EEVblog #680 - Mailbag - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: November 04, 2014, 11:03:03 am
content: Mailbag MondayFlux Capacitor T-Shirts:http://teespring.com/stores/eevblogHow NOT to blow up your oscilloscope (Isolation & Grounding):How a Microwave Magnatron WorksPCB HolderMagazine MemoriesMemory StacksIsolated USB-RS232 InterfaceLGB Model Train Controller & DecoderCaterpillar Dump Truck Controller2114 SRAM Memory:http://www.princeton.edu/~mae412/HANDOUTS/Datasheets/2114.pdf

author: klinkerstein
author_rank: Newbie
timestamp: November 04, 2014, 12:12:48 pm
content: Scan of "Engineer is a loner" and the next chapter please

author: Tandy
author_rank: Frequent Contributor
timestamp: November 04, 2014, 12:18:17 pm
content: Yes RadioShack are on life support.Their share price is now below $1 and they almost went under until one of their share holders Standard General did a deal that managed to get them re-financed. The problem is the deal is short term and if RadioShack does not improve profitability by next year then the loans will be called in.It is highly unlikely that RadioShack will be able to turn it round and most financial experts believe it will be out of business by the summer next year.

author: max666
author_rank: Frequent Contributor
timestamp: November 04, 2014, 12:41:14 pm
content: Careful when disassembling a magnetron, the ceramic insulator stems most likely contain beryllium. So do not cut or grind those pinkish ceramics, because dust of beryllium containing ceramic can be quite toxic.

author: bktemp
author_rank: Super Contributor
timestamp: November 04, 2014, 12:51:59 pm
content: Quote from: max666 on November 04, 2014, 12:41:14 pmThis is beeing discussed frequently in forums. Most discussions end with the fact that beryllium make no sense as an insulator in a magnetron, because beryllium oxide is used whenever a good thermal conductor, but electrical insulator is needed. And this is not necessary in a magnetron, because the resonator cavity made out of copper is directly mounted inside the heatsink without any insulation.

author: Gibol
author_rank: Newbie
timestamp: November 04, 2014, 01:36:56 pm
content: Please scan the magazines in your spare time. I would like to take a better look at that. I've spotted the article about BBC experimenting with digital television... wow - in 1974!

author: Rasz
author_rank: Super Contributor
timestamp: November 04, 2014, 02:00:53 pm
content: magnetron dangerous you say?

author: Hade
author_rank: Contributor
timestamp: November 04, 2014, 02:42:03 pm
content: Had a chuckle about your kid watching train videos all day.My little boy went through that exact same phase.I'm always saying how crazy the viewing figures are on those videos.There's literally videos of a kid playing with a toy train that have 30 million views!My daughter's now doing the same thing watching people unbox small toys. I've commented to my wife how similar they are to your mailbag videos!

author: CJWarlock
author_rank: Contributor
timestamp: November 04, 2014, 04:49:11 pm
content: About the RAM stack. The +60K RAM Expansion developed by Mr. Fiz (of Samar, a demoscene group) for the Commodore C64 computer was designed to be done this way. Two additional memory chips were stacked onto already mounted ones with only CAS pins lifted up and wire-connected to some other logic chips (address decoders and so on) which had only +5V and GND pins soldered onto already existing logical chips (and other pins were lifted up and wire-connected to other chips). Here's the description and scheme:csdb.dk/release/?id=110815?. So, stacking chips was a pretty common and easy solution to modify 8-bit computers.

author: craigh
author_rank: Contributor
timestamp: November 04, 2014, 06:46:36 pm
content: Yup, I remember the Intelec8. Used one to burn (sometimes literally!) EPROMS back in 1979 while I was doing some development with the 'new' 8085 microprocessor. Did the editing and assembly on an HP21-something mini-computer which spit out the HEX file onto a paper tape. Took the tape to a Teletype machine hooked up to the Intelec to read in the code and burn the EPROM (256 byte if I remember correctly, or did we have the new 1k byte versions?). Wow, have we come a long way since then.

