twolazy
Veteran Member
Oh wow that RTC is dying! Think you found the problem. Guess its possible the connection could be bad, but you said you already cleaned the socket. So I'll lean towards dying RTC chip.
Last edited:
- VCF South West - June 14 - 16, Davidson-Gundy Alumni Center at University of Texas at Dallas
- VCF West - Aug 2 - 3, Computer History Museum, Mountain View, CA
- VCF Midwest - Sept 7 - 8 2024, Schaumburg, IL
- VCF SoCal - Mid February 2025, Location TBD, Southern CA
- VCF East - April 2025, Infoage Museum, Wall NJ
-
Please review our updated Terms and Rules here
Help! Micronics/Gateway 2000 486 Motherboard Mysteriously Dies
- Thread starter gatewayrepairs1985
- Start date
twolazy
Veteran Member
Here is the Dell board I have, for reference...
GiGaBiTe
Veteran Member
I wouldn't condemn the RTC chip outright, it could always be something else.
I've seen crystals going bad cause erratic RTC behavior. If the crystal isn't producing a clean clock signal, the RTC and the system in general won't work properly. It could also be things around the crystal causing problems. Bad 74xx logic, drifting/open resistors, bad diodes, etc.
twolazy
Veteran Member
Very true, but my money is on the RTC being bad, as I had the one on my board replaced under warranty mid 90s...
gatewayrepairs1985
Experienced Member
Hi @twolazy,
Wow, thanks for the information! However, I already tried replacing that RTC chip and the same symptoms still occur. I just tried it again (with a known good 6818 chip) and the same symptoms still occur.
Do you have any other ideas on what it could be?
Again, I really appreciate all the help! Let me know!
Last edited:
gatewayrepairs1985
Experienced Member
Hey @GiGaBiTe,
Thanks for the advice! Do you know how I could go about checking the crystal on this board? It would make sense that it’s the culprit, sense I can’t reset the board and the CMOS setup is acting weird. I would love the help!
Appreciate the reply!
Last edited:
gatewayrepairs1985
Experienced Member
GiGaBiTe
Veteran Member
You need an oscilloscope or logic analyzer that is fast enough to capture the clock of the crystal. If you don't want to buy one, you can try to just change the crystal under the IDE connector. It should be (but is not always) 32.768 kHz. It should be written on the body of the crystal. Make sure the components around the crystal are also good.
And…
Now this happens.
Really close to giving up here… but I don’t have another board to replace it with. So I must keep trying.
EDIT: This doesn’t happen anymore. Strange. I’m back to square one. I can’t save CMOS settings or restart the board with the reset button. Still in need of help!
Looks like the BIOS is crashing. I would suspect either the BIOS image is corrupt, or you have bad RAM. Something is causing stack smashing and sending the CPU off into lala land.
gatewayrepairs1985
Experienced Member
Thanks for the advice. I will see if replacing the crystal does anything to help. Just to clarify - this pictured is the crystal, right?
Attachments
twolazy
Veteran Member
I have a feeling these boards and saving the bios to the flash chip and not the RTC. I will test this theory tomorrow or maybe this evening.
Hugo Holden
Veteran Member
The fact that sometimes it works and others doesn't, probably means that there is a connection which is intermittently open or intermittently shorted or conduction between two or more circuit tracks. It may well be the delayed effect of battery electrolyte. If that has happened it is better to run warm de-ionized water over the affected area for at least an hour at least, contact cleaner won't work, vinegar will make it worse. Contact cleaner will not dissolve it well enough. You can use tap water in a low flow stream at the sink to run over the area, but ideally you would then wash with de-ionized water after that, then some contact cleaner and only very gently air dry with a hair dryer, held a good distance away so it only would just warm your hand at that distance. Putting pcb's in the oven is a very bad idea unless it is well controlled oven and the max temp is very low. Don't attempt to wash the board in a dish washer either.
