Cyanopsis wrote on 2024-10-23, 09:53:

Yes, that's exactly how I'm interpreting this trace. However, there's no connection on the first path to R72. It is and it looks cut. If you don't oppose to the idea, I am going to solder and fix this connection.

I'm sorry, I couldn't notice the broken trace from "via 4" to resistor R72 on the picture. It seems like this broken trace is the culprit for the problem with storing the BIOS settings. Do this fix and test the motherboard 👍🏻

P.S. After second look at the picture, now I see the broken trace. Check the nearby trace (from R49) as well, even if it seems Ok on the picture.

Fingers crossed! This is a tiny tiny trace but a small blob of solder should to it.

Out of respect, I just want to inform you that I haven't had the time to do much with this, but will continue this weekend. I did remove the three JCC pins to be able to work a little better and I have also been able to track JCC pin 2 towards south bridge. The last spot that I'm able to trace is a via beneath the actual VT82C586B chip, in the center almost. Still no reading on the VBAT pin when I check for continuity however. I will solder and close the JCC pin 3 first anyway.

I took some time late last night to fix the trace from VIA 4 to R72 and while the trace is super duper tiny, I think I did a decent job repairing it with a wire. On the picture, it looks like it's connected to JCC pin 3, but the VIA is just beside the black plastic holding the pin.

However, sadly, I don't think I have fixed it. 🙁
Works: The computer is now keeping date and time, even after I unplug it from power.
Doesn't work: BIOS settings resets for every reboot (not just when i cut it from power). I get both "CMOS checksum error" and "CMOS battery failed" at POST.

Measuring the trace from the battery, I get 3.3V to the point of VIA 4. Right after R72, I get something like 2.4V. That includes JCC pin 3 and all the way to the VIA beneath the south bridge after i set the jumper on JCC 2-3.

Of course, that's what a resistor does and the trace is also connected to D6 and C25 (whats a C?) in this trace. The thing is, when soldering I had to redo the solder joint to R72 a few times and doing continuity tests on this resistor gave me different results for each time. I don't know what kind of voltage South bridge is expecting and how to calculate the ins and outs of this loop but I'm worried the tiny R72 is broken somehow. Are they able to withstand that kind of heat a few times over?

Not sure how far I'm able to take this really. If South bridge is expecting something very close to 3V and I'm not providing it, then maybe I'll redo the whole thing and replace the (failing?) resistor. Otherwise, I'm not sure.

measure its resistance, should be 1K

rasz_pl: Would I be able to do that on the PCB or do I have to desolder it?

This is how it's all connected by the way.

VIA 4: from battery +
VIA 5: To D6 on both ends.
VIA 6: To South bridge

The letter "C" marks capacitor.

Are you sure that "via 5" is connected to both ends of diode D6 (such connection shorts D6 and makes it redundant)?

What if R72 resistor is not factory original? 1 kOhm seems too much for this 3 V battery circuit, 100 Ohms (or even 10 Ohms) seems more appropriate value to me. 2.4 V for CMOS seems too low. Unfortunately on TRW the value of R72 can not be seen on the motherboard's pictures.

I'm fairly certain that VIA 5 is connected this way, but will of course double check.

The "102" on the resistor doesn't say anything about resistance?

Cyanopsis wrote on 2024-10-25, 13:48:

The "102" on the resistor doesn't say anything about resistance?

"102" is a combination of "10" and "2" which means to take "10" and multiply by 10^"2". So it should be 1 KOhm.

I just did a little test on the side with an old school 1k resistor and 3.3v - resistor - diode gives me 3.0v so I could probably try to create a new circuit with this resistor and try it with a temporary solution. Diodes has no resistance right? The 2.5v that I'm getting shouldn't be because of the d6 mystery, right?

Cyanopsis wrote on 2024-10-25, 16:31:

I just did a little test on the side with an old school 1k resistor and 3.3v - resistor - diode gives me 3.0v so I could probably try to create a new circuit with this resistor and try it with a temporary solution. Diodes has no resistance right? The 2.5v that I'm getting shouldn't be because of the d6 mystery, right?

Actually diodes do have some resistance even in "open" direction (forward bias - positive anode, negative/grounded cathode), which causes some voltage drop.

Check with the multimeter in resistance test mode if R72 value is 1000 Ohms (1 kOhm).

Cyanopsis wrote on 2024-10-25, 10:24:

rasz_pl: Would I be able to do that on the PCB or do I have to desolder it?

You can measure resistance in circuit, with motherboard powered off and battery removed.

Cyanopsis wrote on 2024-10-25, 10:24:

VIA 4: from battery +
VIA 6: To South bridge

correct

Cyanopsis wrote on 2024-10-25, 10:24:

VIA 5: To D6 on both ends.

remember how I told you to measure diodes and you said D6 was only passing one way, connection here would mean shorted Diode

analog_programmer wrote on 2024-10-25, 11:02:

What if R72 resistor is not factory original? 1 kOhm seems too much for this 3 V battery circuit

1K is standard on all board schematics I have access to, example

rasz_pl wrote on 2024-10-26, 00:47:

1K is standard on all board schematics I have access to, example

The attachment batt.jpg is no longer available

Ok, if resistor R72 is factory original and it's measured value is 1 kOhm, then this 2.4 V on SB leg 102 (RTC Battery. Battery input for internal RTC) should suffice and there should be no problem with storing the bios settings. However there is a problem.

At least now real time clock seems to work.

VIA 6 to ground resistance might be too low excessively dropping voltage (for example slightly cracked C25 or some liquid spill conducting between pads). Cyanopsis can you measure that? again with powered off system and battery removed.

