Drats. I had my computer set to mono and I did not catch this. It overdrives quite badly too. Let me see if TH-cam will let me fix only the sound. [Answer: not it won't, so I'll let it stand. Take good care of your left ear.]
@@CuriousMarc What editing program do you use? I have a plug-in for premiere that warns me when there is audio on only one track at any point in the timeline.
I use to work for Hewlett Packard in the Green Stripe operation doing component level repair on boards for the 9825. We had test ROM and RAM modules that fit into the option ROM slots. These bypassed the operating system and provided working RAM that allowed you to wake a dead system and provide a host of diagnostics to trouble shoot the system.
It's alive! Very impressive. Love the troubleshooting of actually understanding the circuit and replacing broken chips, not just throwing darts at the board replacing every part and cap you can find!
@@azzajohnson2123 Ha, I like that. At my old job (completely unrelated to electronics, but manufacturing engineering) we called it throwing darts, it was frowned upon. One guy actually said "we have a few more darts to throw" in a presentation once. Did not go well for him.
Well... So far as repair for hobby concerns, not everyone has the money to get the tools (like this super uber HP/Agilent logic analyzer) to make a proper diagnose analysis, specially in today's complex and speedy logics. And as for the "production" grade repair industry concerns... Unless is a super custom thousands of dollar board, makes more sense to just go and replace whole "lego" blocks on the system. Consumes less money... And what's more important, TIME.
That "Digi designer" breadboard thing is pretty slick! Good on you for sticking with it and thanks for sharing the process! The test circuit for the new chip really made it clear how it works.
Your channel is daily reinforcement of my stupidity. It’s like looking up at the night sky and seeing stars, so far away and incomprehensible. You and the people that help you are brilliant and have my admiration.
Great troubleshooting! Glad it's working again. Geez, two refresh circuits. Like discovering after years that your car had a 2nd steering wheel you didn't know about..
By looking at your efforts, I can't help but to think of the folks in the HP-department who build the 9825. The amount of paperwork, printouts and discussions back and forth just to be able to produce it is amazing.
I would just like to say that not only do you manage to be on the way to a complete repair, you do an impressive job of explaining it to an entertaining level. Such a joy to watch instead of all the cap replacers and alcohol sprayers you have on youtube as well. Thank you.
Thanks for the intermission. A smoke and a not so soft drink and I am ready to figure this all out! Excellent lesson in troubleshooting as always. Troubleshooting skill is something that I really feel some of us are born with, it comes naturally. For everyone else, they need to see and understand the though process a born troubleshooter goes through. You teach this better than anyone, and with a bit of humour.
Very interesting to follow how you are finding faults using logic analysers and other equipment! 😀 An alternate approach, especially since you are lucky to have another machine that works, would've been to acquire a thermal camera and image both the the working and faulty boards. Then compare and look out for chips that are either getting too warm or not warm when they should.
You did a pretty deep dive into the spaghetti logic. The simulator was a great tools for this. The fun part (for me) is actually re-tracing the design efforts by HP and getting a deeper understanding of how it functions. And now your an expert on internal DRAM refresh systems in HP 9825s :D Cheers,
Really wonderful to follow this. As a junior 'tech engineer' at HP I worked with a 'technical salesman' to sell these, just as they were beginning to be replaced. But for sure I never 'dived so deep' as you are having to go! Bravo!
This series feels like when you try to get out of a labyrinth but you have to make sure to go into every dead end before succeeding. But that's actually a good thing, because the dead ends are the interesting parts.
Very cool. I never knew how dynamic RAM refresh works. It is funny how something like you only have one working word of RAM can escape your attention until late in the game. Lesson is never assume anything. Excellent use of the simulation and breadboarding the controller tester. It must have been a challenge to figure out how to implement the internal counter.
Well, thank you for that masterful lesson on memory refresh. The Digiboard setup actually helped a lot to visualize the whole thing (besides the Logisim simulation). I am constantly astounded by your amazing skills. Thank you Marc for creating these videos!