author: gemby
author_rank: Contributor
timestamp: November 04, 2014, 07:29:37 pm
content: And yes, big thumbs up for Way back Wednesday idea

author: Fungus
author_rank: Super Contributor
timestamp: November 04, 2014, 07:49:59 pm
content: You gotta scan that magazine, whatever it takes.You don't need a flatbed scanner these days, just set up a decent camera and photograph each page as you turn them.Do left side, move magazine across table, do right side, turn page. Use a foot pedal to take the pic.Pay a passing student $5 to do it, whatever it takes...

author: elgonzo
author_rank: Unknown
timestamp: November 04, 2014, 08:16:05 pm
content: Dave, did my old eyes just see an 8-inch floppy disk on your shelf there?Also, i spotted a few males. I think they're winners...or not...

author: jancumps
author_rank: Unknown
timestamp: November 04, 2014, 08:33:44 pm
content: I thought it was New Order's Blue Monday maxi...

author: Yago
author_rank: Frequent Contributor
timestamp: November 04, 2014, 09:24:28 pm
content: Quote from: klinkerstein on November 04, 2014, 12:12:48 pmOhhh yessss!!!!

author: Fungus
author_rank: Super Contributor
timestamp: November 04, 2014, 09:38:19 pm
content: Quote from: Yago on November 04, 2014, 09:24:28 pmHe can't leave us hanging on that one, can he???

author: Yago
author_rank: Frequent Contributor
timestamp: November 04, 2014, 09:46:13 pm
content: Quote from: Fungus on November 04, 2014, 09:38:19 pmThing is, I'm still hoping for some good tips in it !

author: electrocat
author_rank: Newbie
timestamp: November 04, 2014, 10:24:30 pm
content: HiThanks for the PCB holder reviewThere are groves top and bottom to keep the board from droping down.Made some up there for sale onhttps://www.tindie.com/products/Z2instro/pcb-assembly-holder/?pt=directsearchRegardsLeo

author: eV1Te
author_rank: Regular Contributor
timestamp: November 04, 2014, 10:29:39 pm
content: Dave, could you please link to the USB-RS232 converter website? I might want to purchase one for the nice gentleman who sent it in for free, but I can't find it

author: Bored@Work
author_rank: Super Contributor
timestamp: November 04, 2014, 10:41:55 pm
content: Cheap, easy, flexible, universal SMD PCB holder, holds the PCB as flat on the bench as it gets:eBay auction: #400751102673(example only, no need to buy from eBay). Stick the PCB to the bench, solder as you please.

author: elgonzo
author_rank: Unknown
timestamp: November 04, 2014, 11:20:34 pm
content: Quote from: electrocat on November 04, 2014, 10:24:30 pmMuch appreciated that you put your tool up for sale for anyone interested. However, the Tindi price frankly is not very favorable.Flat drill vices with similar 4-inch clamping width can be bought almost anywhere (i guess) for similar or less that price (likethis one with rubberized jaws). Aside from being more robust, the clamping area of those vices is not obstructed by the worm drive. I am not saying that your little tool is not useful. But for the given (Tindi) price i would rather purchase a drill vice, which is equally suited as a (heavy-weight) PCB holder.If you already have a drill vice with flat metal clamps, just get some cheap magnetic rubber or nylon jaws (likethis one) and you got yourself a PCB holder...(Btw, I actually use sometimes a drill vice similar tothis oneas PCB holder. However, this model only has a clamping width of 80 mm / 3 inch.)

