2. Daystar accelerator
3. Xceed PDS video card (vertical line problem)

This by no means even 1 is "easy," as I would have solved it by now had such been the case. Further technical thoughts would be appreciated. Thanks to all for your input.

[JDW]

With regard to my Simasimac SE/30 logic board, I have made some headway. Aided by my Apple and BOMARC schematics, I used a DMM's Continuity Check feature (beeps when both probes are shorted) to painstakingly check the board, pin by pin. I started off in the most logical manner, assuming the problem may center around the ROM. I felt that most logical in light of past experience with the ROM showing unusual artifacts on the screen. Furthermore, the capacitor that leaked the worst was SMD cap C12 (47µF). Even though I cleaned that area thoroughly more than once with high grade dehydrated Ethanol, the problem remained. So I decided to investigate using Trag's advice about thru holes.

I checked the ROM pins one-by-one, with one probe on a ROM pin and the other probe testing various legs of different chips to which that pin should lead (accordingly to my schematics). All the "Address" pins of the ROM SIMM checked out OK except one, pin 45 (A22). Pin 45 of the ROM should lead to pins 3 & 6 of UI4, as well as to the Glue Chip (IU8) and the CPU. I found A22 connecting the IU8 to the CPU, and the CPU to IU4 and IU4 back to IU8, but none of those points led back to pin 45 of the ROM (A22). I then desoldered C12 and found the problem.

Pin 45 of the ROM goes to a via, then on top of the board nearest C12 and the battery, then to another via about 1.5cm away. It's that 1.5cm long trace that is broken (on the top of the board). And it appears the break is at the top of the thru hole via, on the top of the board. Have a look at my photo:
https://picasaweb.google.com/1033656723 ... 4101043730

Note the white silked text "C12" and "D1" and "D2". Now note the "+" sign above C12, and that cap's corresponding via. Just 2mm above that is another via. That leads to pin45. Follow that via straight down to just 2mm below C2, and you can see the other via. That's the broken trace, broken at the bias. It makes logical sense too, as that is where the majority of the spilled fluid was, sitting atop those two vias for a few years I would expect. The via above the "+" in the photo is hard, but the other one is soft when I press on it with a metal pin.

I could just run a wire to attach those two points, but I am not sure if that is best. This is a multi-layered board. And unfortunately, I do not know if there are more than 3 layers. Further, I have schematics but I don't have PBC layout files which would show how many wires splice off the same via. Hence, if I've got a bad via, it's easy to fix that via by running a wire on the top and bottom of the board, but that won't help me if there are breaks to that point in different layers WITHIN the board.

Since I am not experienced fixing vias of multi-layered boards, I would appreciate your advice. (And if anyone happens to know how many layers the SE/30 board is and/or have access to PCB layout files, I would certainly appreciate getting that information from you.)

PM me if you wish to have access to my BOMARC and Apple SE/30 schematics.

I look forward to your advice. Thanks.

[trag]

And yet, when I booted I again got the sad Mac "chimes" and the horizontal lines, as shown in my new 720p video here (please take time to watch it):
http://www.youtube.com/watch?v=mKJszJMRZM4

I've watched all the videos, albeit without sound. My computers at home can't play them at all because there aren't recent enough plug-ins for those old machines and the computer at work has no speaker.

For the earlier Xceed videos, I still believe that's a VRAM chip problem. I don't see how it could be any of the circuitry (e.g. the muxes) between the VRAM and the DAC without causing a lot more than one line of bad video.

In this most recent video, are the alternating horizontal and vertical bands exactly the same height? In other words, are the dark areas the same height as the white areas?

I don't know enough to say for certain, but my two thoughts are that if the stripes are the same height, perhaps one of the two VRAM chips is malfunctioning, or perhaps you have a break in an address line (those digested vias, I mentioned).

In the former case, you can easily test by taking the VRAM chips from a working SE/30 and installing them in your problem logic board. I believe that the on-board VRAM chips are two of the socketed chips.

In the latter case, it's going to be a matter of tracing connections, but you can limit it to the address lines, which you should be able to find the start of at the CPU. The problem is that some of them probably go into the GLUE chip and then exit as non-continuous wires. But I think those address lines wouldn't be the one's we're looking for -- although, the CE_ pin or the OE_ pin on one of the on-board VRAMs might cause this problem depending on how the video is split across the two chips. So I'd trace backwards from those pins. Also:

You can also start your search a little bit intelligently, although there may be circumstances of the SE/30 design which foil this logic. If the stripes are four pixels tall, for example then I would guess that the address pin which alternates every 4 X 512 bits is the problem. So that would be address pin 10 (if the least significant pin is '0'). I might check 9 and 11 - 13 or 14 as well.