It lives! This has been an awesome journey and HP really loves to over-engineer their stuff. Logisim is probably my most used program, it's an absolute life saver at times!
Figures you were able to get it going again. I mean, if anybody could, it would be you and your colleagues. After your work with the AGC, it’s not surprising at all. 😉
Oh man, this was immensely satisfying to see. The tester for the Intel chip was an excellent example. I can excuse the mono audio for the W on the dram controller. Hooray!
I have followed avidly the saga of the HP 9825. It's very interesting watching CuriousMarc and his colleagues patiently and tenaciously repairing this beloved unit. I cannot wait for part 9.
Magnificent trouble shooting - Incredible patience. I've never considered simulation as a repair tool. You uncovered a major flaw in the memory test routine. It's challenging to do a good mem-test that is not mislead by hardware problems. You'd like data width to be as big as address width which you have here. I'll bet HP didn't do production testing with this routine.
That logic sim was awesome. Love the breadboarding too. Really breaks down the woo woo magic of the chip for us :-) Nice to see it running again. A treasure for sure. It makes me want to troubleshoot my Apple IIe that I've been putting off
On one hand it sucks that the HP 9825 got zapped...but on the other hand, the silver lining is that it has provided an excellent series of videos on how the machine works and how to repair it.
Heck yeah! This episode has me grinning, and thinking of potential real world uses for my 4 digit BCD/Hex to Decimal display I built in college. Good work, keep it up!
Hats off to you Marc for making us understand this beautifull logic incorporated in those nice old machines. For me a bridge too far (my brain is analog lol) but I can follow everything you do.
Congratulations! That makes my long-ago repair of a Keronix CPU board look simple.... I'd been wondering for a while about the nature of the RAM test; now it appears that it is indeed the old "test each cell individually, and don't worry about testing the addressing" approach. By the time I started in the industry, making sure all the address lines were working was kind of standard, but the 9825 is from an earlier era when I guess people hadn't been burned enough by addressing failures to worry about testing for them.
If this series was an action movie this episode would be the scene where the hero is almost beaten, he is stumbling and about to go down. Them somehow he digs deep, summons some sort of inner strength and gets to his feet and defeats the bad guy leaving the audience cheering.
Nobody repairs the device as you do. My friend do repair industrial stuff this way: he writes down all the chips, buys all of them, replaces all of them and it always works. But this type of hp gear have got the heart and I fully understand your chase to understand how it works, how it thinks, how it lives. My friends way: cut a brain and replace whole dead body. Your way is to replace only the dead lungs (or something)...
It's so interesting how you can debug and examine these older machines. Just before things became so integrated that you could no longer really do so. As a software dev I have little idea how modern hardware engineers can design and debug modern hardware. There must be sooooo much reliance on simulation and using larger and larger blocks of known good designs. Probably similar to software dev in that regard.
where were you a fellow at? I was on a tiger team in phoenix. I remember the original plotter for the optical stepper masks that was in san jose, it was in a halon room with emergency breathing apparatus, did you ever see it? I seem to remember it was 20x20 feet, but I don't remember exactly.
I'm surprised that the calculator still has the original chiclet keyboard. They were replaced with a much nicer keyboard in the early 1980s. I worked with the 9825 and its successor the 9816 running 3060 board testers. They were almost indestructible and worked for decades. I wouldn't be surprised to still see them in production. They only weak point was the tape drive which had a tiny grain of wheat bulb used to detect the end of the tape. This would burn out and the tape would spin off the reel and it was a real pain to get the tape, and the elastic band driving and holding the tape on, back together.
Immense respect for sticking with this repair. Would that I had your magic powers, my pile of buggered test gear would be smaller.Thanks for another mostly incomprehensible video, logic to me is illogical, glad someone knows what it all means.....DA.
