HP 9845 C with 280 option startup failure

[Tequi Lizer]

> OK, here's a pinout from the schematic.
>
>             Rear of machine, looking down into the edge connector
>             on the 98770-66534 board
>
>   MonAck/ --(  )-- WrFull/
>    MonStb --(  )-- DD15
>       Gnd --(  )-- MonClrAddr/
>       Gnd --(  )-- +5V
>     MD(6) --(  )-- +5V
>     MD(7) --(  )-- +5V
>     MD(4) --(  )   N/C
>     MD(5) --(  )-- -Vm
>     MD(2) --(  )-- -Vm
>     MD(3) --(  )-- +Vm
>     MD(0) --(  )-- +Vm
>     MD(1) --(  )-- Gnd
>     MD(9) --(  )-- Gnd
>     MD(8) --(  )-- MD(12)
>    MD(11) --(  )-- MD(13)
>    MD(10) --(  )-- MD(14)
>      DA14 --(  )-- Gnd
>       Gnd --(  )-- Init/
>
> Where : 
> +Vm = +18V monitor supply from mainframe PSU
> -Vm = -18V monitor supply from mainframe PSU
>
> DA14, DD15 are 2 blanking/control signals (derrived, sortof, from address 
> 14 and data 15), mainframe to monitor
>  
> Init/ = mainframe reset signal (to monitor)
>
> MocAck/ = Vertical timing signal from monitor text PCB
>
> MonStb = Charater strobe from monitor text PCB
>
> WrFull/ = Buffer full (to monitor text PCB)
>
> MonClrAddr/= Clear buffer memory address (end of line) from monitor text PCB
>
> MD(n) = 15 bit date word to monitor text PCB
>
>    0...6 == Ascii code
>    7 = chracter set seelct (or alternatively, 0..7 = character code :-))
>    8 = cursor at this location
>    9 = inverse video
>   10 = blink
>   11 = underline
>   12..14 = colour select (not used on mono monitor)
>
>   
Indeed pretty helpful. Matches to what I've found out.

Here it is with relation to the boardswapper guides:

NP/=MonAck/ --(  )-- WrFull/=FLB/
 NW/=MonStb --(  )-- DD15=GS
        Gnd --(  )-- MonClrAddr/=NL/
        Gnd --(  )-- +5V
   I6=MD(6) --(  )-- +5V
   CS=MD(7) --(  )-- +5V
   I4=MD(4) --(  )   N/C
   I5=MD(5) --(  )-- -Vm
   I2=MD(2) --(  )-- -Vm
   I3=MD(3) --(  )-- +Vm
   I0=MD(0) --(  )-- +Vm
   I1=MD(1) --(  )-- Gnd
   IV=MD(9) --(  )-- Gnd
  CUR=MD(8) --(  )-- MD(12)=RDA
  UL=MD(11) --(  )-- MD(13)=GRA
   B=MD(10) --(  )-- MD(14)=BLA
AS=GS/=DA14 --(  )-- Gnd
        Gnd --(  )-- Init/

where

NP = New Page (=> load start address + AS + GS from block 0 at address 600000 into address register)
NL = New Line (=> read one line from crt buffer into line buffer)
NW = New Word (=> provide next character+attribute data to monitor)
AS = Alpha Select (=> enable alpha display, used as GS/ for switching between alpha and graphics on the monochromes)
GS = Graphics Select (=> enable graphics display on the 9845C only, where alpha & graphics can be displayed simultaneously)
FLB = Full Line Buffer

For the 9845C, the +5V triggers the power-on procedure for the 98770A monitor.

For the 98780A, maybe the DA14 line is used to switch between a blinking/nonblinking cursor, identified as CURS signal. I assume that the MD12-14 lines are the ones that are not connected in that 98780A.

Quite interesting the INIT/-signal is looped through to the monitor.


> You really need the schematics :-)
>
>   
Yes, Dave Colver told me the CD is almost finished.


-- Ansgar