A lot of of engineers put their life into designing and constructing these machines - I really love how you bring those old "wonders" back to life. Those engineers are really unsung heroes IMHO.
The original team that designed and built this thing is on another level. I'm only barely scratching the surface of their brilliance, and even 70 years later, they're still taking me to school and teaching me all sorts of new things!
"Who on earth let me get my hands on one?!" Well, in my humble opinion, there is simply no safer place in the world for a vintage computer than in your capable hands. You deserve every inch of that piece of hardware!
It did not have the first optical tape reader, but was probably the first to use photo diodes for it. Colossus had an optical tape reader in 1943-1945. Colossus was a set of computers developed by British codebreakers in the years 1943-1945 to assist in the cryptanalysis of the Lorenz cipher.
Hi, I am often baffled by the technology in your videos but always watch, learn and enjoy! The enthusiasm that you bring is entertaining and carries me along, My wife watches with me, mainly for seeing the rabbits and cats at the end! thanks again.
Nice work on the reader; one teeny tiny 1N4007 bypassing the stinkelenium wrecktifier can really do a nice job, doesn't it? Wishing you total success on your journey. It's good to know that Bendix may have been the pioneers of photoelectric tape sensing. I see you appreciate the inconspicuous medical instruments too... Use the Forceps!
I can't help but wonder just how much of that price-tag is *labour hours* of fabrication and wiring all those backplanes. There's a lot of work in that big heavy teal beast!
I would say a considerable bit! My guess is that it's about half and half labor/R&D recoup and materials cost. But even then, $250k equivalent materials cost is pretty impressive!
In the mid 70s I used an HP "mini" that had an optical tape reader. It was designed to "NOT' transfer the tape to a 2nd reel but to just dump it on he floor. Amazingly, it wound up with no problems every time!
Thanks for showing us the next step of this journey! I loved the comment directed at those who want to replace the capacitors at all costs! I'm with you on this, it shouldn't be a routine task!
Well, you are correct in that the banded end of a diode is "more negative" when the diode is conducting. But in both the selenium and silicon diodes the markings are on the "cathode" end. In quotes as they have no actual cathode.
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode. Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
Not just old rectifiers! Modern bridge rectifier packages are often marked with "AC" or "~" for the legs that connect to the transformer, and "+" and "-" for the DC outputs.
I would check the ESR and leakage on the capacitors for one. If they are the paper-wax type I would replace them for sure. I would also make sure they are not shorted.
Wow, you have a collection of round-tuit's at 8:19. Now you have these, there is no reason to say "when I get a round toit" and many of those jobs that have been waiting can now finally be done :-)
Back in the day, there was a hack you could do to use an OC71 germanium transistor as a phototransistor, which involved scraping the black paint from the right part of the glass encapsulation to expose the junction to light.
Particularly on a part of the machine that is mechanical so will have some inherent vibration. Plus the machine needs to get transported back when it's working again. Definitely should be insulated IMO.
#PUSHTHEGREENBUTTON! The suspense is killing me! I don't know how but I have been sucked into your videos and the way you explain everything is very good. I like videos that don't hide all the troubles they had getting to the point they are at.
I might investigate replacing the vinyl tubing on those rectifiers. Such flexible PVC has plasticizers in it, and as it leaches out some of them can be rather bad for other stuff in the area.
Very happy to see that you replaced the Selenium Rectifiers with the 1N4007 diodes! I do have a question about that though. I noticed that on the top one that you did first, you have the CATHODE of the 1N4007 attached to the "+" of the selenium rectifier. Is that correct? I thought you would put the anode of the 1N4007 to the same place as the anode of the Selenium rectifier. Another thing, I strongly urge you to replace those 0.1 µF with SAFETY capacitors! (The ones where the AC power enters the unit)
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode. Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
Was about to mention that! Edit: someone mentioned that and Usagi answered, the selenium diodes have the + markings on the cathode end of the component, he linked a datasheet too.
As the selenium rectifiers have a voltage drop of several volts you could also have let them in circuit, they wouldn't get any current with the 1N4007 in parallel. Those dangling cables give me the creeps xD
I'd love to see a breakdown of that paper tape, like how many holes, speed, how it loads that onto the ram disk, you know clocking and all that. I'm really enjoying this series BTW.
there's a really easy way to see when a machine is made: when the wires are knotted together you can be pretty sure it's pre space age tech, since zip-ties were invented during this era so everything before was beautifully tied together with special wax-wire
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode. Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
08:45 Ha! I totally misidentified those components. I looked and said to myself, "Those aren't capacitors. They're clearly 93A6 diodes in 66Y2-029 yellow vinyl tubing." But of course I was wrong; they're in _66C2-029 clear_ vinyl tubing!
