Hi there! In 1943 the Colossus computers used to aid decryption of the Lorenz cipher at Bletchley Park used photoelectric tape readers. They could read 5 hole tape at 5000 characters per second, with the tape moving at 30 mph. The tape was advanced by pinch wheels rather than driving it with the sprocket holes to avoid tearing the tape. The sprocket holes were also read by photoelectric detectors and was used to clock the whole machine so its operation was completely synchronous with incoming data.
@xplora1a
7 ай бұрын
en.wikipedia.org/wiki/Colossus_computer
@Quizidomo
7 ай бұрын
When they ran the tape at 60 mph it disintegrated so they had to slow it down to 30 mph. Colossus had no trouble reading the tape at 60mph though. It is estimated that it could have processed 10,000 cps with ease.
@val82791
7 ай бұрын
Not just computers: "After amplification, the sound from the microphone was fed to an electromagnet that vibrated a pen with black ink, under which a paper ribbon was stretched. After that, the tape was passed through a photocell, directing light from a powerful lamp onto the paper. The recorded vibrations caused voltage changes at the output of the photocell, were amplified and fed to the loudspeaker, which reproduced the recorded." kzitem.info/news/bejne/2IN40pVmgZd_p34
@UsagiElectric
7 ай бұрын
Thank you for the insight! Interestingly, the Colossus uses vacuum photocells, which are quite a bit different than photodiodes. I think we may have two firsts here: the Colossus is the first for an optical tape reader, and the G15 is the first to use photodiodes for an optical tape reader!
@tiepup
7 ай бұрын
As with most things at Bletchley Park we didn't know about them until relatively recently because of all the governmental secrets. At least Tommy Flowers is now starting to get some recognition for his amazing contribution to computing.
@magnusnordlund3787
7 ай бұрын
"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!
@UsagiElectric
7 ай бұрын
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!
@numlockkilla
7 ай бұрын
@@UsagiElectric💯 agree
@magnusnordlund3787
7 ай бұрын
And we'll happily be along for the ride, with a fresh batch of popcorn at the ready. :D Best of luck! @@UsagiElectric
@carstenfrandsen
7 ай бұрын
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.
@KameraShy
7 ай бұрын
Think also about the people who assembled these machines. Strung all that wire. So very tedious. They were artists.
@UsagiElectric
7 ай бұрын
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!
@headpox5817
7 ай бұрын
Australia's first computer, CSIRAC, built in 1949 was fitted (around 1951) with a 12-hole optical paper tape reader using photodiodes.
@UsagiElectric
7 ай бұрын
Oooh, excellent catch! That's a machine I know almost nothing about, but that's awesome!
@Photo_CB
6 ай бұрын
@@UsagiElectricand the Elliott 402 of 1955 had an optical five-hole tape reader. Heck, even Collossus code-cracking machine from 1943 read its input tapes optically.
@egelmuis
7 ай бұрын
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.
@UsagiElectric
7 ай бұрын
Good catch! The Colossus was pretty epic in what it was capable of at the time!
@gushiperson
7 ай бұрын
@@UsagiElectric Charles Forbin never should have built it.
@StevesRetroFunzzz
2 ай бұрын
""it needs to be cleaned, and all the spinning bits oiled" - quote of the week!!
@andygozzo72
7 ай бұрын
some early mullard phototdiodes/phototransistors were actually how some early glass encased germanium transistors started off, if they were found to have good light response, they were encapsulated as photocells, if poor, they became a OC70 or OC71 transistor, clear silicone gel for light use, white opaque for transistor, although you can find some transistors with clear silicone gel if you scrape the black paint off
@theantipope4354
7 ай бұрын
Ha! I'm glad I'm not the one who remembers that trick! Wow, that's going back a very long time.
@NiallWardrop
7 ай бұрын
I remember somewhat later cutting the top off a salvaged BC108 with a razor saw to make an NPN phototransistor, because proper phototransistors were expensive and not generally found on scrap / surplus boards. A drop of clear resin or similar was recommended for protection.