Folks, I think I'm soon throwing in the towel on this one. I made a separate battery pack with a spare holder and a 1k resistor and a diode to bypass this area if I f'd up and go straight to JCC pin 2 and ground. With that, I got 3.0V on VIA 6. No difference - CMOS error and battery error.

The thing is this: No matter what, there's still no voltage on VBAT pin 102. There's no continuity between VIA 6 and pin 102. Via 6 is directly connected to VIA 7 (pictured) and it's right below the south bridge, hidden in the middle of it. I don't know where VIA 7 is supposed to go because I can't find any trace of it. Using the continuity setting on VIA 6 or 7 (depending on if I'm testing the front och back side of the board) I cant find anything around the south bridge that gives me a signal.

What do get, however, is a ground signal on pin 102 (no beep, but measurements in the hundereds). Strange? See closeup of the south bridge area. CMOS resets for every reboot (besides clock). Could there be a short somewhere?

I won't be asking much more of your time. You have helped me more than I could ask for and I will probably be looking for another board. If anyone living within the EU and has a spare jumperless mATX board with ISA, PCI and AGP (yes, it had much potential being small!), I might be interested.

Again, Thank you!!

Cyanopsis wrote on 2024-10-26, 11:33:

The thing is this: No matter what, there's still no voltage on VBAT pin 102. There's no continuity between VIA 6 and pin 102. Via 6 is directly connected to VIA 7 (pictured) and it's right below the south bridge, hidden in the middle of it. I don't know where VIA 7 is supposed to go because I can't find any trace of it. Using the continuity setting on VIA 6 or 7 (depending on if I'm testing the front och back side of the board) I cant find anything around the south bridge that gives me a signal.

It's weird that now the SB chip keeps RTC set and running without any power from PSU, but still you can't measure some voltage on leg 102 coming from the battery. From my experience with RTC modules (some Dallas variants and ODIN) the real time clock runs fine with lower voltage, than the voltage needed for keeping saved BIOS settings.

Cyanopsis wrote on 2024-10-26, 11:33:

What do get, however, is a ground signal on pin 102 (no beep, but measurements in the hundereds). Strange? See closeup of the south bridge area. CMOS resets for every reboot (besides clock). Could there be a short somewhere?

Yeah, there could be some short on the traces.

Don't give up yet. Use some magnifying glass to inspect "back" side of the mobo for some broken or shorted traces.

Cyanopsis wrote on 2024-10-26, 11:33:

The thing is this: No matter what, there's still no voltage on VBAT pin 102.

just to be sure, you are checking this pin:

Cyanopsis wrote on 2024-10-26, 11:33:

Using the continuity setting on VIA 6 or 7 (depending on if I'm testing the front och back side of the board) I cant find anything around the south bridge that gives me a signal.

With no connection at all clock wouldnt keep time. Now the thing is clock can keep time even with voltage so low VT82C586B "VBAT voltage OK" check fails.
Continuity mode doesnt have to beep, does it give you a reading?

- diode test is directional, try measuring with reversed leads
- dont check to via 6, check to the CMOC RESET header pin 2, you might have bad oxidized jumper
- one last thing to try is soldering wire directly between point 4 or 5 or CMOS header pin 3 and VT82C586B pin 102

Cyanopsis wrote on 2024-10-26, 11:33:

What do get, however, is a ground signal on pin 102 (no beep, but measurements in the hundereds). Strange?

probably normal, its an active cmos component

Cyanopsis wrote on 2024-10-26, 11:33:

I will probably be looking for another board. If anyone living within the EU

If you happen to reside in Poland I would happily take this board off your hands at scrap value ;-P

Try flashing this BIOS that has a CMOS check disabled - it doesn't increment the checksum if the voltage is low.

rasz_pl wrote on 2024-10-26, 13:53:

just to be sure, you are checking this pin:

The attachment pin.jpg is no longer available

Yes, that's the one.

rasz_pl wrote on 2024-10-26, 13:53:

Continuity mode doesnt have to beep, does it give you a reading?

On pin 102? No.

rasz_pl wrote on 2024-10-26, 13:53:

- diode test is directional, try measuring with reversed leads
- dont check to via 6, check to the CMOC RESET header pin 2, you might have bad oxidized jumper
- one last thing to try is soldering wire directly between point 4 or 5 or CMOS header pin 3 and VT82C586B pin 102

Point 1 and 2 are cleared. About the last point - seems risky. And the pin is incredibly small. If I didn't have anything left to save, then maybe, but keep reading!

rasz_pl wrote on 2024-10-26, 13:53:

probably normal, its an active cmos component

Interesting!

rasz_pl wrote on 2024-10-26, 13:53:

If you happen to reside in Poland I would happily take this board off your hands at scrap value ;-P

I'm not totally opposed to the idea of giving it away for shipping costs (from Sweden). However, keep reading!

kmeaw wrote on 2024-10-26, 15:42:

Try flashing this BIOS that has a CMOS check disabled - it doesn't increment the checksum if the voltage is low.

So there's been a kind of resurrection! 😀
Before I flashed your version I first downgraded to 1.3 and sure enough, I was able to get BIOS settings to stick as long as computer was mains powered, basically reverting to the state I was in after I got the new EEPROM and flashed the correct firmware. But my 40gb HDD wasn't detected on 1.3 (not 2.0 either) so I immedeately flashed 3.0 and started troubleshooting the CMOS error. So 3.0 works differently than the previous ones regarding checksums? And you modded 3.0 so that the checksums worked as previous versions? Clever!

So what I do have right now is acceptable in that BIOS settings are stored as long as I don't pull the plug. It's not what I want in the long run, so I will be on a lookout for a similar board, but they are pretty rare, based on my criteria. So rasz_pl, if/when there's a board that comes my way I'll be messaging you.

Thanks again!