I am overwhelmed and mind-numbed by your heroic effort in repairing this ancient system. Quite an amazing amount of work. So I confess and apologize that I don't watch every minute of your videos. Thus have a tiny, tiny question. Is it a requirement that you must use this MEMORY CIRCUIT BOARD? In other words, fix it? I imagine you could replicate the entire function of this 2K monster with a raspberry pi zero. ($5)
An FPGA is another great way of replicating functionality. Or a Pi Pico, that way it doesn't need to boot Linux like the Pi Zero. Still, there's a kind of magic with old hardware, and it would be a shame to throw it out when it can be repaired.
Very very happy you get out of that mess! Congratulations Marc! But you still don't use tulip sockets after removing ic's and I think *that's a BAD THING* if you have to put your hands there inside again!
He worked on the HP 2645 terminal IIRC, based off an Intel 8080. Very nice expandable architecture, great video capabilities. That is as close to a PC as HP had. Actually it was a PC, but they did not want to market it as such - although they eventually released one with BASIC running on it towards the very end. And price point was very high. He wanted to make a single board version of that or something like that, but HP denied. Take it with a grain of salt, this is all hearsay/stories. If I ever meet him I should ask him.
Broadcom (which ultimately ended up with HP’s optoelectronics product line) still sells them, but they’re hellaciously expensive. (Around $40 for a 4-character module.)
This is like watching a newly released season of "24" and just dreading the wait until the next episode! =D You end up binge-watching all episodes of the old seasons just to pass the time! At the moment I am rewatching his HP85 videos where he is refurbishing gummy capstan wheels in the tape drive! :P
Hi Marc, while seeing your repair, HP 5004 signature analyzer came to my mind. Couldn't this tool be used for fetching good signature form working boards and compare then to the ones of the broken, to narrow down the faulty regions? But I think, to work with signature analyses, defined signals for triggering and gating have to be supplied by DUT. In addition, understanding what goes on is good any time. This logic simulation tool is super, thanks for your intro.
I really wonder how they did it, it’s so “illogical”. It looks like this might have been done piecemeal, they kept adding pieces until they covered all the corner cases. Or they were geniuses with three brain lobes!
Some may see all this work as a sisyphean task, but I love it ! Catching the 'look' of the dueling refresh logic was great insight! But my god all the test leads ... I'm curious how long it took to reset the testing apparatus after swapping out the chip?
What an intense journey this has been! Thanks for sharing it. If that board never fried, we wouldn't have had such an in-depth knowledge of the intricacies of Noodle Logic. Maybe you should take it easy for your next project, and do something simpler like, you know, landing a man on the moon =p
Marc builds chip " tester/display" just to show us how it works and confirm his theory. Seen only for a minute in the video, and yet it looks like something it would take me months to work out and build and yet you know he did it in one day,,, absolute legend... smh
I have an old logic trainer which is considerably bigger than that one, but I don't know if it's fully working or not and it has no brand on it either so I don't know who made it. It has enough switches and LEDs on it to control an 8-bit microprocessor plugged into the breadboard.
It would be a nice project to replicate the 3242: Three x 74x541 for the mux, a 74x590 for the counter and some additional gates for the control signals.
6:10 Audio shifts to left channel. I do that all the time in editing.
Drats. I had my computer set to mono and I did not catch this. It overdrives quite badly too. Let me see if TH-cam will let me fix only the sound. [Answer: not it won't, so I'll let it stand. Take good care of your left ear.]
Good enough for this neighbourhood!
@@CuriousMarc What editing program do you use? I have a plug-in for premiere that warns me when there is audio on only one track at any point in the timeline.
@@anonymousarmadillo6589 what plugin because I"m really tired of manually catching it.
spent 4mins fiddling with my audio thinking my right channel blew up. should have read comments first.
"obtw I was an Intel fellow once..."
Possibly the most understated flex in history ;)
I use to work for Hewlett Packard in the Green Stripe operation doing component level repair on boards for the 9825. We had test ROM and RAM modules that fit into the option ROM slots. These bypassed the operating system and provided working RAM that allowed you to wake a dead system and provide a host of diagnostics to trouble shoot the system.
oh that's a neat idea
Just like that "death mode" diagnostics cartridge which Adrian uses to diagnose his Commodore 64's on his channel repair videos...