But I could be completely wrong. There are probably ways to cause this problem that I haven't imagined. Someone who did component level Mac repair back in the early 90s would have the experience you need.

Say, does "The Dead Mac Scrolls" mention this problem? Does it cover the SE/30? If not, then a look at "Mac Classic & Se: Repair and Upgrade Secrets" may be in order. If you don't have it, I can try to remember to look through it when I'm home.

Could it really be that gunk is still causing this?

It seems unlikely after the thorough cleaning you gave it. There could be that hidden nugget of conductive detritus... I'd be more inclined to believe an eaten via which doesn't display it's destruction to the eye alone.

[trag]

I could just run a wire to attach those two points, but I am not sure if that is best. This is a multi-layered board. And unfortunately, I do not know if there are more than 3 layers. Further, I have schematics but I don't have PBC layout files which would show how many wires splice off the same via. Hence, if I've got a bad via, it's easy to fix that via by running a wire on the top and bottom of the board, but that won't help me if there are breaks to that point in different layers WITHIN the board.

Ah, now I'm caught up with your latest post. I would run the bypass wire. I'm pretty sure these are four layer boards, with internal ground and power planes and signal layers on the top and bottom. More importantly, I can't imagine how running a bypass wire would do any harm, even if the board has more than four layers. At worst (I think) it just won't work.

You might also probe A22 in the PDS slot and see if it connects to either side of your broken connection. If it does connect that would seem to reduce the likelihood that there are additional broken connections inside the board.

Oh, and regarding #2, the Daystar Accelerator. I agree that there are a lot of variables, so try altering the ones which you easily can. The 68030 is socketed. Try swapping it with one from your reliable PowerCache board. Note down the date codes on the two chips first. It's surprisingly easy to get them confused in the heat of testing and not know which came from where.

Similarly for the FPUs. Those chips, at least, are easy to swap for a quick reliability check.

Finally, in my post above, it looks like I was wrong about the SE/30 on-board VRAM chips being socketed. All the chips (PALs) below them in your photo are socketed, but it looks like the VRAM is soldered down. With your discovery of a broken address line to the ROM, it's probably irrelevant, but I thought I should mention it.

[JDW]

I'm pretty sure these are four layer boards, with internal ground and power planes and signal layers on the top and bottom. More importantly, I can't imagine how running a bypass wire would do any harm, even if the board has more than four layers. At worst (I think) it just won't work.

First of all, thank you for the reply. And thanks for viewing my videos. I talk a lot in those videos, so you may wish to find a way to get the sound to work!

In my examination of several thru-hole vias last night, I noticed that some wires from connectors will route from a connector pin to a via, but then you cannot physically see any wires on the top or bottom of the board leading from that via to another place on the board. Yet, if you hold the board up to the light so you can see light shining through the back of the board, you can then see a tiny little wire inside the board leading away from that via somewhere else. And this holds true for "address" lines that are certainly not "ground or power planes." Because of that, I was thinking there is a "signal" plane (perhaps more than one) inside the board. And that's where a PCB layout diagram for the SE/30 motherboard would come in handy. If I know all the lines that lead to/from a particular via, I then don't need to worry about resurrecting the via itself, as I could run direct wires to all the points.

I agree with your last sentence that running a wire from the bad via on the top and bottom of the board would not harm anything, it may not solve the problem either. But then we don't know if the problem is not solved because there are other wires connecting to that via inside the board (which my new wires on top/bottom do not re-attach), or if there are other eaten traces. Only by truly fixing each problem can I then rule out that fixed section as possibly contributing to additional problems I find.

[bigmessowires]

Hmm, whether or not there are broken signal traces in the inner layers, can't you proceed as you have been, checking out the board with a continuity meter and comparing to the schematics? Once you add this first wire, you can confirm that the ROM pin 45 (A22) connection is working now. If that doesn't get the Mac running, then you can keep checking for more continuity problems and fix them with additional wires, verifying each fix as you go.

[JDW]

can't you proceed as you have been, checking out the board with a continuity meter and comparing to the schematics?

Of course. But that is more time consuming and error prone as a result. A PCB diagram would show me all I need to know about each and every via at a glance.

It's not a matter of sheer laziness. I really try to make the most of each free moment because I don't have that many of them.