@TomFynn
7 ай бұрын
You should nickname the reader "Judy", so you could have your own Punch and Judy show.
@pete3897
7 ай бұрын
When my friends daughter Judy got the first bicycle that she didn't have to share with her brother it got an utter thrashing. It was 100% Judy cycle.
@UsagiElectric
7 ай бұрын
Hehe, I'll forever think of Punch and Judy every time I look at the paper tape punch.
@ChristianPinnock-u5c
7 ай бұрын
🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣
@douro20
7 ай бұрын
The 2D21 was a very popular tube, somewhat similar electrically to the 2050. It was extensively used in computers, primarily in reader and punch applications. The 5727 is a special version, ruggedized and subjected to 500-hour batch tests to ensure its reliability and precise operating characteristics. You will also find them in electronic metronomes, namely later versions of the Crystalab Metronoma and a number of those produced by Seth Thomas.
@neilmusgrove4668
7 ай бұрын
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.
@KameraShy
7 ай бұрын
Is there a rabbit channel for her to watch?
@Mariano.Bernacki
7 ай бұрын
It's only a matter of time before you get a Cray. Calling it.
@minty_Joe
6 ай бұрын
X-1 or X-MP? Or both?
@GilmerJohn
6 ай бұрын
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!
@jeromethiel4323
7 ай бұрын
"Hop to it," on a channel called Usagi (rabbit in Japanese) electric. I see what you did there, and i love it!
@Tgspartnership
7 ай бұрын
i love the fact it needs a hopper to collect all the punched holes
@KeritechElectronics
7 ай бұрын
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!
@NoPegs
7 ай бұрын
Colossus's paper tape reader was optical using photocells... December 1943. (The "bed-stead" was the nickname for the tape loop reader.)
@gabotron94
2 ай бұрын
But was the Bendix the first using photodiodes?
@tamberp
7 ай бұрын
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!
@UsagiElectric
7 ай бұрын
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!
@zxborg9681
7 ай бұрын
The nice thing about the 1N4007 mod is that since the forward voltage is almost an order of magnitude lower, so will the power dissapation through it. Those big chunky fins on the selenium devices were mainly there b/c their forward voltage drop was so high so they wasted tons of power. I'm enjoying your channel, your enthusiasm for old tech is contagious, and some of the machines you're showing are really amazing!
@buffler1
7 ай бұрын
Wrote my first program on a G15D Pomona College 1958
@AzagXul666
6 ай бұрын
Man, what a journey this is, can't wait for the moment when that beast of a machine comes fully alive! Cheers from Finland!
@johnopalko5223
7 ай бұрын
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.
@johngormley2192
5 ай бұрын
I am amazed that you can find schematic diagrams that are from so long ago. That is some awesome research skills.
@philipnasadowski1060
7 ай бұрын
The 2D21 was also used in the first model (V200) of Seeburg jukeboxes with the 'Tormat' selector system. Tormat was actually a magnetic core memory, in 1955 (!). They went to the 2050 with the next machines. The 2050 tube was used to trip the machine from 'scan' mode into loading a record to play. They used Tormat from 1955 to the late 70's It was a neat system, when it worked, and a bear to fix when it didn't.
@emilschw8924
6 ай бұрын
Old computers deserve a second chance. Because of history. So that we can tell our children where it all started.
@Derpy1969
7 ай бұрын
Love your channel. Love this project. 1958 computing never looked so possible.
@stphinkle
7 ай бұрын
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.
@sinebar
6 ай бұрын
When I was working as an engineer, our model shop had an old Agie wire EDM that ran off punch tape that was loaded on what resembled film reels. The way it worked was the NC program was ran through a punch machine and the resulting paper punch tape was then loaded onto the reel and the wire EDM made the part. It was all analog but very accurate. They eventually upgraded it to run off I think a Greco box so they could disperse with the punch tape which was prone to damage.
@thirstyCactus
15 күн бұрын
Nice work! I suggest putting heat-shrink on those free-hanging rectifier wires, in case they end up touching anything nearby.
@theantipope4354
7 ай бұрын
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.