I had never heard of selenium rectifiers before so I looked into them. Apparently the horrible smelling gas they emit when they die is also spectacularly toxic. It's got an NFPA health hazard rating of 4. I think the silicon diodes were a good call.
yep, although a lot say they should be replaced on sight as can fail disastrously with a horrid stink, as long as not overloaded and run reasonably cool, too much heat is a big killer for them, they'll likely be ok , but i'd advise fitting a fuse in its feed, if it doesnt have one or a mains input fuse
@@andygozzo72 Over here in the UK the mains plugs have fuses in them, and the motor has a fan fitted with vents right under it. So It's prety well catered for. But yeah, I've heard you can never get rid of the smell. LOL
@@frankowalker4662 i'm in the uk, you cant rely on say a 3 amp plug fuse popping if you get a direct ht short, it wont, it'll explode the rectifier, i very strongly advise fitting a fuse in the feed the rectifier and/or a more suitable current rated fuse on the mains input, 0.315 to 0.5amp, antisurge should be about right, what make/model tape recorder?
@@andygozzo72 It's a Grundig, not sure of the model number. I gave it a recap and replaced some resistors that were out of spec. I kept checking it with my thermal imaging camera and it barely rose above room temp.
When I was exposed to this in high school, they ran a program that played Tic-Tac-Toe on the typewriter. I hope you can find that somewhere. It would be fun to see it happen again.
One thing regarding the RF decoupling filter, those old style capacitors in that unit can fail short and make the chassis live. Might be worth a look. As always a great video.
19:30 Consider 3D printing it out of flexible filament like Ninjaflex. I have repaired a vintage mechanical calculator with a 3D printed belt and it worked great!
OCD requests: please make a label to cover that ridiculous tape path drawing someone made on one of the sides of the punch mechanism (I mean, a label with the tape path properly rendered)...and please use heat shrink tubing over the tips of the cables you disconnected from the board when overriding the selenium rectifiers. Sorry for being paranoid and thanks in advance.
The typewriter looks like a Friden Flexowriter. In the 1960's I used one which was the main control device (apart from the control panel) on an Elliott 803.
Indeed: My parents built the three bedroom split level house that I and my siblings grew up in and paid $26,000 for it in 1960. ~$50k would have bought a lot of house in those days.
personally i'd say those selenuim diodes wouldnt need replacing, going by the rating of those series resistors, theres not that much current passing in them, theyre more likely to fail under ac power rectification use during the reverse part of the cycle..
if you really must replace them , try to track down some early 'top hat' silicon diodes from the early 60s like BY100, BY105, etc. or whatever equivalents you had over there! as they wouldve likely been used as service replacements back in the day ...
@usagi Electric The code cracking COLOSSUS computer that was built in WWII used an optical tape reader too. From the wiki "A tape transport with an 8-photocell reading mechanism."
Hi I'm very curious how you do that form fitting highlight line under the circuit. It's sort of becomes a halo around the diodes and such which perplexes me. Without this mystery being solved I fear I will never sleep again 😮
The voltage drop on the selenium rectifier is about 7 volts, quite a bit more than the 1.1V max drop (.6 typical) of the 1N4007. I don't know if that is going to matter or not, but it might. Thyratrons are vacuum tube versions of a SCR. Once they switch on, they continue to conduct until the voltage drops below a threshold voltage. The lower voltage drop may alter when they switch off.
David, the next time you come to NJ for VCF East you should try to get into the Bell Labs facility in Murray Hill. Nokia Bell Labs is building a new home in New Brunswick, NJ and there is no telling what will happen in the original place where transistors and Unix were created.
If you Translate Selenium-Rectifier into German They are called: Selen-Gleichrichter. Folks used to pronounce them "gleich riecht er." = 'Soon he'll smell' because of the typical smell.
