HP 900 model 300 monitor

Tony Duell ard.p850ug1 at gmail.com
Sun Oct 1 12:17:13 CDT 2017

On Sun, Oct 1, 2017 at 6:09 PM, js--- via cctalk <cctalk at classiccmp.org> wrote:
> On 10/1/2017 12:02 PM, Tony Duell via cctalk wrote:
>> On Sun, Oct 1, 2017 at 5:18 PM, js--- via cctalk<cctalk at classiccmp.org>
>> wrote:
>>> You need a 25khz monitor.   Here's a list I've compiled over the years.
>>> 25khz 640x400 SOG monitors
>>> HP 98204A (used with 82913A 12" 640x240 and 82912A 9" 640x240 monitors)
>> Are you sure about that one? The HP98204A that I have gives TV rate
>> composite
>> video, and those 2 monitors are re-badged NEC composite TV rate monitors
>> with AFAIK no internal changes.
> Those two are TV rate as you say (240 lines is the giveaway).  I just had
> them in there to remind me what NOT to use for 25khz.

FWIW, those monitors are also the 'official' ones for the HP86B. the 82163 HPIL
video interface and the (rare-ish) video interface for the Portable+

My worry was that the OP would get one of those monitors and find it still
doesn't work with his HP9000.

>>> HP 98204B (used with 35721 14" 640x400 and 35731 12" 640x400 monitors)
>> That' the one I know. I've go the HP35731 monitor and hope never to have
>> to repair it agan. It is painful to work on!
> I have both the 35721 and the 35731 here to repair.  Yes, the 35731 is no
> fun to take apart.  The late, very kind Jon Johnston sent me the innards of

First trap for the unwary is getting the case off. You have to remove the CRT
bezel and then 2 hidden screws at the top under it. Don't ask how I found
that out....

My 35731 died with clouds of magic smoke. Fortunately just the mains filter
capacitors so it was fixable once I'd got it apart. An irritating
feature is that
all the connections between the mains transformer and the PCB are plugs
and sockets apart from one wire so you either have to remove the transformer
to get the PCB out or desolder said wire at the back of the voltage selector.

Oh yes, I had no end of problems with the input RCA sockets. In the end I
removed them, cut them off the brackets and mounted new sockets into the
resulting holes in said brackets before soldering them back in place. That
cured it!

I've never worked on the 35721, is it similar inside?


More information about the cctalk mailing list