On Tue, Jun 8, 2010 at 10:40 PM, Mark Davidson <mdavidson1963 at gmail.com> wrote: Hey, I've got on of those! Except mine is 9826, with the built-in small screen and single floppy. Not aware of any addtional three digits to the number. I would be very interested to hear of your success in getting OS/program media for it. Mine turns on and lets me type in BASIC programs, but it fails to boot off any of the disks it came with. I have two rom carts in the back, I believe RS232 and HP-IB, which sounds pretty standard. This could be interesting. I wonder, does he have any spare monitors? I know your model requires it, but I;m not sure if mine allows one. Seems plenty flat on top to accommodate one. -- j

I forgot to mention that the machines are located in Largo, FL. Mark On Tue, Jun 8, 2010 at 8:40 PM, Mark Davidson <mdavidson1963 at gmail.com> wrote:

They are nice machines. I have 2 of them (a 9836A and a 9836CU) along with the closely-related 9826. And a couple of other machines in the range -- the 9816 (built into the monitor case) and the 9817 (a 'shoebox'). Anyway, back to the 9836. To get inside, there are 4 large screws on the underside. The top cover then lifts off. There's a motherboard flat in he bvottom of the case, which as well as connectors for the other boards, contains trhe HPIB, keyboard controller and some of the address decoder circuitry. Plugged into the motherboard are the expansion backplane (8 DIO slots), the CPU board, the floppy controller and the PSU regulator. There are 2 more PCBs under the left-hand disk drive which are the video display circuitry (the top board is for the graphics display, the lower board for the text display). Several CPU boards have been used in these machines. Most of them contain a 68000 CPU and some RAM (which is auto-addressed [1]. And the boot ROMs. If at all possible, get a machine with boot ROM 3.0 or later. Those can boot from any device (internal drives, HPIB drives, SRM network, even bubble mmemory (!)) whereas older versions of the ROM can only boot from the internal drive. I believe there is a boot disk (it's part of the SRM system) that allows older machines to boot from anything, though. And note that alas the later ROMs are larger than the older ones, so it's not simply a matter of getting the images and burning a couple of EPROMs to upgrade an older machine. [1] In these machines, RAM starts at the top of the address space and builds down. The expansion RAM cards have to be addressed by DIP switches. At part of the power-on self-test, the machine scans down throught the RAM. When it fails to get a DTACK/, then hardware on the CPU board automatically sets the address of the RAM on the CPU board to fit immediatately below all the RAM it's found. The latest CPU board contains no RAM, but it does have a 68010 processor and an MMU circuit. This is fitted to the -U machines (U == Unix, these machines can run HP-UX). If you have this board, you need at least one expansion RAM card. The floppy cotnroller uses a Western Digital IC. A couple of points. Firstly, there are spearate cables from each drive to the controller board. The drives have their MX jumpers fitted, so the outputs are always enabled. The controller monitors things like the WrProt signal from each drive to detect disk changes. The cable for drive 0 is soldered to the board, the one for drive 1 is plugged in. This is because the same cotnroller is used in most single-drive 9826s, whereupon the drive 1 cable is not fitted. There is a 256 byte sector buffer on the disk controller board. It's a pair of either 2112s or 2114s (with 2 address pins grounds). I mention this becvuase if you hve the latter RAM and have internal disk problems, you know where to look :-) (Yes, I did have this problem on my 9836CU). The power supply is quite friendly in some ways, but a paiu to test on dummy load. The basic design is that there's a transformer, a little PCB at the back containing the voltage selector switches and a rectifier (the TO3 can is a double diode, nothing more), and a smoothing capacitor. This gives about 30VDC to the regulator board which contains swithcing regulators to produce +5V, +12V and -12V. The problem comes in testing it. The regualtor board has 2 sets of edge figners. One plugs into a chassis-mounted connector carrying the DC input carries the outputs. Now, since the mothrboard contains considerable circuitry, including a programmed 8041 microcontroller (for the keyboard interface), you don't want to use that as a dummy load. What I did was make up a test box. A die-cast box with a couple fo edge connectors on top, load resistors, lapms and voltage test sockets on all the outputs and a pair of input sockets to power it from my bench supply. Then I can just plug the PSU regualtor board in that and run it out of the machine. But hten I have 3 of these machines to maintain. It's probably too much work to do if you only have one. A few comments now on the 9826 in case anyone has one. It's very similar inside. Early models had a floppy controller that could only handle one drive and a lower-current PSU, but I have never seen these. Most of them have the same boards as are used in the 9836. The video system is very different, of course, (a monitor PCB -- which contains just the horizontal and video amplifier cirucits, the vertical circuit is on the text video PCB) mounted in the base of the machine in front of the motherboard, a text video PCB standing vertically behind the CRT and a graphics board on top of that, screwed to the top of the CRT cage. A word of warning. The CRT in the 9826 is _not_ rimbanded (the ones in all 9836s are). If you have to work on the CRT area of the machine, take great care, an impolosion is likely to be unpleasant. As for expansion, there are 8 DIO slots. These uise the same connectors as the S100 bus, but different signals (obviously) and smaller PCBs. The signals are essentially the 68K bus with a few extras. 4 of the slots can take boards with external connectors (interfaces, etc), the 4 between them can take things like RAM, ROM, bubble memory, DMA controller, etc. These machines have a built-in HPIB interface, but nothing else. I think an RS232 interface (HP98626 or even better HP98628, which is Z80-controller and does intenral buffering) is almost essential. An HP98622 GPIO card (16 bit parallel in and out) is useful too. There are many other interfaces and add-ons, inclduing ROM boards containing BASIC or HPL, more HPIB interfaces, and even a bubble memory board. There's an HP serivce manual which is a boardswapper guide, but is probably worth reading. The only thing I really disafgree with in it (other than boardswapping :-)) is the procedure fro removing the CRT from a 9826. I find it a lot easier to remove the keyboard and then the bezele assembly, then put the latter face down on the bench, remove the CRT mounting band, and lift the CRT out. It takes alittle longer than the HP method, but it's much less likely to damage the CRT. There's also a set of unofficial schematics which may be useful if you have to fix the thing. You also want to read the manauls for the language you are using (probably HP BASIC 5.x). There are a lot of interesting features... On Bitsavers, you want to look at the _pascal_ system manuals. Some them cotnain a lot of low-level programming information. And the 'breadboard' interface manual which describes the DIO bus. As for software, be warned that he disk images on the Australian museum site are geernally for 3.5" disks. You can't dump them to 5.25" disks for the internal drives. If you have a HP9122 or similar (and boot ROM 3.0 or later) then there's no problem, you can boot from that and transfer the software to the interal drives later. Do watch the power-on tests. The error messages are not always taht clear, but they will pick up a lot of problems. If something eems 'not right' then you need to debug the hardware. Let me know if you need any help. I've done a bit with these machines. -tony