Furthermore, I have found some minor inconsistencies between the BOMARC and Apple schematics, which lead me to believe there could be an error or two in there. I do keep notes though, so if I do find an error, it will be documented and I will perhaps even change the schematic at some point (to provide to others who ask for them).

So later this evening I will carefully examine the schematics again, then decide if the two bad bias truly can be restored simply by soldering in an external wire between them.

[trag]

In my examination of several thru-hole vias last night, I noticed that some wires from connectors will route from a connector pin to a via, but then you cannot physically see any wires on the top or bottom of the board leading from that via to another place on the board. Yet, if you hold the board up to the light so you can see light shining through the back of the board, you can then see a tiny little wire inside the board leading away from that via somewhere else.

That does sound like more than four layers. Perhaps six layers. I think the chances of a complete PCB diagram turning up is low. Unless someone made one by examining the SE/30 board. Apple certainly isn't going to have released it. Unfortunately.

You might apply a large dollop of solder flux and apply heat to the hole. That should remove the oxides in the hole. Perhaps use some desolder braid, or maybe blow the hole out while it's hot. I'm not certain of the best way to clean it out, but I'd work toward cleaning out the oxides and getting fresh solder adhered in there.

Once it's cleaned out, insert a bit of stripped wire wrap and solder in place. There's a pretty good chance that if there are additional layer connections in there, the solder and wire will make a connection to them.

[JDW]

Well, I fixed the PCB trace that had been rated by leaked fluid (in the vicinity of the battery). Unfortunately, I get the same exact response -- horizontal lines and a sad Mac chime, both exactly as they were before (and as they appear and sound in my video). So obviously, this is not the only broken trace and/or there could be a bad chip on the board.

I spent a lot of time last night checking points with the aid of my schematic. I checked all the pins on UK6 (video ROM), D0-31 (Data pins) leading from the ROM to the RAM SIMMs and to D4 - D19, I reverified that pin 45 of the ROM (Address A22) properly connected to all the points I could find on my schematics (proving my fix was good). So far, I've not found anything else bad, but there are hundreds of other places that would need to be checked, and even then one cannot know if a chip is bad. Further, I am still concerned about resurrecting vias in light of this being a multi-layered board. I could easily spend another 5-10 hours checking points and still may not come up with a remedy. I just don't have 5-10 hours or the desire to commit so much time. I will keep testing the board when I have spare time, as I am not to not sleep well at night until a problem is solved. But I must admit I am rather frustrated with this board.

Had I another socketed board, I would be content with just putting this board out of its misery. But I wanted to test the Daystar accelerator in another socketed motherboard to see if that resolved the lock-up problem I had with it. I did test the CPU of the Daystar accelerator last night. I pulled the 68030 chip from the Daystar board and put it into my known-good socketed SE/30 logic board, then I fired up the machine and ran Norton System Info (benchmark utility), followed by running extensive Norton Disk Utility tests on my 4.5GB hard drive's 3 partitions -- all of which put a good deal of stress on RAM, CPU and Disk. I left the machine on all last night (with screen brightness turned down to avoid burn-in), and the machine never locked up once. I then used it a little while this morning and it worked fine. So the CPU of the Daystar upgrade is not the reason why that upgrade is locking up. That's a fact.

[JDW]

After spending some additional hours testing and finding nothing wrong, I then came across something new. J12 is the main connector on the motherboard, which pulls power from the analog board. Within J12, pins 12 and 13 are connected together (as per my schematics) and route +5v throughout the logic board. The problem part is that when touching my DMM in Continuity Check mode between pins 12 or 13 and Ground, I get a short. So the +5v line is being shorted to ground somewhere on the board. The problem is, where?

I checked the polarity of all my replacement caps. They are facing the right way. They were all brand new caps (well, new when I bought them from Trag a few years ago), so I doubt they are bad. So now I need to find the short.

For good measure I put my DMM across pin 12 and Ground on a known-good logic board. It does not short to ground. So that proves that this short on my other board is indeed a problem short that needs to be fixed.

Interestingly, despite the +5v line being shorted to Ground, I get the horizontal lines and chimes of death at startup. I would think that with a short on the logic board, I certainly should not get any sound. Yet, the sound works fine, and is quite loud too.

Thoughts?

[trag]

Interestingly, despite the +5v line being shorted to Ground, I get the horizontal lines and chimes of death at startup. I would think that with a short on the logic board, I certainly should not get any sound. Yet, the sound works fine, and is quite loud too.

Thoughts?

It does seem like with a short that you should not be getting anything from the logic board.

Are you using a continuity meter or an ohmmeter for the testing?