author: Macbeth
author_rank: Super Contributor
timestamp: November 04, 2014, 11:34:29 pm
content: Quote from: elgonzo on November 04, 2014, 08:16:05 pmI'm amazed that an early '70s PDP/8 was less than $600. I remember picking one up back in the late '80s donated by an old engineer complete with 640k hard drive and 16k core memory, two mag tape drives, 4 terminals, and a paper tape reader for our school computer lab. The Elfen Safety narks wouldn't allow it to be switched on and so it was sold for the scrap metal and gold pcb value. The wire wrapping those girls did back in the day was utterly amazing. When we did switch it on before HSE jobsworths got involved it had no ROM, so we had to type in a bootloader on the front panel in 12-bit octal, that would fire up the paper tape reader to load in the boot code to fire up the mag tape drives and the HDD that was the size of a washing machine. Eventually the TTY terminals would flicker to life with DEC OS/8. Amazing to see compared to the BBC Micros and ZX Spectrums we had at the time.Now somebody is going to tell me you could buy a house for $600 back then. Fecking inflation!

author: Stephen Durr
author_rank: Contributor
timestamp: November 04, 2014, 11:52:17 pm
content: Thumbs up for the Wayback Wednesday idea. One of my favorite videos was the one where you went through your old magazines. I really like seeing the old articles and advertisements and listening to your commentary on them. Please do more!

author: richfiles
author_rank: Regular Contributor
timestamp: November 05, 2014, 05:03:56 am
content: Gotta love those old mags! I saw things i own in that magazine! I happen to have two Monroe calculators, a 1920 and a 1930, like the one shown in the ad at 42:10 in the video.The 1920 is broken, but my 1930 works flawlessly. Functionality was quite unusual... You selected the function you wanted to use with a switch. There were two banks of functions, so you could have two functions selected at a time, and then you had an action key for each switch to execute the function selected by the switch. This allowed them to have far more functions than actual keys.I personally love the idea of a Wayback Wednesday! I LOVE retro gadgets. I've got calculators front the mid 1960s, and even parts from a thyratron TUBE calculator! Oh yeah, the drive for that 8 inch floppy is sitting next to the SCM Cogito 240SR on my bottom shelf of the second pic!

author: thismuchvolume
author_rank: Newbie
timestamp: November 05, 2014, 05:56:59 am
content: I was pretty excited to see him whip out that box with the Caterpillar power edge logo on it. An EMS display! I work for Caterpillar as an engineer and have been wanting to send something in to the EEVBlog for a long time but I never could decide what.Now, a little info:Those things you were pressing as if they were switches are actually just a partially opaque insert over LEDs. Those are used for indication of things like a charging problem, seat belt not buckled, check engine light, or any other indication we might want to show the operator. These displays are commonly used across all different machines, and the insert is changed depending on what makes sense for any given machine to show. That way they only have to manufacture a single display and use it all over the place. Caterpillar is big on part reuse. This display is intended to be partnered with a few other modular display pieces that show tachometer, ground speed, odometer, and other useful data. They are all in the same form factor and can link up through a communication bus to each other. I've attached a unfortunately small picture of several of the displays working together. You can see near the top right of the picture is the particular display that Dave as given.As for doing a teardown on this thing, I'll ask one of our ECM Hardware guys if there is a trick to getting that screen off. Since our ECMs are really well sealed against environmental ingress, they are also a pain in the butt to open up and work on. Usually the method involves a sharp chisel and a large hammer, then a series of flathead screwdrivers/prybars.If anyone has any questions about it or anything related I'd be happy to try to answer what I can.Also, this finally spurred me to register here rather than just lurk! First post, woo.

author: coppice
author_rank: Super Contributor
timestamp: November 05, 2014, 06:00:13 am
content: Quote from: Macbeth on November 04, 2014, 11:34:29 pm$600 bought you the bare CPU of a very simplified PDP/8. $600 wouldn't buy you a house in those days, but it was quite a lot.It might be more interesting to compare the $572 price tag for the PDP/8 CPU with the $299 price tag of a digital multimeter in the same magazine. The think how expensive a simple multimeter was at that price. In those days a 100MHz scope was about a years salary for a fresh grad.