A little history on why the cathode of selenium rectifiers is marked with a plus or a red dot... At the time, there was no thought of absolute current flow as it relates to identifying the terminals for anode and cathode. The terminal with the + designation was simply a way to show which side of the rectifier produced a positive DC output in a conventional rectifier circuit. In actuality, the schematic symbol for a diode is wrong today, the vertical line is meant to denote a plus sign in conjunction with the horizontal line. And, indeed, the arrow is facing the wrong direction as absolute current flow flows in the opposite direction. Likewise, all the arrows in transistors are wrong. Electrons actually flow in the opposite direction of the arrows. That's how it started, and that's how it will remain.
That's because Titanium comes after Thallium alphabetically and I accidentally pulled the wrong page from the PDF in. In my sleep deprived fog of editing, I totally didn't even realize until it was pointed out to me. Whoops!
So many thoughtfully slotted screw holes on the access panels so you don't have to lose a bunch of fiddly little hardware, and you disrespect the designers by removing them completely anyway. A field technician weeps!
That was because I was removing the panels and not going to replace them for quite a while. So, I wanted the screws completely out of the way so I wouldn't snag a cleaning rag or cloth on them as I was wiping the system down. I know it seems like I was being a bit ham-fisted, but there was a method to the madness!
The reader is full of selenium rectifiers which if get shorted smell like rotten eggs. Also they tend to have a significant voltage drop as they age. You may end up having to change them out with modern SI diodes
Selenium recitifiers can take a lot of abuse. They won't be smelly just willy-nilly. I'm not sure why they had to be replaced. They have adifferent voltage drop from the 1N4007, this may or may not be important in this circuit.
Therapeutic cleaning? One remark though regarding the reduced voltage drop over the new diodes. This impacts the anode current and so the stress on the puncher coils. Perhaps increase the anode resistor to limit the current?
What about colossus? Although it used photocells not photodiodes, it read punch tape optically at 40 ft/s or 27mph The system was clocked by the sprocket track on the tape, so there as o synchronisation of the tape to processing needed.
It would be nice to test what components you can, capacitors, resistors, diodes, or whatnot. However, understandable if you don't want to risk unsoldering things without a reasonable suspicion that they may be bad.
Ya know what... One of my motorcycles uses those selenium rectifiers and it's not charging. I'm going to try replacing the old pack out and putting them there diodes in. I'll let you know if I burn it up or not.
What happened to the microphone? It sounds weird compared to the previous videos, like it's been (partially?) liquid damaged with everthing in the lower frequency spectrum sounding somewhat nasal and distorted. Also for some reason it's now stereo (unlike prior videos), which makes the difference even more obvious (at least using headphones) since that distortion is mostly on the left but will move towards the center when he moves around, especially during the first 5 mins or so 🤨 Strong example at 3:00 where he moves his head and points towards the machine, and the sound (including the distorted nasal sounding mid-range frequencies) move to the left (which also means the mic is the wrong way around, or it's always been like this but because the microphone track was mono, we didn't notice)
I am struggling to understand what the purpose of the selenium rectifiers is. How can the anode voltage ever be higher than the solenoid voltage and turn off the rectifier? Is there something else connected to the PLF16 connectors that can pull the solenoid low?
Are you sure that those diodes aren't Germanium, instead of Silicon? I worked at a U.K. factory where Germanium diodes had been made a few decades earlier. In their history display they had a number of Germanium diodes which looked pretty much identical to the components in that equipment.
I can't quite understand the placement of the tape punch behind the reader. I guess that it had to have a reel of fresh tape and produced punched tape which needed to be removed, none of which are accessible without opening the side panels. Or am I missing something? By the way, I used a flexowriter in my first job for running a mail merge. One tape loop had the letter itself and the other the names and addresses. I was quite impressed by all this in 1974. And almost deafened!
Odd that the negative side of the selenium rectifier is labeled positive. At first I thought you had the 1N4000 series diodes in the wrong way. Does that TEAC work? I've got a A-4010 SL and a 4010 GSL, nice machines and about 20 others including 2 all vacuum tube machines from 1959 and 60. A little advice on bearings, open bearings may have been meant to run dry as they will not collect and hold dust.
That's because Titanium comes after Thallium alphabetically and I accidentally pulled the wrong page from the PDF in. In my sleep deprived fog of editing, I totally didn't even realize until it was pointed out to me. Whoops!
Generally speaking, a selenium diode can be strapped with a modern diode, assuming it's not shorted. A modern diode like a 1N4007 has a much lower resistance, so the selenium will simply be ignored thanks to Ohm's Law. However, it's still best to disconnect one or both legs for long-term safety. Seleniums are unstable over time whether there's current applied or not, so imagine the carnage if the silicon diode decided to open up, or if the selenium decided to short out due to it physically aging. Not worth the gamble in the end!