It's alive! Very impressive. Love the troubleshooting of actually understanding the circuit and replacing broken chips, not just throwing darts at the board replacing every part and cap you can find!
@@azzajohnson2123 Ha, I like that. At my old job (completely unrelated to electronics, but manufacturing engineering) we called it throwing darts, it was frowned upon. One guy actually said "we have a few more darts to throw" in a presentation once. Did not go well for him.
Well... So far as repair for hobby concerns, not everyone has the money to get the tools (like this super uber HP/Agilent logic analyzer) to make a proper diagnose analysis, specially in today's complex and speedy logics.
And as for the "production" grade repair industry concerns... Unless is a super custom thousands of dollar board, makes more sense to just go and replace whole "lego" blocks on the system. Consumes less money... And what's more important, TIME.
@@hyoenmadan Specially with recent products, it's faster and cheaper to replace common problem chips and then go from there.
That "Digi designer" breadboard thing is pretty slick!
Good on you for sticking with it and thanks for sharing the process! The test circuit for the new chip really made it clear how it works.
Your channel is daily reinforcement of my stupidity. It’s like looking up at the night sky and seeing stars, so far away and incomprehensible. You and the people that help you are brilliant and have my admiration.
Great troubleshooting! Glad it's working again. Geez, two refresh circuits. Like discovering after years that your car had a 2nd steering wheel you didn't know about..
Success! Now Mr. Fancy pants can use his computer again :D
@@bobroberts2371 hmm that would be interesting, I wonder if he is still around!
It is even more difficult to put into one part his noodle brain.
By looking at your efforts, I can't help but to think of the folks in the HP-department who build the 9825.
The amount of paperwork, printouts and discussions back and forth just to be able to produce it is amazing.
Not to mention they had to design their own 16 bit hybrid processor and its 7 chips just to get started!
I would just like to say that not only do you manage to be on the way to a complete repair, you do an impressive job of explaining it to an entertaining level.
Such a joy to watch instead of all the cap replacers and alcohol sprayers you have on youtube as well. Thank you.
Thanks for the intermission. A smoke and a not so soft drink and I am ready to figure this all out! Excellent lesson in troubleshooting as always. Troubleshooting skill is something that I really feel some of us are born with, it comes naturally. For everyone else, they need to see and understand the though process a born troubleshooter goes through. You teach this better than anyone, and with a bit of humour.
I would like to see the face of Mr Fancy Pants when he gets the repair bill 😱
Run, rabbit run
Dig that hole, forget the sun
And when at last the work is done
Don't sit down, it's time to dig another one
Very interesting to follow how you are finding faults using logic analysers and other equipment! 😀
An alternate approach, especially since you are lucky to have another machine that works, would've been to acquire a thermal camera and image both the the working and faulty boards.
Then compare and look out for chips that are either getting too warm or not warm when they should.
Good job finding that bad memory controller. Having the tools to accurately simulate the hardware logic step by step is invaluable in debugging
You did a pretty deep dive into the spaghetti logic. The simulator was a great tools for this.
The fun part (for me) is actually re-tracing the design efforts by HP and getting a deeper understanding of how it functions.
And now your an expert on internal DRAM refresh systems in HP 9825s :D
Cheers,
Really wonderful to follow this. As a junior 'tech engineer' at HP I worked with a 'technical salesman' to sell these, just as they were beginning to be replaced. But for sure I never 'dived so deep' as you are having to go! Bravo!
This series feels like when you try to get out of a labyrinth but you have to make sure to go into every dead end before succeeding. But that's actually a good thing, because the dead ends are the interesting parts.
Very cool. I never knew how dynamic RAM refresh works. It is funny how something like you only have one working word of RAM can escape your attention until late in the game. Lesson is never assume anything. Excellent use of the simulation and breadboarding the controller tester. It must have been a challenge to figure out how to implement the internal counter.
