It _is_ plug-and-play if you have the correct HP monitor. Otherwise it's rather less trivial. google....) a Fortunately Iv'e enver had to do this, both my 9836s came with the right monitors. But I have a fiar idea as to what is involved. The fitst thing is that the monochrome and colour monitors are very different. So different that you can't swap them over. The mono monitor has 2 TTL level signals (basically video and intensity) for the video input. The colour monbitor has 3 analogue signals (R,G,B - -at least thatbti ais as expected) -- and the machine outputs are current sinks, not votlage outputs. The pinout is dffernet too -- even the sync signals move around. So the first thign to do is to find out what sort of machine you have. _If_ it's no been messad around wioth (and this could be a big 'if'), then if you have a little thumbwheel control on the underside of the machine, left side, almostunder the vertical panel where the disk drives are, it's a colour machine (9836C). If not, there's jsut a slot there, it's a monochrome machine, (9836A). The only way to be really sure is to look at the video boarss. Take off the top cover (4 large screws on the bottom, not the smaller ones that hold the ekyboard in palce). Take off the board hold-down, then unplu tehe CPU board and disk controller, disconnect the signal cables from the disk crives. Next unplug hte power and LED cables from the drives and take out the drives themselves buy remvoign the 6 screws tht hodl each metal 'tunnel' in palce. Take off the metalwork under the drives. The video boards are hiding under the left disk drive. The top board is the graphics board, the bottom one for text. Check the part number on the board(s) and also if there are conenctors between the boards (other than the ribbon cables), it's a colour machine. he machins I own hav the follwoig nvideo boards : HP9836A (monochrome) Text : 09826-66576 Graphics : 09826-66577 HP9836C (colour) Text : 09836-66572 Graphics : 09836-66573 The monitor conencotr is a DA15. The pinouts are : Mono (HP9836A) 1 : Gnd (Intensity) 2 : Gnd (spare) 3 : N/C 4 : Gnd 5 : -12V 6 : Gnd 7 : +12V (Power to monitor) 8 : Chassis/ 9 : Intensity 10 : Spare 11 : Spare 12 : Video 13 : Gnd (Video) 14 : HSync 15 : VSync Colour (HP9836C) 1 : Gnd (B) 2 : Gnd (G) 3 : B/C 4 : Gnd 5 : -12V 6 ; Gnd 7 : +12V (for monitor power relay) 8 : Chassis 9 : Blue 10 : Green 11 : HSync 12 : Red 13 : Gnd(R) 14 : VBlank 15 : VSync I forget the scan rates, but I am pretty sure thay are odd. Well, VSync is 60Hz, or close to it. I think HSync is about 22KHz, but do check this, I may well eb thinking fo soemthing esle. If you ware goign to use a modern-ish LCD monitor note that a lot of thse can't sync that low. And even some of the ones tht include TV rates (15.xxx kHz) they won't sync to anything elxe below 31kHz. You mentioend you'd looked at the HP museum site. Which one? The one you want is the Australian museum, http://www.hpmuseum.net/ . One trap for the unwary here is that the HP9826 and HP9836 are very closely related machines, and many manuals for the latter aappear under the former on that site. When you have found outjsut what you have, I think I would start by measuring the frequencies of the sync signals o nthe ap[propraite pins of the DA15 connector. Then post here and maybe somebody will have some ideas. -tony

were I would certainly check. I've wasted far too much time based on false 'obvious' assumptions :-) You should open the machine up anyway to check for obvious falts (loose parts, signs of burnt components, etc. Testign the PSU on a dummy load is normalyl somethign I recoemnd doign on old machines, but it's not totally trivial for this amchine. The power supply consists of an unregulated DC supply digivng 20-30V (the mains trasnfoemr and smoothing capacitor are obvious, the rectifier is the TO3 can on the little PCB at the back that also holds the votlage selector switches -- this is not a power tranistor, its' a double diode). The output of this feeds the regualtor board giving +5V, +12V, -12V. This board plugs itno a conenctor on the case which arries the DC input and a connectr on the motherboard which carries the DC outputs to the rest of the machine. And of course the motherboard has electroncis on it, inclduign the programmed 8042 keyboard controller. With 3 machiens ot maintain (a 9826, 9836A and 9836CU) I found it worth making a test box for the PSU board. This takes in 20V from my bench supply. It has a pair of edge connectors to take the PSU board, dummy load resistors, montior lamps and sockets to conenct a votlmeter to check each output. But that is rather too much work for just one machien I think, and you may decide to risk it. Anyway, gettign back to the video side, in all cases the video is cotnroleld by a 6845 chip, so the syncs are only present after the CPU has intialised the video system .If you have a relatively late CPU board there's a row of 8 LEDs on it which give the self-test codes (And indeed failures). it's worth watching these as the machine starts up, The official service manual gives the codes, etc. now. THe vertical sync is a fairly noarrow pulse at 60Hz, and is quite dififuclt to see on most 'scopes. It's almost impossible to see 2 of them and measure the time ebtween them. You may find a frequency counter more use. about Let's find out what hte sync frequnecy is first, and which machine you ahve. If it's a -A, the video is 2 TTL signals. 'My' schematics for the machine include the various monitors, the video circuitry of the mono monitor would eb a startign point for combining these signals to drive a more noraml monitor. -tony