@adamw.8579
7 ай бұрын
This fancy gas-filled tubes actually are called thyratrons - similar to semiconductor brothers - thyristors, acts same way. Also was used as switching devices for large currents. Selenium rectifiers are durable when are sealed, moisture can destroy it within hours. Check coating on these modules, if the paint is intact and whole computer was stored in dry place everything should be fine.
@highpath4776
7 ай бұрын
If it is bendix that drive belt is probably stock from a washing machine
@tony359
7 ай бұрын
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!
@ByGrabtharsHammer
7 ай бұрын
With all of this relay madness, the EMI filter may protect the logic of the computer from the paper tape reader, not the other way around...
@evmemc
7 ай бұрын
Awesome work, looking forward to engaging DC!
@TheEPROM9
7 ай бұрын
Colossus in WWII use for cracking the Lorense code use by the top brass of the Narsi party. Used an optical reader for the punch tape. I think it used CDS cells as diodes had not been invented at the time.
@BSDKllr
7 ай бұрын
#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.
@thomasklima215
7 ай бұрын
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
@vanhetgoor
7 ай бұрын
I still remember the smell of this kind of old electronics, the thick layers of dust inside and the oil used to smooth the rolling of axes and motors. The non-metric, kind of stainless steel, screws that could only be used there, at that specific spot and nowhere else. Massive plates of metal for the casing within another metal case. Huge connectors that were one of a kind, sometimes I think what got into their minds to produce stuff like that, so heavy, so large, so unliftable.
@timc3600
7 ай бұрын
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 :-)
@jackhack1972
7 ай бұрын
Love the cotton tails. Ohh really like circuit sim use too. But then cotton tails. That's epic !
@darkwinter7395
7 ай бұрын
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.
@lukemccreagames836
7 ай бұрын
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.
@poyuuu8061
7 ай бұрын
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.
@pjcnet
7 ай бұрын
It's amazingly small and compact considering most computers filled a room in those days, the innovation is amazing with no expense spared, this was absolute cutting edge technology even down to the optical tape reader and it was certainly built to last, it's incredible how this can be in such good condition after over 65 years, most of which it's been redundant and left to deteriorate with time. I can't wait until the day you get this processing code, still a long way to go, almost certainly with some unexpected challenges ahead, but you'll get there.
@DumahBrazorf
7 ай бұрын
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...
@cdh76
7 ай бұрын
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.
@supercompooper
7 ай бұрын
Selenium rectifiers are just about the coolest looking components ever.
@andygozzo72
7 ай бұрын
theyre still made for certain applications ,
@supercompooper
7 ай бұрын
@@andygozzo72 wow like what applications?
@andygozzo72
7 ай бұрын
@@supercompooper battery charging mainly, as their higher internal resistance helps to limit and partially regulate current
@rtfmpeople
7 ай бұрын
Such a neat project but I have to admit: I'm super happy the bunnies are doing OK!
@tubeDude48
7 ай бұрын
So you didn't add a dropping resistor to the 1N4007? Remember, that old rectifier has a more dropping voltage compare to the 1N4007/.
@dasiro
7 ай бұрын
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
@Curt_Sampson
7 ай бұрын
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!
@thefrankly
7 ай бұрын
Incredible mechanical work you do, absolutely fascinating.
@IainShepherd1
7 ай бұрын
Inspiring as ever. All your babies get the best of care including the electro-mechanical ones. (I know the Bendix isn’t “your” baby but. 😊) Absolutely gotta see System Source when I’m next in USA. No visits planned but … this decade!
@TheHylianBatman
7 ай бұрын
2024 is the year of the Bendix! I'm loving this project so far and I can't wait for the next episode!
@malcolmgibson6288
7 ай бұрын
Looking forward to the big switch on. It's a great series to watch.
@martinhow121
7 ай бұрын
That price list was for Thallium, not Titanium. A very different metal.
@UsagiElectric
7 ай бұрын
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!