Well, thank you for that masterful lesson on memory refresh. The Digiboard setup actually helped a lot to visualize the whole thing (besides the Logisim simulation). I am constantly astounded by your amazing skills. Thank you Marc for creating these videos!
It lives! This has been an awesome journey and HP really loves to over-engineer their stuff.
Logisim is probably my most used program, it's an absolute life saver at times!
I've been binge watching this series, I'm remembering stuff I'd forgotten and learning more. Thanks for making the series 🥳
To me, this was the most expected video of the week ! Superb job as usual. Well, cant wait for part 9 !
Figures you were able to get it going again. I mean, if anybody could, it would be you and your colleagues. After your work with the AGC, it’s not surprising at all. 😉
Indeed, period.
Are you going to decap the Intel chip, to see where exactly the magic smoke escaped?
Great idea, Ken Shirriff has to do the authopsy on the dead intel chip.
Yes, Ken Shirriff is on it.
@@CuriousMarc yes!! I am looking forward to this!!
@@CuriousMarc who'd have thought that eh ;-)
Oh man, this was immensely satisfying to see. The tester for the Intel chip was an excellent example.
I can excuse the mono audio for the W on the dram controller. Hooray!
I learn so much about troubleshooting from your videos! It's helped me in my job as a controls and instrumentation engineer!
I have followed avidly the saga of the HP 9825. It's very interesting watching CuriousMarc and his colleagues patiently and tenaciously repairing this beloved unit. I cannot wait for part 9.
Magnificent trouble shooting - Incredible patience. I've never considered simulation as a repair tool. You uncovered a major flaw in the memory test routine. It's challenging to do a good mem-test that is not mislead by hardware problems. You'd like data width to be as big as address width which you have here. I'll bet HP didn't do production testing with this routine.
That logic sim was awesome. Love the breadboarding too. Really breaks down the woo woo magic of the chip for us :-) Nice to see it running again. A treasure for sure. It makes me want to troubleshoot my Apple IIe that I've been putting off
Think this is best digital troubleshooting I have ever seen.
You're developing some Ben Eater type breadboard skills here ;-)
On one hand it sucks that the HP 9825 got zapped...but on the other hand, the silver lining is that it has provided an excellent series of videos on how the machine works and how to repair it.
Really good channel. I have no idea where you find the time to produce video's like these and troubleshoot this gear! Bravo!
I can hear Doc Brown shouting in the street: "IT WORKS!!!"
Heck yeah! This episode has me grinning, and thinking of potential real world uses for my 4 digit BCD/Hex to Decimal display I built in college.
Good work, keep it up!
Amazing debugging technique. I really loved the simulation you created to understand the memory board.
Hats off to you Marc for making us understand this beautifull logic incorporated in those nice old machines. For me a bridge too far (my brain is analog lol) but I can follow everything you do.
Congratulations!
That makes my long-ago repair of a Keronix CPU board look simple....
I'd been wondering for a while about the nature of the RAM test; now it appears that it is indeed the old "test each cell individually, and don't worry about testing the addressing" approach. By the time I started in the industry, making sure all the address lines were working was kind of standard, but the 9825 is from an earlier era when I guess people hadn't been burned enough by addressing failures to worry about testing for them.
Can barely wait for parts 9-15 of this excellent series! 👍😉
Hurrah it boots!!
Intermission Time really made me hungry and I started smoking.
If this series was an action movie this episode would be the scene where the hero is almost beaten, he is stumbling and about to go down. Them somehow he digs deep, summons some sort of inner strength and gets to his feet and defeats the bad guy leaving the audience cheering.
Marc - you are now Mr. Fancy Pants 2021 :)
Well done - I've really enjoyed following your journey on repairing the HP 9825 so far.
Last time I was this early, CuriousMarc didn't have his Magic Fancy Pants.
I have a pair - they're SUPER comfy!
Nobody repairs the device as you do. My friend do repair industrial stuff this way: he writes down all the chips, buys all of them, replaces all of them and it always works. But this type of hp gear have got the heart and I fully understand your chase to understand how it works, how it thinks, how it lives. My friends way: cut a brain and replace whole dead body. Your way is to replace only the dead lungs (or something)...
