HP Portable PLUS - Page 90

8-24 Troubleshooting
Portable PLUS Computer
Table 8-7_ Repairing the Processors (Continued,
Step
1. PWON* (test point A2E2): When reset but-
ton A2S1 is pressed, A2U17, pin 1 (PPU)
goes to OV, and the computer should go to
sleep (VccS goes to
OV, and VccDS goes to
3.2SV). As A2S1 is released,
PWON*
should rise to VccDS (3 .2SV) in 700-800 ~s .
2. A2U17, pin 8 (PPU) should pulse low for
approximately 176
~s every 128 ms . (The
PPU inputs POWER*, HIGH CURRENT*,
CARDSIN*,
lOW BATTERY, and SHUT-
DOWN are valid only while pin 8 is low.
Refer to section 5.12 for reference.)
3. SlEEP* (PPU A2U17 pin 11) is OV at turn-
on, then goes to SV.
4. DSlEEP* (PPU A2U17 pin 10) pulses to
OV at turn-on, then goes to SV. (DSlEEP*
stays at VccDS (3.2SV) when the computer
is asleep.)
5. A2U17, pin 6 (PPU) should alternately
pulse low for 82
~s, then high for 20 ~s
while the computer is awake. (This line
stays low occasionally
when the PPU is pro-
cessing a command.)
6. Check the 80C86 CPU RESET line (A2U1,
pin 21) for a SV pulse as the computer
wakes up; this line should then stay at OV.
7. Check the LCD controller elK line (A2UlO,
pin 36) for S-MHz signal, 50% duty cycle.
8. Check HP-Il interface TSClK* line
(A2U1S,
pin 22) for 2-MHz signal, 50%
duty cycle.
9. Check wait state counter line 2A (A2U2, pin
13) for 16-MHz signal,
50% duty cycle.
10. Check the MClK lines on the
muIticontroIIers (A2U16 and V18, pins 23)
for 2.667-
MHz signal, 50% duty cycle.
11. SLEEP (A2U17, pin 34): pulses to 3.2SV at
turn-on,
then OV.
12. The clock signal (A2U19, pin 8): S.33-Mhz
signal, 33%
duty cycle.
I
Response
If bad, try replacing A2S1, A2CS, and A2R27 on
the motherboard PCA. If still bad, replace the
PPU (A2U17).
If not, replace A2Ul.
If bad, replace the PPU (A2U17).
If bad, replace the PPU (A2U17).
If bad, replace the PPU (A2U17).
If bad, replace A2U23.
If bad, replace A2U23.
If bad, either clock controller A2U6 or the 16-
MHz crystal
A2Y1 is bad.
If A2U2, pin 13 is at 16 MHz and line 2QC on
A2U2 (pin 9) is not at 2 MHz, replace A2U2.
If bad, replace clock controller A2U6 or 16-MHz
crystal A2Yl.
If bad, replace A2U17.
If bad, check for a 16-MHz signal at A2U6, pins
12
and 17. If absent, check A2Yl. Replace
A2U6, as required.