Those old capacitors/components a lot of the time if you energize them gently or heck even full send sometimes they will come around if they have not started leaking and if not capacitors will possibly burn up indicating issue and how those are built likely will not damage anything critical if they do go nuclear. If they work and are in spec and are not leaking and don't fry I see no reason to replace them. I think you are making the right call, though bear in mind I have not watched past 9:11 yet so something could happen but in my experience it will likely be just fine. I would just recommend keeping an eye on them during routine service intervals and replace them AS NEEDED, not just because. Those are vintage components and are part of the originality of the part/product. Why ruin that originality if it's not necessary? =)
Yes an ESR will be a good investment to check the caps. And if those are indeed electronic will be good to reform them or just bring them back to life slowly with a bench power supply.
A lot of of engineers put their life into designing and constructing these machines - I really love how you bring those old "wonders" back to life.
Those engineers are really unsung heroes IMHO.
Think also about the people who assembled these machines. Strung all that wire. So very tedious. They were artists.
The original team that designed and built this thing is on another level. I'm only barely scratching the surface of their brilliance, and even 70 years later, they're still taking me to school and teaching me all sorts of new things!
"Who on earth let me get my hands on one?!" Well, in my humble opinion, there is simply no safer place in the world for a vintage computer than in your capable hands. You deserve every inch of that piece of hardware!
Thank you so much!
Hopefully it all comes up smoothly and we can get this beast back up to System Source and let museum-goers get hands on with it!
@@UsagiElectric💯 agree
And we'll happily be along for the ride, with a fresh batch of popcorn at the ready. :D Best of luck! @@UsagiElectric
It did not have the first optical tape reader, but was probably the first to use photo diodes for it.
Colossus had an optical tape reader in 1943-1945. Colossus was a set of computers developed by British codebreakers in the years 1943-1945 to assist in the cryptanalysis of the Lorenz cipher.
Good catch! The Colossus was pretty epic in what it was capable of at the time!
@@UsagiElectric Charles Forbin never should have built it.
Hi, I am often baffled by the technology in your videos but always watch, learn and enjoy! The enthusiasm that you bring is entertaining and carries me along, My wife watches with me, mainly for seeing the rabbits and cats at the end! thanks again.
Is there a rabbit channel for her to watch?
Nice work on the reader; one teeny tiny 1N4007 bypassing the stinkelenium wrecktifier can really do a nice job, doesn't it? Wishing you total success on your journey. It's good to know that Bendix may have been the pioneers of photoelectric tape sensing.
I see you appreciate the inconspicuous medical instruments too... Use the Forceps!
I can't help but wonder just how much of that price-tag is *labour hours* of fabrication and wiring all those backplanes. There's a lot of work in that big heavy teal beast!
I would say a considerable bit! My guess is that it's about half and half labor/R&D recoup and materials cost. But even then, $250k equivalent materials cost is pretty impressive!
i love the fact it needs a hopper to collect all the punched holes
It's only a matter of time before you get a Cray. Calling it.
X-1 or X-MP? Or both?
In the mid 70s I used an HP "mini" that had an optical tape reader. It was designed to "NOT' transfer the tape to a 2nd reel but to just dump it on he floor. Amazingly, it wound up with no problems every time!
I've had the dubious pleasure of smelling a burned-up Se rectifier. It was pretty unpleasant but not enough to drive me from the room.
Love your channel. Love this project.
1958 computing never looked so possible.
I am amazed that you can find schematic diagrams that are from so long ago. That is some awesome research skills.
Wrote my first program on a G15D Pomona College 1958
Thanks for showing us the next step of this journey! I loved the comment directed at those who want to replace the capacitors at all costs! I'm with you on this, it shouldn't be a routine task!
Nice work! I suggest putting heat-shrink on those free-hanging rectifier wires, in case they end up touching anything nearby.
Did you solder the diodes the right way round?
Where the plus sign is on the Selenium diode you have soldered the negative pole of the diode.
Well, you are correct in that the banded end of a diode is "more negative" when the diode is conducting. But in both the selenium and silicon diodes the markings are on the "cathode" end. In quotes as they have no actual cathode.
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode.
Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
@@UsagiElectric yep, the + sign on old rectifiers usually indicates the output polarity
Not just old rectifiers! Modern bridge rectifier packages are often marked with "AC" or "~" for the legs that connect to the transformer, and "+" and "-" for the DC outputs.
I was thinking the same. Good thing I read through the comments before posting 😅
Awesome work, looking forward to engaging DC!
I would check the ESR and leakage on the capacitors for one. If they are the paper-wax type I would replace them for sure. I would also make sure they are not shorted.
Wow, you have a collection of round-tuit's at 8:19. Now you have these, there is no reason to say "when I get a round toit" and many of those jobs that have been waiting can now finally be done :-)
Back in the day, there was a hack you could do to use an OC71 germanium transistor as a phototransistor, which involved scraping the black paint from the right part of the glass encapsulation to expose the junction to light.
I don't know, it's that "wire twisted safely out of the way" safe enough? It looks so near the leg of the new diode...
Particularly on a part of the machine that is mechanical so will have some inherent vibration. Plus the machine needs to get transported back when it's working again. Definitely should be insulated IMO.
#PUSHTHEGREENBUTTON! The suspense is killing me! I don't know how but I have been sucked into your videos and the way you explain everything is very good. I like videos that don't hide all the troubles they had getting to the point they are at.
I might investigate replacing the vinyl tubing on those rectifiers. Such flexible PVC has plasticizers in it, and as it leaches out some of them can be rather bad for other stuff in the area.
Very happy to see that you replaced the Selenium Rectifiers with the 1N4007 diodes! I do have a question about that though. I noticed that on the top one that you did first, you have the CATHODE of the 1N4007 attached to the "+" of the selenium rectifier. Is that correct? I thought you would put the anode of the 1N4007 to the same place as the anode of the Selenium rectifier.
Another thing, I strongly urge you to replace those 0.1 µF with SAFETY capacitors! (The ones where the AC power enters the unit)
Just checking the comments before commenting, "Are you sure the 1N4007s are attached correctly?"
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode.
Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
@@UsagiElectric Correct! The + mark on an old selenium is the banded end of a modern diode.
wow, that is an important point for me to remember @@UsagiElectric
it would be worth specifically calling that out in video, so those of us who dont know better put a diode in backwards someday @@UsagiElectric
Love the cotton tails. Ohh really like circuit sim use too. But then cotton tails. That's epic !
If it is bendix that drive belt is probably stock from a washing machine
Looking forward to the big switch on. It's a great series to watch.
I'm worried that you've put the new diodes around the wrong way. Hopefully everything is all good there. All the best, and I love your work.
Was about to mention that!
Edit: someone mentioned that and Usagi answered, the selenium diodes have the + markings on the cathode end of the component, he linked a datasheet too.
Such a neat project but I have to admit: I'm super happy the bunnies are doing OK!
So you didn't add a dropping resistor to the 1N4007? Remember, that old rectifier has a more dropping voltage compare to the 1N4007/.
As the selenium rectifiers have a voltage drop of several volts you could also have let them in circuit, they wouldn't get any current with the 1N4007 in parallel.
Those dangling cables give me the creeps xD
Your movies are like a long and everlasting journey and you let us be part of it. Thank you :-)
Selenium rectifiers are just about the coolest looking components ever.
theyre still made for certain applications ,
@@andygozzo72 wow like what applications?
@@supercompooper battery charging mainly, as their higher internal resistance helps to limit and partially regulate current
I'd love to see a breakdown of that paper tape, like how many holes, speed, how it loads that onto the ram disk, you know clocking and all that. I'm really enjoying this series BTW.
22:07 Nice job! Though you might want to slip some heat shrink over the dangly wires remaining exposed.
there's a really easy way to see when a machine is made: when the wires are knotted together you can be pretty sure it's pre space age tech, since zip-ties were invented during this era so everything before was beautifully tied together with special wax-wire
2024 is the year of the Bendix!
I'm loving this project so far and I can't wait for the next episode!
Why have you connected the new diode cathode to the anode (+ sign>) of the selenium rectifiers? Aren't they the wrong way around?
In both the selenium and silicon diodes the markings are on the "cathode" end. In quotes as they have no actual cathode.
I double/triple checked the diodes were installed correctly according to the Federal datasheet on those specific selenium rectifiers. For whatever reason, the "+" mark on the selenium rectifiers is equivalent to the bar on the diode.
