Technical data

2-28 Diagnostic Procedures
Note: If the 5.0V brick has failed, it will still show approximately 2.5V, owing to the 3.3V
brick pulling up through the ASICs.
2.5.1.2 Power Levels OK but the Processor LEDs Are All Off
1. There is a power or ground short.
2. The LED controller PAL has failed.
3. One or more of the R4KIO PALs has failed. Check the PALs on the failing slices. The
PALs are at locations I5H1, J1M0, I3J9, and F2E1 for slices 0 through 3, respectively.
2.5.1.3 Power Levels OK but Processor LEDs Are All Lit
The processors are not booting from their EAROMs and PROMs.
1. Check for missing clocks.
2. Check for bad PROMs or PALs.
3. Check for a dead processor.
2.5.1.4 All Processor Slices Have Failed
The clocks may not be running. Check the clocks as follows:
1. Look for a 50-MHz ECL-level clock at pin F8.
2. Check the MC100E11 backplane clock driver at G0C8.
3. Check that the MC100E11 power supply is at 4.5V.
4. Look for a 50 or 75-MHz TTL-level clock at pin V4.
5. If no clock is present, check the local crystal at G9K7 or H5K7.
6. Check the driver at G9J8. Clock pulses should be present at pins 12, 14, 16 and 18.
2.5.1.5 A Single Processor Slice Has Failed
1. Look for a clock at pin V4 of the failing slice’s CC chip.
2. If no clock is present, check the R4k Reset PAL. The PALs are located at F9G5, G1K7,
I3J9, and I7G5 for processor slices 0 through 3, respectively.
Note: If the clock is running at 25 percent frequency, the EAROM is probably faulty.
3. Check that the processor is securely seated in the socket. Remove the heat sink and
check for snugness.
2.5.1.6 Clocks Are Good but the Processor LEDs Are All Lit
1. Check the R4kIO PAL, EAROM, and processor, as noted previously.
2. Replace the EPROM and check the board again.
3. Check the frequency of the ModeClk at N19. The frequency should be approximately
200 kHz. If no ModeClk signal is present, the processor has failed.