test-drb November 2005

test-drb@ccmp.vtda.org

255 participants
692 discussions

by ajp166＠bellatlantic.net

> >Subject: Re: FPGA VAX update, now DIY TTL computers > From: woodelf <bfranchuk at jetnet.ab.ca> > Date: Fri, 11 Nov 2005 23:12:46 -0700 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > >The quick logic alu design is about 20 TTL per bit and Must only be using 7400 and 7404s doing it the hard way. As far back as '68 ALU blocks were availble, sure they cost $4 each then but the chip savings was there. >I am planning 18 bits wide... say 50 ents each for a 74XX gate that >is $10 per bit. >Rounding that to 20 bits that is $200 for the logic. Good sockets are >$.50 so >about $200. Not knowing PCB layout say a square inch per chip ... 20 >sq inches >@ 75 cents a inch ... $300 for the PCB's ... That is where my money >is going. >OH well I have all next year for that project, but I have two goals >for the ALU >and Control so I can have feel for what the 60's Computers were like >size wise. >1) 14 pin DIPS. 2) 7400 logic. Likely you'll never build it. Moving up just one step integreation wise is the 7483 (it equivilent is PDP8 era) full adder. That alone will cut the ALU chip count. My fun was not replicating the archetecture in an acient way but using the most MSI TTL parts I could get to replicate it in a moden way. IE: can I build a TTL PDP-8 with 1kx4 MOS ram in minimum TTL count for everything else. One can simplify that to working replica rather than exact replica. The difference is 2 'ls273 for a 16 bit register or 8 LS74s. But it goes further with fewer sockets, pins and wires, power and debug time. That also relects reliability once working as used parts are going to be a bit shakey untill (re)infant mortaility is again worked out from removal stresses. That may be minor but with a 200-400 peice TTL system you would be surprized unpleasently with how bad bring up can be if there is any uncertanty in the parts used. When I did the 200 peice TTL system it was 1972 into 73 and we were using the then common silicone plastic TTL aka the gray plastic and those were not reliable. That system took over a month to debug between wiring errors, timing errors (races and spikes) and new but partially dead chips. and after it was working for about three months after it was cranky when hot till we weeded out a few more bad actors. One thing I'd suggest for those building something greater 50 TTL is lots of LEDs to indicate the state or status of a block of logic plus the ability to slow the clock if possible to near DC so you can watch it do stuff without a fast logic analyser. It's a great fault finding tool. >I can get a 200 watt PC power supply ... 5 volts @ 20 amps that I >hope is ample PS. As for getting 7400 off scrap boards, if I had >the scrap boards I would most likely try to get the scrap item working >again. :D Theses days free PC power supplies (usually free scrap AT form factor) and cheap brick form factor switchers make 20A at 5 volts a trivial deal. Allison

18 years, 8 months

INCAA - PIT

by thomas.seidel＠gmail.com

Hi, a colleague just picked up the board of an "INCAA PIT" and handed it over to me. Looks like a programmable interface converter, it has two DB25 connectors and a 6800 CPU. The two ROMs are labelled "PIT 1985" and there is a bit of RAM (SRM2064 & TMM2016) . What is the box doing? Are there any manuals available? It's possible to program the CPU via the DB25 connector? Any hints? TIA, --Thomas

18 years, 8 months

That darn Intel jingle...

by julesrichardsonuk＠yahoo.co.uk

OK, so there goes that irritating Intel jingle on yet another commercial for a product featuring one of their chips - thus ensuring that I'll make darn sure I shop around for alternatives before ever considering one of their chips. It did make me think though; has computing history been littered with ads containing trademark features which are so annoying (in an audio or visual sense), or is this a recent thing? (For some reason the 'Playstation noise' isn't nearly as grating...) cheers Jules

18 years, 8 months

LA210 Schematics

by ajp166＠bellatlantic.net

> >Subject: Re: LA210 Schematics > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Sat, 12 Nov 2005 01:54:04 +0000 (GMT) > To: cctalk at classiccmp.org > >> >Easiest starting point is to check operating voltages. If during >> >printing they drop or go flakey it's the PS. The fact that it >> >prints at all says most of the logic is solid and working. >> > >> >Allison >> > >> > >> > >> > >> One of the reasons I want some kind of schematic. >> >> So I can know what voltage levels should be where, and if I find > >There pretty much has to be a +5V line for the TTL, microprocessor, etc. >You can find that from data sheets on some of the ICs. I'd start by >checking the voltage between that and logic ground (found on the gnd pin >of similar ICs). > >-tony Easier than that Tony. Pick a voltage on any line and when it start printing see if it changes when the printer fails. No need to know what the correct voltage is when it prints because it is likely correct at that time. However if the printing stops and the voltage does too then there is a clue. FYI: LA210 has a main logic with everything and a power supply unit of the switching variety. I do believe there is a power Ok signal >from that supply. I believe it's derived on the logic board. How if I knew which DEC prints box of the four it's in I could go further. Allison