Check out the Federal datasheets here: www.worldradiohistory.com/BOOKSHELF-ARH/Technology/Federal-Selenium-Rectifier-2nd-1953.pdf
Execellent and glad I'm wrong for a change!
@@UsagiElectric
Interesting to realize that time, the tape reader was state-of-the-art futuristic technology. I can imagine the engineer bragging about it.
Can't wait to see some program running on this beast! That would be so epic!
08:45 Ha! I totally misidentified those components. I looked and said to myself, "Those aren't capacitors. They're clearly 93A6 diodes in 66Y2-029 yellow vinyl tubing." But of course I was wrong; they're in _66C2-029 clear_ vinyl tubing!
I had never heard of selenium rectifiers before so I looked into them. Apparently the horrible smelling gas they emit when they die is also spectacularly toxic. It's got an NFPA health hazard rating of 4. I think the silicon diodes were a good call.
I’ve been exposed to a few thick clouds of selenium rectifier smoke and it hasn’t hurt me one bit.
I bought a reel to reel recorder last year that had a selenium rectifier dated 1957, and it still works perfectly. They are pretty robust.
yep, although a lot say they should be replaced on sight as can fail disastrously with a horrid stink, as long as not overloaded and run reasonably cool, too much heat is a big killer for them, they'll likely be ok , but i'd advise fitting a fuse in its feed, if it doesnt have one or a mains input fuse
@@andygozzo72 Over here in the UK the mains plugs have fuses in them, and the motor has a fan fitted with vents right under it. So It's prety well catered for. But yeah, I've heard you can never get rid of the smell. LOL
@@frankowalker4662 i'm in the uk, you cant rely on say a 3 amp plug fuse popping if you get a direct ht short, it wont, it'll explode the rectifier, i very strongly advise fitting a fuse in the feed the rectifier and/or a more suitable current rated fuse on the mains input, 0.315 to 0.5amp, antisurge should be about right, what make/model tape recorder?
@@andygozzo72 It's a Grundig, not sure of the model number. I gave it a recap and replaced some resistors that were out of spec. I kept checking it with my thermal imaging camera and it barely rose above room temp.
@@frankowalker4662 grundigs usually had internal fuses anyway i have a TK20, used to have a couple of others but sold them some years back
When I was exposed to this in high school, they ran a program that played Tic-Tac-Toe on the typewriter. I hope you can find that somewhere. It would be fun to see it happen again.
One thing regarding the RF decoupling filter, those old style capacitors in that unit can fail short and make the chassis live. Might be worth a look.
As always a great video.
19:30 Consider 3D printing it out of flexible filament like Ninjaflex. I have repaired a vintage mechanical calculator with a 3D printed belt and it worked great!
OCD requests: please make a label to cover that ridiculous tape path drawing someone made on one of the sides of the punch mechanism (I mean, a label with the tape path properly rendered)...and please use heat shrink tubing over the tips of the cables you disconnected from the board when overriding the selenium rectifiers. Sorry for being paranoid and thanks in advance.
The typewriter looks like a Friden Flexowriter. In the 1960's I used one which was the main control device (apart from the control panel) on an Elliott 803.
$49500 for the basic computer! I think, this was the price for a luxury house in the US in the 1950s.
Indeed: My parents built the three bedroom split level house that I and my siblings grew up in and paid $26,000 for it in 1960. ~$50k would have bought a lot of house in those days.
personally i'd say those selenuim diodes wouldnt need replacing, going by the rating of those series resistors, theres not that much current passing in them, theyre more likely to fail under ac power rectification use during the reverse part of the cycle..
if you really must replace them , try to track down some early 'top hat' silicon diodes from the early 60s like BY100, BY105, etc. or whatever equivalents you had over there! as they wouldve likely been used as service replacements back in the day ...
@usagi Electric The code cracking COLOSSUS computer that was built in WWII used an optical tape reader too. From the wiki "A tape transport with an 8-photocell reading mechanism."
Hi I'm very curious how you do that form fitting highlight line under the circuit. It's sort of becomes a halo around the diodes and such which perplexes me. Without this mystery being solved I fear I will never sleep again 😮
Do you mean the color coded highlighting that I show on schematics?
I draw it all by hand in Krita, the image editing program I use!
@@UsagiElectric that's amazing. How does it sort of take the profile of the shapes like diodes and stuff?
i assume the trick is just selecting the relevant parts by colour (the "magic wand" tool), then doing a "grow selection" on that
Can't wait for DC!
