Recapped IIci intermittent clock counting

[KI5NYZ]

IIci had very little corrosion and it was isolated to pin 7 of UE13. Cleaned the board and recapped with tantalums from DigiKey. Seller shipped with PRAM battery removed and there is no damage or evidence of the battery having exploded.

The clock was originally working, but now it just stays on the last set time, whether manual or NTP. Snooper says the RTC is working fine, and the set date/time is retained after power cycle or reboot. Using a fresh cr2032 in a MacBatt module.

The mac boots and runs fine. Soft poweron and shutdown/power off works fine. Have disabled all extensions except 'date & time, and alternately with just superclock enabled with no resolution. Google-fu says Y5 or the RTC may be the culprit.

Not able to measure Y5 for a few days. Is there anything else to check for?

 

[Boctor]

AFAIK, whichever crystal is the 32,768hz one, in proximity of the RTC, is its clock source. If it's anything like the SE/30 and IIcx (I think the logic is almost identical but the pinout differs?) then the 1hz source, an interrupt, starts from a leg of that 8-pin RTC. It is completely possible to have it retain PRAM/time but not tick, if something is short/broken on those lines.

When the clock won't tick, does your cursor flicker at unexpected times out of sync with normal vertical blanking, even on an idle desktop? (Not counting applications that damage/repaint constantly and always have to do this, e.g. QuickTime MoviePlayer.)

 

[KI5NYZ]

No it does not flicker or do anything unexpected. Have the logic board on the bench now and will start tracing things out.

 

[KI5NYZ]

Oscillator
Y5 - C131 & C129 good ground (16MOhm on other side)

Clock Path (as far as I can trace without understanding how the 1Hz comes out of the UE9 RBV)
UK14 p2 -> UD11 p43 good
UD11 p23 -> UE9 p103 good
R40 = 1kOhm
R40 -> +5v good (measured UD11 p23 -> F1)

+V to RTC
UK14 p20 -> D7 p3 good
UK14 p20 -> D8 p3 good
D7 p1 -> +5v good
D8 p1 -> +VBatt good
C137 p1 -> Gnd good
C137 p2 -> UK14 p20 good

Diode measurements
D7 p3 -> F1 (forward):
4.27kOhm
0.457v
D7 p3 -> F1 (reverse)
4.27kOhm (think this diode is bad)
0.9v (think this diode is bad)

D8 p3 - +VBatt (forward):
5.37MOhm
0.533v
D8 p3 -> +Vbatt (reverse):
OL (all the Ohms)
OL (none of the volts)

Please let me know if this is good enough. I think D7 is bad/internally somewhat shorted. Also, is there anything else to check on the 1pps signal past what I have done (with details please)?

EDIT: Can't seem to find a 1n914 SOT23-3 5DX (marking on diode) datasheet to finger out an alternative

 

[Boctor]

I took a second look at my IIci, as I've never had to touch the RTC in it yet. It's not only a different pinout from the previous-gen 8-pin one, but a different package entirely. I might have to probe mine now for better reference, since I was looking at a IIcx where the clock circuit had broken, and obviously that won't be as helpful to you.

Have you ever run Apple Personal Diagnostics on this IIci? When the clock isn't ticking properly, I know for sure that the Logic Board Components test in that times out.

 

[KI5NYZ]

I ran it previously without regard for if the clock was working or not. Ran it again this morning since adding an Asante, and it locked up (any other work does not lock it up, and only one attempt was made before rebooting and running benchmarks with Snooper and MacBench, which completed successfully).

Will button it back up, this time without the MacBatt since if D7 is indeed shorted I'm putting ~3v from the battery on the +5v rail. Will try APD again then.