If the former, try setting your DMM to ohmmeter and measure the actual resistance between the connector pins. Use the most sensitive setting which gives you a useful reading.

Do the same thing across each of the bypass capacitors. As you get closer to the short, the resistance should fall -- although that effect could be overwhelmed by simple differences in how well the probes make contact with the various test points.

I would also check across the battery holder pins. There's a lot of space under the battery holder for problems.

Do you have access to an adjustable power supply? If so, adjust it to 5V. Turn it off, connect it to the GND and 5V pins on the logic board and turn it on. How much current does it report? Try increasing the voltage a few tens of millivolts. Does the voltage increase or is too much current drawn from the supply?

Alternatively, or in addition to the above, connect the logic board outside of its frame so you have access to all of it. Power the machine up normally. Run your fingers just above the board looking for a hot sport. Touch each chip and capacitor and see if any of them are particularly warm.

Finding a short is a pain. If it was a dead short, you could try the old trick of running the voltage up until the short burns out. However, you seem to have a rather resistive short, since the machine is still getting enough voltage to kind of boot up. So the old over-voltage trick would probably fry the components on the logic board.

[JDW]

Thanks for the advice, Trag.

My Digital Multimeter (DMM) can measure Volts, Amps, Ohms, and also check diodes and continuity. When in Continuity/Diode check mode, the DMM beeps at me when both probes are touched together or when I touch each probe at the end of a single wire (i.e., when I get a short). It also gives me a number on the LCD when in Continuity check mode, which shows resistivity. It beeps at me when that number is about 20 or less.

I just tested the board with the DMM set to measure resistance (Ohms). And during my test I saw the resistance between Pins 12/13 (+5v) and Ground slowly increase to about 34.9-ohms. After it increased beyond 20-ohms, I switched back to Continuity check mode and put the probes across pins 12/13 (+5v) and Pin 1 (Ground), and the DMM would not longer beep at me (obviously, because resistance had increased so much it was no longer a dead short).

But if the resistance slowly increased, that would indicate a capacitor at the heart of this problem, would it not?

I also put my DMM probes across a 10k-ohm resistor, set the DMM to read voltage, and then I put the resistor across Pins 12/13 (+5v) and Pin 1 (Ground). I didn't see anything on the DMM screen, but when I put the DMM back into Continuity check mode and then put the probes directly across Pin 12/13 (+5v) and Pin 1 (Ground), it was back to beeping at me again (showing me signs of a short). And this test too would indicate a capacitor problem, with the 10k resistor having discharged the capacitance.

Thoughts?

[JDW]

When putting a 3A capable 5v power supply across Pin 12 (+5v) and Pin 1 (Ground), the voltage drops to 4.83v and the current is 1.51A. Checking the same power supply when no load is applied shows 5.01v on my DMM (i.e., the voltage drops from 5.01v to 4.83v when I connect the power supply to the SE/30 logic board).

I left the power supply connected and powered ON for three minutes. During that time, 5 chips got warm, all of them the PALs: UI6, UG6, UG7, UE6 & UE7. I physically touched all the chips and capacitors with my fingers. Not even the CPU got warm. Only those 5 socketed PAL chips. I would classify it has "hot" but not so burning hot I could not keep my fingers on the PALs.

After removing power and waiting about 3 minutes, I put my DMM in Continuity Check mode across Pin 12 (+5v) and Pin 1 (Ground). This time it did not beep at me. I then switched to check resistance on my DMM and measured 43.9-ohms across those same pins. But while keeping my eye on the DMM's LCD, I could see the resistance value slowing going down. I then removed all 5 PALs from their sockets, checking the resistance as I pulled each one. The resistance continued to drop at the same pace, unaffected by my removal of the PALs.

Each of the PALs were correctly socketed. I know this based on the Apple part numbers on the chips in comparison to what is written on my schematics. I also know how they were installed the first time I looked at the board, before I ever pulled the chips to clean the board.

After all this, I reconnected my power supply again, this time using 4 alligator-clip jumper wires instead the 2 that I used before. I was thinking that two wires alone may be limiting the current a bit. So I connected Pins 1 and 4 (both board Ground) to my PSU Ground, and I connected Pins 12 and 13 (both board +5v) to my PSU's Positive line, then put my DMM on to check voltage. This time I read 4.90v at 1.56A. I then slowly increased the voltage on my PSU. I saw a proportional increase in voltage on my DMM and the current increased too. And as before, the PALs got warm, but nothing else.

I would appreciate hearing your thoughts in light of this.

Thank you.