"Thyrotron".... tube version of an SCR. :)
its very cool just to see this stuff, and how it was constructed!
The voltage drop on the selenium rectifier is about 7 volts, quite a bit more than the 1.1V max drop (.6 typical) of the 1N4007. I don't know if that is going to matter or not, but it might. Thyratrons are vacuum tube versions of a SCR. Once they switch on, they continue to conduct until the voltage drops below a threshold voltage. The lower voltage drop may alter when they switch off.
David, the next time you come to NJ for VCF East you should try to get into the Bell Labs facility in Murray Hill. Nokia Bell Labs is building a new home in New Brunswick, NJ and there is no telling what will happen in the original place where transistors and Unix were created.
Totally agree!! Only change a component when it’s failed otherwise your are just creating waste
That motor had more slop than a pig on a farm.
If you Translate Selenium-Rectifier into German They are called: Selen-Gleichrichter. Folks used to pronounce them "gleich riecht er." = 'Soon he'll smell' because of the typical smell.
Will be cool to see those capacitors releasing the magic smoke 😁😁
The best computing museum in the world is in Bletchley in the UK
A little history on why the cathode of selenium rectifiers is marked with a plus or a red dot... At the time, there was no thought of absolute current flow as it relates to identifying the terminals for anode and cathode. The terminal with the + designation was simply a way to show which side of the rectifier produced a positive DC output in a conventional rectifier circuit. In actuality, the schematic symbol for a diode is wrong today, the vertical line is meant to denote a plus sign in conjunction with the horizontal line. And, indeed, the arrow is facing the wrong direction as absolute current flow flows in the opposite direction. Likewise, all the arrows in transistors are wrong. Electrons actually flow in the opposite direction of the arrows. That's how it started, and that's how it will remain.
Just FYI... that dollars per pound list you put in the video @4:40 was for thallium, not titanium.
That's because Titanium comes after Thallium alphabetically and I accidentally pulled the wrong page from the PDF in. In my sleep deprived fog of editing, I totally didn't even realize until it was pointed out to me. Whoops!
@@UsagiElectricHEH no prob, just figured you'd wanna know!
So many thoughtfully slotted screw holes on the access panels so you don't have to lose a bunch of fiddly little hardware, and you disrespect the designers by removing them completely anyway. A field technician weeps!
I saw the same thing and cannot unsee it 😂.
I concur.
That was because I was removing the panels and not going to replace them for quite a while. So, I wanted the screws completely out of the way so I wouldn't snag a cleaning rag or cloth on them as I was wiping the system down.
I know it seems like I was being a bit ham-fisted, but there was a method to the madness!
@@UsagiElectric All in good fun anyhow. 😄 You've been nothing but meticulous on this project, and it continues to be absolutely amazing!
The PDP-12 might just be the most beautiful computer ever. Perhaps tied with the PDP-15.
Old computers deserve a second chance.
Because of history.
So that we can tell our children where it all started.
Stunning project!
The reader is full of selenium rectifiers which if get shorted smell like rotten eggs. Also they tend to have a significant voltage drop as they age. You may end up having to change them out with modern SI diodes
Selenium recitifiers can take a lot of abuse. They won't be smelly just willy-nilly. I'm not sure why they had to be replaced. They have adifferent voltage drop from the 1N4007, this may or may not be important in this circuit.
Therapeutic cleaning?
One remark though regarding the reduced voltage drop over the new diodes.
This impacts the anode current and so the stress on the puncher coils.
Perhaps increase the anode resistor to limit the current?
What was the problem with the loose motor ? was it just loose screws or was something broken ?
I'd love to see some emulated hardware running something with similar speed of the g15
Actually the LGP30 uses a modified Flexowriter as a terminal.
Good call bypassing those selenium diodes. When they go, they release their ghost and that ghost is really foul smelling one.
What about colossus?
Although it used photocells not photodiodes, it read punch tape optically at 40 ft/s or 27mph
The system was clocked by the sprocket track on the tape, so there as o synchronisation of the tape to processing needed.
It would be nice to test what components you can, capacitors, resistors, diodes, or whatnot. However, understandable if you don't want to risk unsoldering things without a reasonable suspicion that they may be bad.
Ya know what...
One of my motorcycles uses those selenium rectifiers and it's not charging.
I'm going to try replacing the old pack out and putting them there diodes in.
