test-drb September 2006

test-drb@ccmp.vtda.org

200 participants
374 discussions

by ajp166＠bellatlantic.net

> >Subject: PDP-8m Console Switch Problems > From: Don North <ak6dn at mindspring.com> > Date: Wed, 06 Sep 2006 01:11:51 -0700 > To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org> > Cc: cctech at classiccmp.org > *****some snippage done.... >Of the front panel switches, DEPOSIT, EXAM, CONT all work fine. >The CLEAR, EXTD ADDR LOAD, and LOAD ADDR switches are nonfunctional. > >What I see is strange behavior in the debounce circuit, and in fact >the debounce circuit itself is one I have never seen before (and IMHO >the designer should be hung by his entrails). > >In ASCII art, here is a synopsis of the circuit: > > +5V +5V 1/6*7404 > | 1/4*74S175 | |\ > / +-----+-----+ | \ to > 470 \ GND--| Dn Qn |------| >O-----9318 > ohm / | | | / priority > \ GND--|>Clk QBn |O--+ |/ encoder > | | | | > +-------------o| MR~ | | > | +-----+-----+ | > | | | > __O ADDR GND | > O-/ LOAD | > | O------------------------------+ > | > +----+ > | > __O XTND > O-/ LOAD > | O---------->QBn... > | > +----+ > ... > | > __O > O-/ DEPOSIT > | O---------->QBn... >GND If you understand TTL and specifically TTL FFs then this is both logical and sane. Most NON-BUFFERED (74x74, 74x174, 74x175) D-FFs the output is fed back to the opposites input so any overload or transient to ground or Vcc (not safe for device) at the output will affect the devices state. Obviously if either output is "forced" to a state the other will follow inverted. The caveat is if either input cannot change due to internal failure or external logic failure the state will not change but you may see pulses when it tries to change. Pulling to ground is is safe as the output current (top transistor) is limited where the lower transistor can conduct hard. Unorthodox looking but, completely legit. You would get the same effect using a pair of (two from) inverters (7404 for example) cross coupling them and putting a switch across the outputs to debounce the switch. Bottom line is it worked for 30+ years and something else is broken. Now one of the things I've seen with older TTL is inputs that are stuck (likely ESD or other on die failure) to either Vcc or Ground. This could be either the '174 or the gate/inverter they drive is failed this way. >I've replaced the top 74S175 device (originally a Signetics 74S175 >date code 1970) with a socket, and have tried other 74x175 parts >but none work at all (NAT 74LS175 1983, TI 74AS175 1986, SIG 74S175 >1984, TI 74175 1974). Even on the bench in a proto board I can't >get any of these devices to behave like the original. Yanking the >QB~ output to hard ground does not force the Q output high. So >was DEC relying on the aberrant behavior of a 1970 Signetics 74S175? No, I've done this with TI, Signetics, National and others. >I'm about ready to rip out the two bogus '175s and replace them with >some other logic (three '00s if I calculate correctly). > >Anybody have any other ideas on what to look for or at? Check the down stream logic for stuck inputs. When I repaired my 8f (1973 manufacture date) I had several gates with the inputs stuck (the driving gate was ok) where the input was hard high or hard low at the pin and it was the gate itself not driving logic at fault. A milliampmeter confirmed one gate (7400) with pin 1 hard to VCC (Iol was >100ma). Drove me nuts as the first part replaced was a 7474 driving that gate with no fix! I'd give the 7404 the hairy eyeball! A quick test is socket a '175 with the Q and /Q output pins floating and using a jumper to ground make it flip [It WILL NOT IF MR/ is asserted, you can bend out the MR/ pin to avoid that.]. Then test the '04 for input changes output. Allison

19 years, 1 month

F/S HP 9830A system

by halarewich＠gmail.com

Hello I have for sale a hp9830 calculator/computer system wich includes the hp9830A with some extras from infotek(not sure what), a infotek fd-30 mass memory unit, a hp9862A calc plotter, a hp9866A thermal printer, a hp9869A card reader, all the cables, extra paper for the printer box of extra cards for the reader some cassette tapes for the 9830 hp sys test cassette a hp math pac vol 1 cassette ) all the io hookups 4 the printer plotter card reader and the infotek mass memory unit. plus the following manuals sys test instruction manual dated may 8th 1975, quick ref tp 9830Abasic july 1 1975, plotter control rom manual, printer manual, hp9830A 11272Bextended i/o rom manual, plotter pac, 11274B string variables Rom manual, 11270B matrix operations rom manual, 11278Bbatch basic rom manual, math pac manual, 11279B Advanced programming I rom manual, 11289B Advanced programming II rom manual, 11202A I/O interface Instalationb and service manual. If anybody wants any of this let me know if not clamed in a couple weeks its going to E-bay pictures will be up soon Chris Halarewich