@martinhow121
7 ай бұрын
@@UsagiElectric Great work , please keep it up. And you sure would not want to be handling Thallium. Its very poisonous and its use featured in some high profile murders in the UK in the early 1970 - the Bovingdon Teacup Poisoner Etc. My Chemistry teacher lived in Bovingdon so we were always careful around him!
@jensschroder8214
7 ай бұрын
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.
@georgegonzalez2476
7 ай бұрын
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.
@UsagiElectric
7 ай бұрын
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
@andygozzo72
7 ай бұрын
@@UsagiElectric yep, the + sign on old rectifiers usually indicates the output polarity
@gcewing
7 ай бұрын
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.
@Colaholiker
7 ай бұрын
I was thinking the same. Good thing I read through the comments before posting 😅
@thromboid
7 ай бұрын
Those are some beautiful schematics. Someone really cared.
@Ardamax_
7 ай бұрын
Man, this Bendix machine is so cool. Thank you for introducing me to the world of early computing. It's all so interesting.
@jurjenbos228
7 ай бұрын
Interesting to realize that time, the tape reader was state-of-the-art futuristic technology. I can imagine the engineer bragging about it.
@ronny332
7 ай бұрын
Your movies are like a long and everlasting journey and you let us be part of it. Thank you :-)
@liquidmandotcom
7 ай бұрын
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.
@andreas7136
7 ай бұрын
$49500 for the basic computer! I think, this was the price for a luxury house in the US in the 1950s.
@pscheie
7 ай бұрын
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.
@projectartichoke
7 ай бұрын
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.
@megatesla
6 ай бұрын
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!
@MinorLG
6 ай бұрын
I recently bought a kingdom kt-70PC terminal, and it just came in today. Bought manual separate, and both came in today
@jaimdiojtar
7 ай бұрын
i love the G15 series how after so many months you slowly revive this beast
@johnhelt5475
7 ай бұрын
22:07 Nice job! Though you might want to slip some heat shrink over the dangly wires remaining exposed.
@BlackHoleForge
7 ай бұрын
That motor had more slop than a pig on a farm.
@dualityk
7 ай бұрын
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!
@MarianoLu
7 ай бұрын
I saw the same thing and cannot unsee it 😂.
@ghydda
7 ай бұрын
I concur.
@UsagiElectric
7 ай бұрын
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!
@dualityk
7 ай бұрын
@@UsagiElectric All in good fun anyhow. 😄 You've been nothing but meticulous on this project, and it continues to be absolutely amazing!
@Levora
6 ай бұрын
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.
@waynethompson8416
7 ай бұрын
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)
@axelBr1
7 ай бұрын
Just checking the comments before commenting, "Are you sure the 1N4007s are attached correctly?"
@UsagiElectric
7 ай бұрын
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
@n2n8sda
7 ай бұрын
@@UsagiElectric Correct! The + mark on an old selenium is the banded end of a modern diode.
@dont-want-no-wrench
7 ай бұрын
wow, that is an important point for me to remember @@UsagiElectric
@dont-want-no-wrench
7 ай бұрын
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
@null_carrier
7 ай бұрын
That machine will run some code before it's even 70 years old.
@andygozzo72
7 ай бұрын
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..
@andygozzo72
7 ай бұрын
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 ...
@mikefochtman7164
7 ай бұрын
"Thyrotron".... tube version of an SCR. :)
@GaitaPonto
7 ай бұрын
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.
@alc5440
7 ай бұрын
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.
@georgegonzalez2476
7 ай бұрын
I’ve been exposed to a few thick clouds of selenium rectifier smoke and it hasn’t hurt me one bit.
@zaraak323i
7 ай бұрын
CR1-6 look like snubber diodes. They safely take any high voltage generated by the coils/relays to ground.
@arcadeuk
7 ай бұрын
I can't trust selenium rectifiers at all, so glad you took them out of circuit I have been working on restoring a super rare piece of arcade equipment that suffered an electrical fire from a selenium rectifier that went up in smoke (glad I didn't have to experience that smell, it happened to the previous owner) and I am many hours into completely rewiring and overhauling it (the entire wiring loom and transformer were destroyed in the fire)
@DavidLightman
7 ай бұрын
awesome series!, can't wait for the DC bus power up!
