HP 9845 C with 280 option startup failure

Tequi Lizer tequilizer at gmx.net
Fri Nov 4 14:34:00 CST 2005

> Is this the PSU that's shown in the boardswapper manual? It doesn't give 
> much detail (for some odd reason you replace the complete PSU, not just 
> the faulty board...), but there are a couple of pictures of it.
Yes, it is the one in the boardswapper guide. In this special case, it 
is a "complete assembly exchange" guide.
>> The color monitor has just enough space for one additional board, the=20
>> light pen controller. Since I don't have the controller board, I=20
>> currently don't care much about a light pen, although it would be nice=20
> I don't have one either. It would be nice to find for completeness (if 
> only to 'complete' the schematics), but....
> It's clear the light pen was fairly hardware-intensive. Many of the video 
> timing signals, including the outputs from the horizontal counter on the 
> text PCB, go to the light pen controller.
The light pen itself is a fairly simple piece of hardware, but the 
controller of course needs all information to determine the current 
position of the crt beam (which is not that easy in case the screen is 
dark, they used a workaround with a moving cursor for that).

>> to see how it works. However I got a working graphics 9111A tablet,=20
>> thats ok for now. Even a hopefully working 8"-floppy. So data transfer=20
> A 9885? I have a few of those....
No, I've got one of the double-sided double-drive 9895A.
> My 9845B came with a 3rd party mass storage ROM module. I am told this 
> allows the use of HPIB disks (probably Amigo protocol). The main use of 
> it so far has been due to the fact that it was a little PCB with normal 
> chips on it, not an HP hybrid. Very useful for figuring out what the ROM 
> module connections are.
The 3rd party ROM is probably more useful than the original HP ROM, 
since it should support the newer amigo-drives as well, not only the 
drives up to 9895A (as does the original ROM).

> I've heard from Dave recently, he claims to have scanned said diagrams. 
> Probaby time to pester him again :-)
> -tony
Thank you for the hint, I'll try again :-)


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