19 years, 1 month

Anyone have a datasheet for a Mostek MK5002 4-digit counter/display driver?

by ethan.dicks＠gmail.com

I have a couple of ancient modules on the shelf here - they are the size of an old 3.5 digit DVM module with 4 MAN71 7-segment displays - I have figured out that the main chip is a Mostek MK5002 counter/display driver, but I can't find any data sheets on Google (just auctions for the chip). I'm guessing that it might have been used in some sort of pinball or arcade machine because of some of the hits I've gotten, but I'd just like to be able to reverse-engineer the pinout of the edge connector on this module. Thanks for any pointers, -ethan

19 years, 1 month

SGI -> Mips/Irix EOP'd

by compoobah＠valleyimplants.com

Joost wrote >They're a storage company now, IIRC. SGI's going to be adding some machines that are unlikely to be ontopic for many years yet in partenership with BOXX. Not a complete repeat of the VW series, these run Linux. Whee. Here's hoping they get enough back on their feet to get something interesting out again.

19 years, 1 month

Wilmington, Delaware USA Vintage Swap Meet - Oct 7th 2006

by billdeg＠degnanco.com

Only one month away! 2800 square feet of hard-to-find "classic" computers (pre-internet age), gaming, test equipment, parts and supplies, software, electronics, manuals, and more! DATE: October 7 WHERE: 504 Market Street 2nd floor / Copeland Room Wilmington, Delaware 19801 EVENT STARTS: 10AM EVENT ENDS: 4PM Details: http://marchclub.org/swapmeet.cfm http://marchclub.org/swapmeet_listing.cfm

19 years, 1 month

Heathkit H27

by Gary＠realtimecomp.com

Hey! Finally a question I can answer! > Can the H27 (dual 8" floppy drive) be hooked up to an H8? Or was that > strictly an H11-only device? No, the H-27 was strictly for the H-11. I believe it has a built-in controller (Z-80 based, if I remember correctly) inside the H-27 unit itself. The controller card for the H-11 (or PDP) was a glorified parallel interface. > > Of for that matter, can an H27 be hooked up to a non-heath Micro PDP11? > You could always by-pass the built-in controller in the H-27 box, and just interface to the bare drives. Gary

19 years, 1 month

Transformer question (only slightly OT)

by ajp166＠bellatlantic.net

> >Subject: Re: Transformer question (only slightly OT) > From: ard at p850ug1.demon.co.uk (Tony Duell) > Date: Tue, 05 Sep 2006 00:07:10 +0100 (BST) > To: cctalk at classiccmp.org > >As a result, I feel wall-warts are dangerous in the UK. They do not >contain na internal fuse, so could in theory draw nearly 30A from the >mains before the circuit fuse failed. The mains transformer primaty of >the wall-wart is supposed to burn out in a safe way, my experience >suggests this is not always the case. Wall warts, least here in USA must be fused internally or have a thermal interupter (usually the blow open). I've forcably opened a number of warts to replace protective devices. For many projects I use a standard 12V regulated DC wart and if higher voltages are required a simple multivibrator or switching regulator driving a suitable hunk of ferrite does nicely. It allows me to work inside without scary high potentials floating around and also solves the problem of "the right transformer". If warrented I bury the HV system in a seperate enclosure on the chassis and bypass the leads so the switching noise is hidden and in the case of tube (valve) designs keeps it looking "correct" while saving the annoying and sometimes messy job of winding a custom mains transformer. >I _never_ use wall-wards plugged straiht into the wall. Putting them on a >fuesed extension lead is somwhat safer. Altough personally I prefer a >decent transformer with fuses in both priamry and secondary circuits. Not a bad thing to do even here. Though I do it to assure all the warts are powered OFF when not in use not so much for safety but wasted power (electric bill). >> Another thing to have on your shop outlets is GFI protection. It could >> save your life. > >It can also be a right royal pain when a main filter has enough >unbalanced current to trip it. Ad it won't protect you if you're >relatively well insulated from ground but manage to connect yourself >between live and neutral or equivalent. Still it's some assistance for some cases. Perfection is a goal. >I use a GFI (RCCD, whatever it's called this week) in placees where there >could be dangerous leakage (sockets for outdoor appliances, in the >darkroom (a mixture of electrics and water, after all :-)), and so on. >But I don't have one on my workbence, nor do I want one. I have a mix of outlets on the bench some GFI protected some not. When I'm testing and working on line powered gear I used the GFI protected. Items that are known and in use I use the direct. Never hurts to have a good isolation transformer too. A recent addition to the bench power is a BIG RED BUTTON for those times when an unambigious off NOW is desired. Power safety is a good thing. Allison

