EEVblog #1313 - Bad Luck Mailbag

Double 13 is worse than normal 13, obviously. More mailbag.

SPOILERS:
Back in the old lab!
Vintage Soviet Union PC.
00:00 - Mailbag
10:42 - 3G modem with a funky antenna.
13:52 - IOMEGA ZIP drive teardown
21:41 - Smoke alarm sensor teardowns
26:58 - Reverse engineering a Cooler Master PSU
34:45 - $1 ebay power adapter teardown gets Widlarized!

Support the EEVblog through Patreon!

Buy anything through that link and Dave gets a commission at no cost to you.

Donate With Bitcoin & Other Crypto Currencies!

[Seegalgalguntijak]

So Dave, why is it that you're back in the old lab? Did you give up the new one? Or just use the old one as an extension to the new one? Somehow, I've never gotten a reply to that... Come on, Dave, take us on a lab(s) tour and explain what you're doing where and why! Pretty please!

[MrElbK]

Thanks, Dave!
I almost lost my package because it wasn't tracked at all. Happy to see it in Mailbag :)
--
Oleg from Kiev.

[tareqsu]

It is not uncommon to have antennas that "look" shorted.
A very basic example is a loop antenna, which is simply a loop of low resistance wire, basically a short circuit.
In fact, most microstrip antennas (The ones printed on pcbs) have a shorting pin or a shorting wall, by putting thees shorting pins or walls (among other techniques) you will be able to make your antenna smaller for a certain frequency.
Of course in reality it is much more complicated than that, and nobody can look at an antenna and tell you why is it shaped that way, except maybe for the basic shapes.
You usually start with some basic antenna shape, add your space constrains, and the software would iterate and optimize by simualting the antenna performance.

[RobertPl]

Dave. Mera's computer was made at the MERA plant in Zabrze Polska in 80's XX century. Mera 7209 was a computer terminal. Designation CM 7209 is a commercial designation, used on the international market; while the symbol MERA 7953 is a designation used on the domestic (Polish) market. Computers ware exported from Poland to other country soviet block

[TechnikZaba]

8:00 A lot of CEMI, - no longer existing Polish enterprise producing microelectronics. Was closed down in 1994. CEMI located in Warsaw produced: discrete components, bipolar systems

[urugulu]

no dave its not 3.3 volts by the looks of it. i cant see a dot anywhere. looks more like 33v for what ever

[badstate]

ZIP was a horrible design. The edge of the disk was exposed in use. When the head got damaged, it would chip the edge of the disk. If you put the damaged disk unknowingly into another drive, the chip in the spinning disk would catch on the new drive's head, breaking it as well. This cycle would continue for every drive and disk you tried. Went through a whole office of four or five ZIP drives and multiple disks one afternoon before I realized what was happening.

[OfflineSetup]

Where my dad used to work (in the 70s) there was a electronics genius who had been at the company for years. So respected that when he died (he never retired) they "preserved" his desk and no one was allowed to sit there. I can't imagine that attitude would find a space in modern companies.

[apatewnayeah]

Time to hang a big poster outside "dump your 70+ inch TV here"

[nathantron]

There's something terrifying but completely normal about some aussie waving around a giant ass knife without a care in the world.

[JerrySmithKociak]

@8:23 - those CEMI chips were actually made in Poland. Prefix means: U - monolithic bipolar IC, C - digital circuit, Y - for professional use. Numbers are familliar, because those are the actual 74xx series IC's. I've got some of those, some are like 30 years old now, and they are still working fine. Greetings from Poland!

[neidan]

CEMI was Polish manufacturer of 8-bit chips, it closed in 1994 :)

[douro]

ES EVM was a series of plug-compatible mainframes first developed in the late 1960s. Both 360 compatible and 370 compatible versions were developed. IBM actually provided software support for these starting in the early 1970s.

The chips marked "CEMI" were produced in Poland and actually use Western numbering conventions. The chip labeled UB880D is the CPU.

[jolilos]

you should do a video wall made from dumpster finds. I mean a big TV is boooring - have some 19", some vertical 30",

[rasz]

7:00 Mera was a polish computer design and manufacturing unit. They started with paper perforators, then calculators, later licensed terminal designs from Swedish company, then TRS-80 clone. After fall of Iron Curtain they managed to stay afloat by restructuring and switching markets to point of sale systems, Today they are still a local leader in this field.

MERA CM 7209 (MERA 7953) is a terminal dedicated to Russian RIAD systems, direct unlicensed IBM System/360 clones.

8:00 Some polish manufactured semiconductors on the PCB. Unitra CEMI UCY chips 74 series. MCY series are microprocessor clones. Unitra CEMI even cloned Intel 8085 at one point. All behind Comecon (cold war) embargo.

[jimmyramkisoen]

That green PTC 30:04 is used as a Inrush Current Limiting. During power on, a high inrush current can occur because the power supply’s link capacitor functions to dampen ripples in the output current. This capacitor acts like a short, causing an inrush of current. The inrush lasts until the capacitor is charged. Length of the inrush current depends upon the power supply and link capacitor.

[sircompo]

That Zip Drive head looks like the voice coil you find on hard drive heads. Miles ahead of stepper motors and not at all how-ya-doin'.

[lhxperimental]

Australia: Where you can hope to find a 70 Inch TV in a dumpster.

[vaguedirector_]

(29:00) ATX power supplies like that typically have this power path: Input filter -> Rectifier -> Active power factor correction boost converter -> bulk 400V capacitor -> push pull or similar transformer based step-down converter -> 12V DC bulk caps and 12v output -> secondary buck converters for 5V and 3.3V outputs.
And some of the newer super high efficiency ones will have some sort of resonant converter doing the 400v DC -> 12V DC stage, which require some proper wizardry to design.

[RobertBardos]

Dave, long time viewer to say, I think you should abandon the tv screen idea or have it up and off to the side as a additional background but not the main event. Dave your fans come to hear u talk about electronics and I personally like when you get the microscope out on interesting tear downs. Walk away from gimmicky bullshit other channels might be doing. Keep it fresh. You are the product. Not a background or a 70 inch tv or whatever. Keep it old school man.