It's so interesting how you can debug and examine these older machines. Just before things became so integrated that you could no longer really do so.
As a software dev I have little idea how modern hardware engineers can design and debug modern hardware. There must be sooooo much reliance on simulation and using larger and larger blocks of known good designs. Probably similar to software dev in that regard.
also multi-GHz logic analyzers
the testing methodologies evolved alongside higher complexity ICs.
where were you a fellow at? I was on a tiger team in phoenix. I remember the original plotter for the optical stepper masks that was in san jose, it was in a halon room with emergency breathing apparatus, did you ever see it? I seem to remember it was 20x20 feet, but I don't remember exactly.
Nice work, a logical approach is usually the key to solving these complex problems.
I think that's why TRON "Trace On" is a famous movie. It helps you out of a big sticky situation. Fascinating. Thanks.
You know CuriousMarc is a tech guy first and a youtuber second when the test string he uses is "HELLO WORLD" instead of "LIKE AND SUBSCRIBE".
smash that "HELLO WORLD" load key, and Click CTRL-G :P
Really enjoying this series! So close to getting it all running again!
Marc , vous etes trop fort ! Le matériel HP des années 80 était au top niveau ! cher mais top niveau ! Your channel is really great !
Yeah! Great progress by now.. Only few steps left until all boards will be repaired.. 👍
Worked in the seventies on DGC Nova line of computers.
Large boards with about 150 IC's and no Logic analyzer, just a logic probe and analog scope.
Noodle Logic? Think that was one of my favourite Steely Dan albums back in the day.
noodle logic is most optimized for spaghetti code!
An Intel Fellow! Now we want to know more Marc!!
Now I'd like to see Ken fix that controller chip.
pretty sure its forbidden to show the process of replacing magic smoke
I’m finally starting to grasp the complexities of this troubleshooting after years of watching
That was a deep rabbit hole, if I've ever seen one.
I probably understand 10% of this at most (but more as I follow along) nevertheless I find this fascinating. Bravo Marc!
20:45 Great Elmer Fudd impersonation there
Marc, you have to wear the fancy pants again, Bravo!
Finally some positive progress! I was beginning to think this project was permanently stuck in reverse!
I'm surprised that the calculator still has the original chiclet keyboard. They were replaced with a much nicer keyboard in the early 1980s. I worked with the 9825 and its successor the 9816 running 3060 board testers. They were almost indestructible and worked for decades. I wouldn't be surprised to still see them in production.
They only weak point was the tape drive which had a tiny grain of wheat bulb used to detect the end of the tape. This would burn out and the tape would spin off the reel and it was a real pain to get the tape, and the elastic band driving and holding the tape on, back together.
This must have been an A originally, which then got upgraded to a B/T.
Immense respect for sticking with this repair. Would that I had your magic powers, my pile of buggered test gear would be smaller.Thanks for another mostly incomprehensible video, logic to me is illogical, glad someone knows what it all means.....DA.
I am overwhelmed and mind-numbed by your heroic effort in repairing this ancient system. Quite an amazing amount of work.
So I confess and apologize that I don't watch every minute of your videos. Thus have a tiny, tiny question.
Is it a requirement that you must use this MEMORY CIRCUIT BOARD? In other words, fix it?
I imagine you could replicate the entire function of this 2K monster with a raspberry pi zero. ($5)
An FPGA is another great way of replicating functionality. Or a Pi Pico, that way it doesn't need to boot Linux like the Pi Zero. Still, there's a kind of magic with old hardware, and it would be a shame to throw it out when it can be repaired.
If this series was a movie saga, it would be the extended cuts of LOTR. Glad it's finally working though!
"It wasn't that bad" he says 25:04 - how many weeks has it been though?? LOL
What a saga, brilliant work Marc! Noodles for lunch it is :)
Great fix and with an inexpensive chip!
I've never been this early for a Curious Marc video!