@godfreypoon5148
7 ай бұрын
4:39 That's Thallium, not Titanium (?)
@femboichik
7 ай бұрын
Can't wait to see some program running on this beast! That would be so epic!
@paulveitch
7 ай бұрын
The best computing museum in the world is in Bletchley in the UK
@stevew8233
7 ай бұрын
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.
@cokesandwich1668
Ай бұрын
I became nervous when you decided not to replace those electrolytics. They're approaching 70 years old. I'd close my eyes before powering those up.
@DonnyHooterHoot
7 ай бұрын
My dogs tail goes bonkers when he sees the Chewy box. Sorry about the vase. Cool viddy so far!
@frankowalker4662
7 ай бұрын
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.
@andygozzo72
7 ай бұрын
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
@frankowalker4662
7 ай бұрын
@@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
@andygozzo72
7 ай бұрын
@@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?
@frankowalker4662
7 ай бұрын
@@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.
@andygozzo72
7 ай бұрын
@@frankowalker4662 grundigs usually had internal fuses anyway i have a TK20, used to have a couple of others but sold them some years back
@jamessmith4229
7 ай бұрын
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.
@PixelBrushArt
7 ай бұрын
Can't wait for DC!
@telmore6490
7 ай бұрын
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
@nathansealey6270
7 ай бұрын
Totally agree!! Only change a component when it’s failed otherwise your are just creating waste
@michaeldemel4934
7 ай бұрын
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.
@Ghandacity
7 ай бұрын
7:24 - That looked like the magic smoke broke out!
@martinleska4292
7 ай бұрын
Probably not, looks like old rubber grommet for cable protection to another side of metal plate releasing black color
@kerryedavis
7 ай бұрын
The PDP-12 might just be the most beautiful computer ever. Perhaps tied with the PDP-15.
@byterock
7 ай бұрын
Hmm I would put a resistor as well as a diode as in this case it would increase you plate voltage so those 2D21s might not turn off/on as expected. Looking at the Datasheet at 160v plate the operation curves are all quite non-linear all depends on the voltage on the grid (1) if it Negative then you have good linear curve a positive value get you into funky town. The old guys at the radio club swear that the high voltage heavily stressed seleniums rarely blow it is the lower voltage (30) are the ones that go. I would check the voltages first but you are most likely right there is no need for a resistor.
@KAPTKipper
7 ай бұрын
@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."
@splitprissm9339
7 ай бұрын
Found very similar looking actual capacitors in an (ultimately deemed beyond economical repair for different reasons) 1960s lab power supply - *they weren't leaking and measured fine* (capacitance, ESR, leakage current at nominal voltage), it was just the insulating plastic that had degraded in an incredibly icky way. Can be slit with a utility razor and removed - though the glue residue on the capacitor body is hard to get off, stoddard solvent and paper towels will get most of it off (likely including the printing :( ) but not quickly, then the parts can get a new heatshrink...
@NathanielStauber
7 ай бұрын
At 4:40 when talking about the titanium drum, the table is showing the price of thallium. While i had the video paused, I noticed some of the massive price increases! It makes me wonder what happened to the thallium market in 1981, 1989, and 2006.
@NathanielStauber
7 ай бұрын
I see you've responded to someone else pointing this out, seems like an easy mistake to make in what I presume was a large document.
@raelik777
7 ай бұрын
Just FYI... that dollars per pound list you put in the video @4:40 was for thallium, not titanium.
@UsagiElectric
7 ай бұрын
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!
@raelik777
7 ай бұрын
@@UsagiElectricHEH no prob, just figured you'd wanna know!
@user-nd8zh3ir7v
7 ай бұрын
its very cool just to see this stuff, and how it was constructed!
@jobalisk6649
7 ай бұрын
Aside from the collosus the only other thing I can think of that was using photodiodes at this time frame was the Soviet Luna 3 which used photodiodes to scan the photos it took of the far side of the moon and send them back to earth via radio. That was 1959
@Rorschach1024
7 ай бұрын
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.
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