18 years, 8 months

Help identifying a Motorola transistor (in HP 7908 PSU)

by david_comley＠yahoo.com

I have been trying on and off for a while to map out the schematic for the PSU of an HP7908 disc/tape unit. There's a transistor I can't identify on the board and I am wondering whether anyone can ID this thing for me. The markings show "239" and then the batwings, and then below that it says "4-456". Same problem for a number of the diodes that are labeled "GE010673". Thanks - Dave __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

18 years, 8 months

HP7245A ROM problems?

by ard＠p850ug1.demon.co.uk

I am working on an HP7245A thermal printer/plotter. I have a home-made schematic of this unit, and have read the service manual for the -B version on hpmusuem.net OK, a bit of history. It was given to me because the previous owner couldn't get it to work and suspected a PSU problem. In fact I don't think there's much wrong with the PSU (off-load, all outputs are correct), I think the logic side was trying to drive one of the motor windings hard on, and that was tripping the PSU. Currently, I've got it in bits. I've removed all the mechanical side. I have the backplane, 4 internal logic boards, HPIB interface and PSU plugged together. I've also got the the ribbon cable plugged into the I/O PCB and to the front control panels. I am trying the self-tests. I am assuming they are similar to the ones in the -B model, and that all test LEDs on (77(8)) is a pass, for example. And that the tests are in the same order and do the same things. Test 1 (processor board buffers) seems to pass Test 2 (ROM) doesn't, see below Test 4 (RAM) passes, even though the darn thing uses 2114s Tests 5,6,7, (interrupts) seem to pass too Test 10 (HPIB) passes. And I see little flashes from the 'addressed' LEDs on the back, so I think it is doing something to the HPIB card. OK, back to test 2. This would seem to be a ROM checksum test. It fails with error 54(8). It's certainly looking at the ROMs on the ROM/RAM (memory) PCB), if I pull that board it fails with a different code (which, if the codes are the same as the -B version would indicate that the lowest ROM on the ROM/RAM board had failed, which makes sense as it's not there when I pull the board). Now for the problem. if the the codes are the same, then 54(8) is 'ROM 60 LSB failed). ROM 60 (assuming that's the high digits of the octal address, which makes a lot of sense) is a ROM that's not present in the -A model (the -B has more ROM, since it can do raster dumps). The ROMs are AM9216s. These seem to 2K*8 devices, with 2 chip select lines (at least one of which has mask-programmable polarity) and need a +12V supply (although not a -ve supply as well). Does anyone have a service manual for the -A model and can look up this error code for me. And assumign it is a ROM failure, does anyone have a ROM dump, or a dead machine I can get a chip (or board) from? -tony

18 years, 8 months

LA210 Schematics

by ajp166＠bellatlantic.net

> >Subject: LA210 Schematics > From: Kevin Handy <kth at srv.net> > Date: Fri, 11 Nov 2005 13:29:25 -0700 > To: "'General Discussion": "On-Topic and Off-Topic Posts'" > <cctalk at classiccmp.org> > >Are the LA210 printer schematics/tech info available anywhere? I have hardcopy buried somewhere I think. No B size scanner though. >I have one that will print a few lines, then go through some kind >of reset (printing, lights go off, come back on, loss of text, repeat) > >Self-test print fails after a few lines in like manner. Prints a few >lines, resets, and stops printing. You likely have a bad PS. Especially if it does it during self test. Easiest starting point is to check operating voltages. If during printing they drop or go flakey it's the PS. The fact that it prints at all says most of the logic is solid and working. Allison

18 years, 8 months

LA210 Schematics

by kth＠srv.net

Are the LA210 printer schematics/tech info available anywhere? I have one that will print a few lines, then go through some kind of reset (printing, lights go off, come back on, loss of text, repeat) Self-test print fails after a few lines in like manner. Prints a few lines, resets, and stops printing.

18 years, 8 months

MSV11-LK (M8059-KF)

by dbetz＠xlisper.mv.com

Does anyone have documentation on the jumper settings for an MSV11-LK memory module? I have two and want to make sure they are configured correctly. Thanks, David

18 years, 8 months

MSV11-LK (M8059-KF)

by ajp166＠bellatlantic.net

> >Subject: Re: MSV11-LK (M8059-KF) > From: "bill bailey" <beclassic at att.net> > Date: Fri, 11 Nov 2005 17:22:27 -0500 > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >David - Maybe Ashley Carder can locate the copy he got from me with the >11/23. > >bill bailey > > >----- Original Message ----- >From: "David Betz" <dbetz at xlisper.mv.com> >To: "General Discussion: On-Topic and Off-Topic Posts" ><cctalk at classiccmp.org> >Sent: Friday, November 11, 2005 4:31 PM >Subject: MSV11-LK (M8059-KF) > > >> Does anyone have documentation on the jumper settings for an MSV11-LK >> memory module? I have two and want to make sure they are configured >> correctly. >> >> Thanks, >> David If you can find a copy of the 1982 DIGITAL Microcomputers and Memories handbook page 506. You should really have a copy of than and any of the other pulp handbooks DEC did. FYI: the module is M8059 as some may reference from that rather than MSV11-LK. The trailing suffix covers parity vs nonparity and 128k VS 256K (jumper info applies to all MSV11-xx). Allison

18 years, 8 months

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test-drb November 2005