Very very happy you get out of that mess! Congratulations Marc! But you still don't use tulip sockets after removing ic's and I think *that's a BAD THING* if you have to put your hands there inside again!
I love that your channel is "Debugging best practice" Marc
Great Video! one of the best ones I've seen to date!
Interesting. Remember that Woz worked for HP. The Apple 2 interleaves ram refresh, processor and video with a minimal chip count.
He worked on the HP 2645 terminal IIRC, based off an Intel 8080. Very nice expandable architecture, great video capabilities. That is as close to a PC as HP had. Actually it was a PC, but they did not want to market it as such - although they eventually released one with BASIC running on it towards the very end. And price point was very high. He wanted to make a single board version of that or something like that, but HP denied. Take it with a grain of salt, this is all hearsay/stories. If I ever meet him I should ask him.
I love those small red dot matrix displays that hp used. Haven’t seen anything similar these days and I don’t consider the lcd’s a close runner up.
Broadcom (which ultimately ended up with HP’s optoelectronics product line) still sells them, but they’re hellaciously expensive. (Around $40 for a 4-character module.)
I’m glad it finally boots!
Really wonderful
Great job! Fun and interesting stuff!
I have a bunch of NOS Bi-Polar PROMS and a Data I/O 29B. Happy to burn a ROM if needed!
Super result so far! but did you fit the overvoltage protection crowbar circuit mod to the power supply yet?
I hope so. I'd hate for another "event" to do more damage.
Wow, what a journey!
This is like watching a newly released season of "24" and just dreading the wait until the next episode! =D
You end up binge-watching all episodes of the old seasons just to pass the time!
At the moment I am rewatching his HP85 videos where he is refurbishing gummy capstan wheels in the tape drive! :P
Congratulations for gain it back to life ....
You guys might invest in one of the Retro IC Testers. Can test TTL, RAM, etc. Very handy.
Learning so much on this series. Thank you.
Hi Marc, while seeing your repair, HP 5004 signature analyzer came to my mind. Couldn't this tool be used for fetching good signature form working boards and compare then to the ones of the broken, to narrow down the faulty regions? But I think, to work with signature analyses, defined signals for triggering and gating have to be supplied by DUT. In addition, understanding what goes on is good any time. This logic simulation tool is super, thanks for your intro.
25:23 Ken wanted to decap it eh :)
No doubt ! I thought the very same thing.
Staying awake until 2 am was worth it !
Great work! Can't wait for the next episode :D
The noodle logic designer had probably a hard time checking manually his state machine...
I really wonder how they did it, it’s so “illogical”. It looks like this might have been done piecemeal, they kept adding pieces until they covered all the corner cases. Or they were geniuses with three brain lobes!
I'm loving the octal.
Some may see all this work as a sisyphean task, but I love it ! Catching the 'look' of the dueling refresh logic was great insight! But my god all the test leads ... I'm curious how long it took to reset the testing apparatus after swapping out the chip?
It Is ALIVE!!!
What an intense journey this has been! Thanks for sharing it. If that board never fried, we wouldn't have had such an in-depth knowledge of the intricacies of Noodle Logic.
Maybe you should take it easy for your next project, and do something simpler like, you know, landing a man on the moon =p
Marc builds chip " tester/display" just to show us how it works and confirm his theory. Seen only for a minute in the video, and yet it looks like something it would take me months to work out and build and yet you know he did it in one day,,, absolute legend... smh
Congrats!
I have an old logic trainer which is considerably bigger than that one, but I don't know if it's fully working or not and it has no brand on it either so I don't know who made it. It has enough switches and LEDs on it to control an 8-bit microprocessor plugged into the breadboard.
Cool! I wish mine had more switches and LEDs, that’s why I have added a few...
It would be a nice project to replicate the 3242: Three x 74x541 for the mux, a 74x590 for the counter and some additional gates for the control signals.
Make that two 74x541, since the 74x590 already has an OE pin.
It only needed Ken to point at the screen and it was sorted immediately.