[trag]

PALs get hot. I was surprised by this when I learned it. I was fiddling with a GAL from an Outbound Floppy Controller board and thought something was wrong with it because it got so hot. But back in the circuit it worked fine. And info requested on sci.electronics.repair resulted in folks saying that PALs get hot.

So, I suspect that warm/hot PALs is not a problem.

Which doesn't help with finding your short problem.

Capacitors in a circuit, especially bypass capacitors, will look like a short until the capacitors charge. That's because the caps are a place for current to flow into while the caps are charging. A DMM does not supply much current, so it takes a noticeable amount of time for them to charge. So I do not think that your slowly increasing resistance is a suggestion of a capacitor problem. Doesn't mean it isn't, though.

One of the results you had where the resistance was still about 35 ohms when you checked it again, probably just means that the caps charged up during the first measurement and hadn't discharged before the second test.

The question is, is ~35 - 40 ohms the proper resistance for your board with all the current paths on it?

At this point, I would get out a working SE/30 board, preferably also one you have recapped. And take the same measurements on it as you have taken on this one. In other words, is its static resistance about 40 ohms from 5V to GND. Does it draw about 1.5 amps when supplied with 5V. Etc.

[JDW]

Trag, thanks for the info and advice.

I tested my known-good socketed motherboard, using the same known-good RAM SIMMs as I used on the bad board. My known-good board was also recapped in exactly the same way and with exactly the same replacement caps (your kit of SMD tantalums and axials). I used two alligator-clip jumper wires on this board as I did in my final test on the bad board. I tested my power supply with a DMM before I connected it, and it measured 5.00v. When I connected the 4 jumpers and then switched the power supply on again (on my known-good board), I measured: 4.88v @ 1.41A. That reading is a tad lower than the reading I got on my bad board, but it is not substantial difference. The two motherboards are different revisions though, with the location of C12 being a little different, so perhaps that also contributes to the slight difference in voltage and current.

I also noted this time that, in addition to the PALs, the following components also got noticeably warm to the touch:

Y2 (OSC)
UH7
UG12

They might have also gotten warm on my bad board too -- I don't remember.

I also tested the resistance between Pin12 (+5v) and Pin1 (Ground) very quickly after I turned off my power supply. For a brief instant I measured 100-ohms. But I could see on the DMM's LCD that the resistance dropped rather quickly down after that. It took only a few seconds to go down to 63-ohms. I then removed all the jumpers and my DMM, and began typing this post for a few minutes. Then when I tested resistance again, it was down to about 28-ohms and dropping.

Before I did any of these tests on my known-good board, I put my DMM in Continuity Check mode and put the probes between Pin12 (+5v) and board Ground. It immediately beeped at me, indicating a dead short, just as it did with my bad board. So this confirms that the bypass caps show a dead short to my DMM when it is set to Continuity mode (when the caps are fully discharged).

My next test will be to remove the PALs from the known-good board and put them in the bad board to see if that resolves the problem. Hopefully, the problem with my bad board is not so such that it will fry my known-good PAL chips. If that test fails, I will then put the PALs back in the good board and test it to confirm the PALs are still good. I will then continue the painful process of checking every via and every pin, in accordance to my schematics. But I must say this is not an enjoyable process in light of the time it takes.

[bigmessowires]

I reviewed this thread from the beginning, and was reminded that it actually makes the startup sound "bong" when powered on. That means it's actually running and getting at least part-way into the boot sequence code in ROM. Have you tried actually booting the machine, inserting a floppy? If it is purely a video problem, then maybe the computer itself is working fine. I'm not sure what that would prove, but might help narrow down the problem.

[JDW]

it actually makes the startup sound "bong" when powered on.

No it doesn't make a "bong." As a part of my video, you can clearly hear that it only makes the "chimes of death" which are always a part of a Sad Mac Error Code screen. And of course you unfortunately cannot see that Sad Mac Error Code due to those horizontal lines:

http://www.youtube.com/watch?v=mKJszJMRZM4

Because it is a Sad Mac error/fault, it will not boot. No Macs boot when the Sad Mac "chimes of death" sound. The problem that causes those chimes must be fixed first. And that is what all my recent posts have been about. Trying to find that elusive logic board fault!

[bigmessowires]

Ah sorry, I re-read it too fast and misinterpreted the startup sound.

[bigmessowires]

BTW, there's an SE/30 motherboard up on eBay for $1. I'm not sure what the socketed type looks like... is this one? http://www.ebay.com/itm/Vintage-Apple-M ... 1c1ea89f33