22 Jul
2013
22 Jul
'13
3:36 a.m.
-----Oorspronkelijk bericht-----
Van: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
Namens Dave
Verzonden: zaterdag 20 juli 2013 16:25
Aan: General Discussion: On-Topic and Off-Topic Posts
Onderwerp: Re: HP 9830A always turns on with blank display
Second try at wrestling with the yahoo mail formatting . . .
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________________________________
From: Dave <dfnr2 at yahoo.com>
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Sent: Saturday, July 20, 2013 12:34 AM
Subject: Re: HP 9830A always turns on with blank display
Yes,
I actually picked up the HPCC DVD to get some of those. ?I have a I am glad you like them... There were also some
theory-of-operation
articles for the HP9800 series in the HPCC jorunal over the last
couple of years. But I rather glossed over the power-on circuitry ans
I felt it was not likely to be much of a problemn. Oh well...
to Datafile, but for some reason never received the
first
2012 issue. ?I suppose I have to wait until the next DVD update. ?I
actually am
much more comforted having the schematics, but I like
the articles because
there is frequently some subtlety that's not obvious without scoping, and
I
learn
something by going through the circuit description
while looking at the
schematics.
effect.
OK, first question. Is STOP the only key to do
this? WHat happens if
you
Only the STOP key. ?I had pushed various other keys earlier with no power up and press any otehr key?
?The only reason I went back an tried the STOP key is
because it's in the
operator
manual. ?I was surprised by this directive, as I would
expect only one
behavior on
power up. ?After than, the machine works as normal.
I would be most grateful for that.
>
>>Ah.. Init/ (power-on intialise signal) also clears the interrup flag
>>latches on the I/O interface PCB. Perhps for soem reason the
>>interruppt line (KeyDn/ on the schematics, as that's all it was usef
>>for in the HP9810, and that's the machine I worked on first) is being
>>set at power-on. That will cause interesting probkems with the machine
>>tryign to exectue the interrupt service route far to oarly.
>>
>>A few quick things to try. Pull out the tape contoller boards. As
>>others have mentioned there is a power-on init circuit there too, The
>>tape controller boards are the 4 with one blue handle behind the
>>display. You may have noticed that the board handles give the last 2
>>digits of the PCB part number using the obvious code. Anyway, the
>>machien wil lrun without the tape controlelr boards. So try it now, does
it
give
>It is curiouse that pressing a key has this
effect. The power-on
>circuit resets the microdoe program couter (OK, it actually sets all
>the address lines, the first address of the microcode [1] is 1 111 1
>111 or 1717 in 'split octal'). The STOP key clears a few latchies on
>the I/O interface, not much more.
>
>[1] Let me know if you want a commented source to the 256 word CPU
microcode.
a prompt at power-up.
I thought about that, and tried removing all the tape controller boards
and,
for
good measure, all the option ROMs. ?No change.
I will have to try that when I get back as well.
>Thanks!
>
>Dave
>
>
What I don't get, the compleet 9830 is on the HPCC DVD, and that's not the
DVD from the HP calculator museum.
But you also can download all the diagrams form the hp computer museum site,
www.hpmuseum.net.
What's also very helpful was for my, when I was (with the help and advice
Nest disconnect the keyboard (paddleboard in front
of the display PCB
--
I will try that when I get back home next week.
leave the in-like AMP connetor pluged in, it
conencts the mains switch.
Power up again, do you get a dispal ynow. If so, suspect a problem on
the keybaord enocder.
Most likely neither of these is the problem, the
problem is the Init/
circuit on the PSU board. It's based roudn a 74121 monostabl IC. I
would suspect the pair of 6.8uF capacitors associated with this IC.
-tony
from Tony) fixing my HP 9830, were the HP patents from
Eric's site
http://www.brouhaha.com/~eric/hpcalc/patents/
The patents tells you a lot about how the machine works and how the firmware
and routines are build and what they do.
-Rik