19 years, 1 month

Heathkit H27

by ajp166＠bellatlantic.net

> >Subject: Re: Heathkit H27 > From: "Ethan Dicks" <ethan.dicks at gmail.com> > Date: Thu, 07 Sep 2006 12:30:11 +1200 > To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> > >On 9/7/06, Jay West <jwest at classiccmp.org> wrote: >> Can the H27 (dual 8" floppy drive) be hooked up to an H8? Or was that >> strictly an H11-only device? > >Dunno about the H8. > >> Of for that matter, can an H27 be hooked up to a non-heath Micro PDP11? Yes, if you have the heath interface card as well. If memory serves the standard RT-11 DX.sys was compatable. > >My recollection of debugging some H27 issues a couple of years back is >that there's a boot prom on the Qbus card for the H27. If that's the >case, then as long as it isn't stomping on a bootstrap ROM somewhere >else on the bus, then you should have no problems. Heath's card should >be register-level compatible with either the RXV11 or the RXV21 (can't >remember which one right now). The prom on card can be disabled. It worked well with 11/2 and KDF-11A cpus. The card is RXV-11 compatable. The big upside with the H27 is it would format 8" (RX01) disks. The downside is the drives, the spindle clamp was plastic and would dryout and crack. >My H-11 came with a KDF-11, DEC memory, pretty much DEC >everything; just the Heath backplane and PSU and floppy controller. >The previous owner never booted from floppy, though; he hacked the >case and added an off-to-the-side CD-interconnect and used an RLV11. Thats a ugly hack. Many were upgraded to 11/23 cpu, Q18 ram and some times DLV11j for more IO with fewer boards. >It took a bit of work to get it all back together. I'll bet. Test the PS well, the LVSMPS was not every reliable. Allison

19 years, 1 month

Heathkit H27

by jwest＠classiccmp.org

Can the H27 (dual 8" floppy drive) be hooked up to an H8? Or was that strictly an H11-only device? Of for that matter, can an H27 be hooked up to a non-heath Micro PDP11? Thanks for any advice! Jay West

19 years, 1 month

Help ID-ing DOS backup format

by cclist＠sydex.com

Folks, I received a couple of DC6250 backup tapes this morning. While writing a program to unravel the backup format looks to be pretty simple, I'd like to know what created these beasts. They're from a Windoze box circa 1995. The "GENERATION" right at the start might be a hint. Here's a dump of the first few bytes of a tape, hex on the left, ASCII on the right: 000000 47 45 4E 45 52 41 54 49-4F 4E 20 EC E9 C6 F3 F4 GENERATION 8T?=( 000010 F4 E5 C2 20 20 70 6F 73-5F 62 61 63 6B 75 70 5F (s- pos_backup_ 000020 32 39 30 38 39 35 20 20-20 20 20 20 20 20 20 20 290895 000030 20 20 20 20 20 20 31 30-3A 32 30 3A 30 31 20 33 10:20:01 3 000040 30 2F 30 38 2F 31 39 39-35 20 4E 20 20 20 0A 31 0/08/1995 N ?1 000050 30 20 31 20 20 20 20 20-20 20 20 30 30 30 30 20 0 1 0000 000060 30 30 30 30 20 43 3A 5C-0A 32 37 20 30 30 30 30 0000 C:\?27 0000 000070 39 46 34 36 20 33 32 43-30 20 31 43 42 46 20 49 9F46 32C0 1CBF I 000080 4F 2E 53 59 53 0A 32 37-20 30 30 30 30 39 34 46 O.SYS?27 000094F 000090 41 20 33 32 43 30 20 31-43 42 46 20 4D 53 44 4F A 32C0 1CBF MSDO 0000A0 53 2E 53 59 53 0A 32 30-20 30 30 30 30 44 35 37 S.SYS?20 0000D57 Anyone got an idea? It's not MSBACKUP, nor SYTOS. Thanks, Chuck

19 years, 1 month

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test-drb September 2006