I got my ZD-985 Wednesday, but I didn't get a chance to play with it until today. In preparation for the big RTC replacement, I practiced removing components on an old, and zapped by lightning, ISDN terminal adapter. I guess this could be considered my retro activity for the day.
As you can see, it works like a champ. I found that 350C is a good temperature for this unit. But I have no idea how accurate the sensor is.


Here's the patient ready for operation. The Kapton tape is there in case there are any mishaps.

The RTC is removed. It was actually harder than expected. What I should have done, and recommend you do, is add new solder to every joint before using the desoldering gun. I had to redo five joints this way. Other than that, there were no problems and no damaged traces or pads.

The socket is installed and soldered. This is a multi-layer board and there are pads on both sides, so I applied non-corrosive flux on both sides. Soldering took
two minutes at most.



I powered it up after installing a "new" RTC and I got a dead CMOS battery message! Luckily I had four others to try and the next one worked fine. I'll order some new DS12887+s from either Maxim or online store to replace these from China. To be honest, I think these are counterfeit. The silkscreening doesn't look right.


That's not the end of this thread. There is still a lot more work to be done to this P90. I have to decide whether or not to put a network card, USB 2.0 card, or SATA adapter. And which ones? 3c905B, NEC USB 2.0 card, and some generic SATA controller that has a BIOS perhaps.