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8 bit isa lava parallel card in vintage ibm5155

The card you show resembles one of the dime-a-dozen Taiwanese import cards that used to be very common and probably the least expensive 8 bit ISA card that could be purchased. I probably have 2 or three of them--you could get them at computer shows for $5 or so back when. Surely, there must be some still around...

I'm just curious if you're doing something that requires a printer-compatible port. There used to be (and still may well be; I haven't looked), 8-bit ISA cards with one or more Intel 8255A chips on it. They were quite popular with the early instrumentation people. I have one such. You get the full set of 8255 ports that can be programmed any way you'd like.

Just a thought...
 
Chuck,

I had considered the 8255 IC, which were popular add ons for 8080 and Z80 micros because it does have three 8 bit I/O ports. But there is something about the simplicity an elegance of the printer parallel card with just a handful of 74LS series TTL IC's on it. I was also able to download the circuit for it and its base address can also be changed on the board with a link from H378 to H278, so I can use two of these cards in the computer at once.

I have always had a fondness for TTL DIL package IC's, especially the original 74 series of the late 1960's and 1970's and 74LS types. They are generally very reliable and this in many ways this is one of the things that attracts me to a computer like the IBM5155. The 54 series or mil spec equivalents used in Apollo spacecraft computers and were astonishingly reliable. Tektronix also list the TTL IC as being the most resistant IC to electrostatic discharge damage. My favorite TTL circuit (of all time) has no ROM, RAM or micro's in it, just over 65 TTL IC's and its amazing what can be done with just them:

http://worldphaco.com/uploads/LAWN_TENNIS.pdf

One of these Pong games made with plain TTL draws about 1.2A @5V, but only 360mA if its made with 74LS !

If you have a spare parallel card, I think given the quality of this sort of thing (in my opinion) its worth at least $25 (not $5) so if you can part with one, can you email me on the email shown on the link with the card image on it.

thanks, Hugo.
 
Hugo, my first ICs were RTL and then DTL. TO-100 and flatpack. I'm not aware that they were more reliable than the stuff we have today.

One thing you don't get with the printer port mod is a latching input; that may matter to you. Of course, an 8255 will give you both, as well the ability to repurpose pins on the C port. LAVA did have an 8255 board. Up until a few years ago, you could still get ISA triple-8255 boards from TeamETT in Thailand. Surely, I can't be the only one with one still in my card collection. They also made a PCI version--and National Instruments made a bucketload of those.

I'll look around and see what I can find--or you may want to take Stone up on his offer. I nowhere nearly as organized. Heck, I still have an Ampex Megastore SASI ISA card rattling around somewhere...
 
Chuck, It could just be personal experience, but over years of repairing TTL based pcb's it always seems that the plastic cased ones that fail (but only very rarely). I have yet to ever had to replace a single ceramic cased 74 or 54 series IC in any apparatus. But by comparison the cmos IC's of all kinds, especially the original 4000 series were shocking, failing inexplicably and in clusters. One thing they would do is get an output stage that goes totally open circuit, leaving the inputs of other IC's connected to that floating, giving all sorts of weird effects, and when you touch the connection with the scope, it discharges it, making it look like logic 0. Later cmos were much better protected from electrostatic damage though. I still have many TTL's IC's from the 70's, all working just like the day they were made. Recently though, for an exercise, I thought I would try out 90 year old transformers & tubes to make a 2 watt iPod amplifier. Astonishingly, still working, and as I remarked in the end of this brief article, what manufacturer these days would make components that lasted 90 years, probably the will last triple that:

http://worldphaco.com/uploads/UX-171-A_Class_AB1_push_pull_amplifier..pdf

I managed to work in a classic 1970's National LM309k into the project.
It appears these days that electrolytic caps set the limits on appliance lifetimes.
 
Yes that latching input feature of the 8225 might turn out to be handy. What sort of connector did the cards with the 8255 use?
 
Hugo Holden said:
Chuck, It could just be personal experience, but over years of repairing TTL based pcb's it always seems that the plastic cased ones that fail (but only very rarely). I have yet to ever had to replace a single ceramic cased 74 or 54 series IC in any apparatus. But by comparison the cmos IC's of all kinds, especially the original 4000 series were shocking, failing inexplicably and in clusters. One thing they would do is get an output stage that goes totally open circuit, leaving the inputs of other IC's connected to that floating, giving all sorts of weird effects, and when you touch the connection with the scope, it discharges it, making it look like logic 0. Later cmos were much better protected from electrostatic damage though. I still have many TTL's IC's from the 70's, all working just like the day they were made. Recently though, for an exercise, I thought I would try out 90 year old transformers & tubes to make a 2 watt iPod amplifier. Astonishingly, still working, and as I remarked in the end of this brief article, what manufacturer these days would make components that lasted 90 years, probably the will last triple that:

http://worldphaco.com/uploads/UX-171-A_Class_AB1_push_pull_amplifier..pdf

I managed to work in a classic 1970's National LM309k into the project.
It appears these days that electrolytic caps set the limits on appliance lifetimes.
Click to expand...

I've been working on- and off- rehabilitating a 70's dumb terminal. No microprocessor; all 4000 series CMOS (mostly NSC and SSS). I'll get a section working for a few hours. and then another one will fail. Very frustrating. So I put it to one side and pick it up a few months later after my frustration dissipates. For what it's worth, some of the Japanese 4000-series from the same time, such as Toshiba, seem to be pretty good.

I've still got a military receiver from the 1940s (last saw service in Okinawa in 1945) that I run with an old rack-mount Western Electric power supply. Works fine with absolutely no audible hum. But then, consider the telephone of the 1960s and earlier. Since (at least in the US) all were leased from Ma Bell, service life was important and the lowly 500-series desk set was designed with a service life of 50 years. There were some clever designs in those. For example, when the Touch-tone dialing came out, the electronics used a single transistor to generate the DTMF signals--and they were stable.
 
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