author: Fungus
author_rank: Super Contributor
timestamp: November 05, 2014, 09:50:04 am
content: Quote from: Macbeth on November 04, 2014, 11:34:29 pmThat would be the bare CPU with nothing more. The price would go way up as soon as you add storage, memory, terminals, etc.

author: mario001
author_rank: Newbie
timestamp: November 05, 2014, 11:47:24 am
content: Hi Dave, hi all,thanks for the review of my isolated USB UART interface!I didn't put it under a specific license, but yes it is open hardware and anyone may use the whole thing or parts of it freely. The documentation and some additional pictures can be found on my homepage,www.mario001.de(german language). I will soon upload the english translation (that was seen in the video), too.@eV1Te: Sorry I do not sell the interface, but I still have some unpopulated PCBs. Just send me a PNRegards, Mario

author: guido
author_rank: Regular Contributor
timestamp: November 05, 2014, 05:50:40 pm
content: Hi Dave,i recognise the meter in the magazine. If you could scan the page, i would be grateful.I have two, 5.5 digit andverynice panaplex displays. Much nicer than the photo. It is quite a novel design for the age. The auto ranging is very slow, it takes nearly a second to change a range.Unfortunately one has a broken panaplex display (+8 section). Got a replacement but that did not last long. I could change it to an LC display (for the moment, sub pcb which can be swapped). There is a whole array of counters daisy chained, so instead a small micro and a hardware counter could count the value for one conversion and display it on an lcd. A small pic would be sufficient. But i don't really need it working...I replaced all caps in both, they were leaking badly. Still need to calibrate them agains the HP in the photo.

author: kc0ngu
author_rank: Contributor
timestamp: November 05, 2014, 06:42:06 pm
content: Quote from: elgonzo on November 04, 2014, 11:20:34 pmNot sure I understand what is unfavorable about $30.Most (all?) Tindie sellers are small vendors, often making the product they sell at home or out of a small business unit, they are not mass manufacturers or able/want to sell via Amazon, competing with Amazon or worse still Harbor Freight (in USA) is pretty tough for the small guys.Go on release the moths splash some cash and help a small guy out

author: m100
author_rank: Regular Contributor
timestamp: November 05, 2014, 08:21:48 pm
content: 40 min 5 secs in, left hand page "BBC experiments with digital tv recording" That is some two decades before Digital Betacam!TDA 2020 mentioned just to the left of that article, that had somereallyfunky leadout and packaging with staggered pins and a copper block to get the heat away from the diehttp://www.donberg.ie/pics/t/tda_2020.jpgLove this look at things decades ago!

author: eV1Te
author_rank: Regular Contributor
timestamp: November 05, 2014, 10:24:58 pm
content: Quote from: mario001 on November 05, 2014, 11:47:24 amToo bad you are not selling them, I liked the functionality.I am not sure if I have the time to find and then purchase all the components required before I can even start soldering it. Do you still have all the components at home (at least the hard to find ones like the FTDI chip, the DC/DC converter and opto-isolator)? Could you could sell it as a kit?

author: cimmo
author_rank: Frequent Contributor
timestamp: November 06, 2014, 02:39:08 pm
content: Yes please for "Wayback Wednesday".

author: Involute
author_rank: Contributor
timestamp: November 06, 2014, 08:53:20 pm
content: Quote from: elgonzo on November 04, 2014, 11:20:34 pmFrankly, I'd prefer Leo's vice as it keeps the board much closer to the bench surface and takes up less space than the drill vice.

author: VK3DRB
author_rank: Super Contributor
timestamp: November 08, 2014, 09:07:15 am
content: You can freeze frame the video in HD and read most of that article on engineers being loners.By the way, it is largely true that engineers are often people with deep social awkwardness. That is one reason why a lot do engineering or computer science because they think they only have to deal with stuff rather than people. A generalisation of course. I was quite unusual in that whilst I was studying electronics engineering at uni, I was into discotheques.