Hi all - I have a NeXTstation mono board (non-turbo) that powers on by itself. If I power it off, it immediately powers back on. Additionally, the red LED by the SCSI header constantly blinks. Related? Everything else seems to work OK. Any ideas? Thanks!
The scsi light is normal on the boards that have them. It was later removed. Try leaving the battery out overnight. I've seen claims that reversing the battery can solve these issues but I don't recommend it. Assuming the caps have already been replaced this is usually a problem with the RTC chip. They are common and cheap, but does require surface mount soldering.
Quote from: barcher174 on June 17, 2020, 10:51:03 PMThe scsi light is normal on the boards that have them. It was later removed. Try leaving the battery out overnight. I've seen claims that reversing the battery can solve these issues but I don't recommend it. Assuming the caps have already been replaced this is usually a problem with the RTC chip. They are common and cheap, but does require surface mount soldering.
Hrmmm, OK. I've taken the battery out and will leave it overnight. I recapped it today and used tantalums for the SMDs with the same ratings, and replaced the radials with new caps too. That did not fix it either. There was a little crud from the old radial caps (and not the SMDs, go figure) that I cleaned up with IPA. I'll double-check the RTC chip and see if the legs are corroded from electrolytic goo. Thanks!
On further inspection the RTC IC and the IC just to the right looked iffy. I removed them both and the some of the pads just disintegrated. Rather than cleaning the chips and resoldering them, I'll order some new ones and try to repair the pads and get the chips back on. Wish me luck! :)
This part of the circuit is pretty simple. I suspect it will work with the new chips. The rtc is probably the most often chip I've replaced over the years.
Well dang, I replaced the RTC and now the computer will only turn on while the POWER ON button on the keyboard is depressed. Once I let up, it turns off.
I should note that the pads were crusty under the RTC. I toned all of them except for pin 1 and 2. The pad for pin 1 (CLKOUT) was destroyed :( and I don't know where it's suppose to go. For pin 2, the pad is there, but I don't see a trace of where it goes. Schematics would be super helpful on this, but I can't find them. This board is a revision PN-1703.AD. Anyone know of schematics or where pin 1 and 2 of the RTC should go?
Thanks!
Check the diodes nearby. There are no schematics for this board. I will try to get some measurements for you.
Pins 1 and 2 appear unconnected to me. If you don't have it already the datasheet is here:
http://asterontech.com/Asterontech/NeXT_Black_Hardware_Datasheets.html
Cool, thanks -- then I must have scorched something else when removing/soldering the RTC. Ergh.
Alright, well I'm gonna move on from this board. My head is too bruised from banging it against a wall.
Anyone want a problem nextstation mono board? I'll offer it up for free + shipping (medium flat rate in the US).
I'll post this in marketplace too. thanks!
I'll take it! I have another problem board (with a different problem) I'm looking to resurrect!