However, there could be another reason entirely for this fault and I think it is highly likely:
I noticed that at least 3 IC's are very fine lead pitch types. Even on boards that were manufactured with Leaded solder, I have seen whiskers causing shorts between adjacent pins that are intermittent. This is because the lead wires of the IC's were Tin plated, and you get whiskers there. For that you need a small brush with bristles that easily fit between the pins. Saturate the area with CRC's CO contact cleaner and brush between the pins. If that sort of scrub causes a greyish colored slurry to appear when the washings fall into a white sink where you can see them, then there are/were micro whiskers there. Then re-try the board.
I agree with checking the clock, sometimes crystals lose their activity and the clock won't start at power up, often crystal modules can do this. That type of crystal there on your board is "probably" ok.
However, there could be another reason entirely for this fault and I think it is highly likely:
I noticed that at least 3 IC's are very fine lead pitch types. Even on boards that were manufactured with Leaded solder, I have seen whiskers causing shorts between adjacent pins that are intermittent. This is because the lead wires of the IC's were Tin plated, and you get whiskers there. For that you need a small brush with bristles that easily fit between the pins. Saturate the area with CRC's CO contact cleaner and brush between the pins. If that sort of scrub causes a greyish colored slurry to appear when the washings fall into a white sink where you can see them, then there are/were micro whiskers there. Then re-try the board.
I agree with checking the clock, sometimes crystals lose their activity and the clock won't start at power up, often crystal modules can do this. That type of crystal there on your board is "probably" ok.
Last edited:
twolazy
Veteran Member
Good point about the tin whiskers, never even thought about that!
gatewayrepairs1985
Experienced Member
Wow, thanks so much for the great reply! I will try both of these things over the next couple days and report back. I want to try the CRC CO contact cleaner first. Which IC’s did you notice that might be the culprit? Should I just try and clean all the socketed ones?
Again, thanks so much!
Hugo Holden
Veteran Member
They can explain intermittent behavior.
One classic case I had with the large fine pitch pin IC's was in an LG VDU. It started acting like a Ghost was pushing the menu button. I disconnected the button from the board and it still did it. Also there was an unusual change in screen contrast split down the vertical meridian. Luckily the penny dropped when I realized that two completely separate (or should be) parts of the circuit where becoming linked in some way. It was fine whiskers between the pins on the main processor IC.
In another case, a single whisker required the removal of the main board from one of my Tek 2456B scopes, here is the story about that one:
www.worldphaco.com/uploads/TEKTRONIX_2465B_OSCILLOSCOPE_MAIN_BOARD_INTER-TRACK_LEAKAGE..pdf
So whenever I see IC's with fine pitched pins, it always raises this question, especially on an aged pcb, if that could be the cause of intermittent behavior. It might not be, but it is worth checking.
Hugo Holden
Veteran Member
gatewayrepairs1985
Experienced Member
Thanks for the picture. I will order some contact cleaner and see what happens. Fingers crossed this is the problem. I really appreciate the help!
Hugo Holden
Veteran Member
Don't forget to select a suitable brush, Art & Craft stores have various types ideally not too soft and with bristles that can pass between the pins. In some cases I have run a thin paper strip between pairs of pins just to make 100% certain. The whiskers, if there, can be very difficult to see without high magnification.
twolazy
Veteran Member
Dollar tree sells some decent brush sets, with steel/brass/nylon bristles. The stiff nylon one be perfect.
Hugo Holden
Veteran Member
Yes, I never mentioned anything about metal bristles. Don't use ones with metal bristles,ever, they break off, fall into the gaps between the pins and short things out. Horse hair or synthetic/Nylon only.
Hugo Holden
Veteran Member
...also don't forget this remark I made about doing it; "Saturate the area with CRC's CO contact cleaner and brush between the pins".
It is not a good idea to brush dry IC pins. When it is saturated with the cleaner it prevents and electrostatic charges building up. Though it is much more risky to dry brush IC pins out of circuit than in/on a circuit board, because normally, in circuit, there are no floating input pins.
It is not a good idea to brush dry IC pins. When it is saturated with the cleaner it prevents and electrostatic charges building up. Though it is much more risky to dry brush IC pins out of circuit than in/on a circuit board, because normally, in circuit, there are no floating input pins.