I'll let you know if I burn it up or not.
Imagine this thing converted into a modern server cabinet! (If it was completely borked)
Since it's used to lay down signals on the drum, is the tape reader somehow controlled to run in time with the read only clock signal on the drum?
What happened to the microphone? It sounds weird compared to the previous videos, like it's been (partially?) liquid damaged with everthing in the lower frequency spectrum sounding somewhat nasal and distorted. Also for some reason it's now stereo (unlike prior videos), which makes the difference even more obvious (at least using headphones) since that distortion is mostly on the left but will move towards the center when he moves around, especially during the first 5 mins or so 🤨 Strong example at 3:00 where he moves his head and points towards the machine, and the sound (including the distorted nasal sounding mid-range frequencies) move to the left (which also means the mic is the wrong way around, or it's always been like this but because the microphone track was mono, we didn't notice)
Is the new Diode on reverse? Seems the Cathode is connected on the “+” of the Selenium Rectifiers
On the selenium diode and I see the cathode of the 1N4007 connect to the + terminal of the selenium. That seems odd.
the little bunnies looking good
I am struggling to understand what the purpose of the selenium rectifiers is. How can the anode voltage ever be higher than the solenoid voltage and turn off the rectifier? Is there something else connected to the PLF16 connectors that can pull the solenoid low?
Are you sure that those diodes aren't Germanium, instead of Silicon? I worked at a U.K. factory where Germanium diodes had been made a few decades earlier. In their history display they had a number of Germanium diodes which looked pretty much identical to the components in that equipment.
I can't quite understand the placement of the tape punch behind the reader. I guess that it had to have a reel of fresh tape and produced punched tape which needed to be removed, none of which are accessible without opening the side panels. Or am I missing something?
By the way, I used a flexowriter in my first job for running a mail merge. One tape loop had the letter itself and the other the names and addresses. I was quite impressed by all this in 1974. And almost deafened!
I think in one of the first videos, he showed the tape punch on the back of the machine??? I'm not sure though.
4:39 did you accidentally drag the thallium chart instead of the titanium one?
so is that Paper tape or like what larger computers used with tape with Iron oxide on it?
9:42 :- 0.1μF seems awfully small for an electrolytic capacitor
most likely paper in oil.
Odd that the negative side of the selenium rectifier is labeled positive. At first I thought you had the 1N4000 series diodes in the wrong way. Does that TEAC work? I've got a A-4010 SL and a 4010 GSL, nice machines and about 20 others including 2 all vacuum tube machines from 1959 and 60. A little advice on bearings, open bearings may have been meant to run dry as they will not collect and hold dust.
04:39 price for pound of Thallium not for Titanium :(
That's because Titanium comes after Thallium alphabetically and I accidentally pulled the wrong page from the PDF in. In my sleep deprived fog of editing, I totally didn't even realize until it was pointed out to me. Whoops!
Generally speaking, a selenium diode can be strapped with a modern diode, assuming it's not shorted. A modern diode like a 1N4007 has a much lower resistance, so the selenium will simply be ignored thanks to Ohm's Law. However, it's still best to disconnect one or both legs for long-term safety. Seleniums are unstable over time whether there's current applied or not, so imagine the carnage if the silicon diode decided to open up, or if the selenium decided to short out due to it physically aging. Not worth the gamble in the end!
Those old capacitors/components a lot of the time if you energize them gently or heck even full send sometimes they will come around if they have not started leaking and if not capacitors will possibly burn up indicating issue and how those are built likely will not damage anything critical if they do go nuclear. If they work and are in spec and are not leaking and don't fry I see no reason to replace them. I think you are making the right call, though bear in mind I have not watched past 9:11 yet so something could happen but in my experience it will likely be just fine. I would just recommend keeping an eye on them during routine service intervals and replace them AS NEEDED, not just because. Those are vintage components and are part of the originality of the part/product. Why ruin that originality if it's not necessary? =)
What is the problem with selenium rectifiers?
Do you have an ESR meter to quickly check those caps in circuit?
Yes an ESR will be a good investment to check the caps. And if those are indeed electronic will be good to reform them or just bring them back to life slowly with a bench power supply.
Thump for the bunnies!
(Your story was also interesting)
Did Boeing do the pt reader/punch?
Why change selenium diodes right away? Have you checked them? Perhaps they are fine. These are reliable components
Where in the world do you find paper punch tape???