Repairing a customers Brymen BM786 multimeter, and investigating the cause of the InEr error message on the input jack alert feature.
Plus a giveaway to a local youngster.

00:00 – A returned BM786 Multimeter with InEr error message
03:23 – Split jacks and input alert circuit
05:19 – In-Circuit probing TIP and Low Ohms mode.
07:19 – A clue?
08:05 – A need a new desoldering gun. Removing the input jacks
10:30 – Bodge testing of the input detection threshold
12:38 – Not one but TWO failed Megger Insulation meters!
13:50 – Megger testing the connectors at 500V
15:19 – Testing a 2nd failed InEr error meter
17:00 – Cleaning the input jacks
19:11 – Heating up the input jacks
20:18 – Getting desperate, removing the input jacks
21:49 – Getting really desparate, removing the input resistors
22:38 – Reassembling the original repaired unit
24:26 – Repaired BM786 GIVEAWAY

Keysight OLED meter repair: https://www.youtube.com/watch?v=CKdeqqo2diI

Forum: https://www.eevblog.com/forum/blog/eevblog-1663-bm786-multimeter-repair-iner-error-investigation/

This was going to be a repair of a vintage Tandy 200 Portable Computer…

Forum: https://www.eevblog.com/forum/blog/eevblog-1662-vintage-tandy-200-portable-computer-claytons-repairteardown/

00:00 – I sear this Tandy 200 had a problem…
02:54 – Teardown
03:57 – The new BM2257 Multimeter
05:25 – I think it’s the buzzer
08:06 – Microscope teardown
16:20 – They don’t make service manuals like they used to
25:57 – Try to reproduce the fault

The difference between Time Domain and Frequency Domain in AC circuit analysis.

AC Theory Playlist: https://www.youtube.com/playlist?list=PLvOlSehNtuHvD6M_7WeN071OVsZFE0_q-

Forum: https://www.eevblog.com/forum/blog/eevblog-1661-ac-basics-tutorial-part-5-time-domain-vs-frequency-domain/

Part 4 in the AC basics tutorial series. AC applied to resistors, capacitors and inductors, along with Capacitive Reactance and Inductive reactance.

AC Theory Playlist

Review of the new Quick 861 Pro hot air station compared to the original 861DW.

Forum: https://www.eevblog.com/forum/blog/eevblog-1659-quick-861-pro-hot-air-station-review/

It’s important to understand the difference between Mean and Median, not just for engineering, but for everyday life, so you don’t get manipulated by people with bad intentions.

UBS Global Wealth Report:
https://www.ubs.com/content/dam/assets/wm/global/insights/doc/global-wealth-report.pdf

Forum: https://www.eevblog.com/forum/blog/eevblog-1658-tutorial-mean-vs-median/

Almost 30 minutes of tearing down a Samsung 75″ QLED One Connect dumpster TV and trying to power it up to see if it’s busted or not. QA75Q7FNA

00:00 Dumpster Samsung QLED 75″
04:46 – Teardown wasn’t easy as expected…
08:11 – What is this cable retention BS?
11:26 – I’m still at it…
14:22 – Where’s Wally? Follow the voltage.
17:26 – Where do I get 350V DC at a few hundred watts?
21:21 – DIY 350V DC power supply
22:52 – 350V DC right up the clacker
24:19 – I need MORE voltage

Forum: https://www.eevblog.com/forum/blog/eevblog-1657-dumpster-samsung-75-inch-qled-one-connect-tv/

Elecami Wolf videos:
https://www.youtube.com/watch?v=NF-MVDc1K9Y
https://www.youtube.com/watch?v=w_39JC2Dkdc
Trolley Riding videos:
https://www.youtube.com/watch?v=g3A1XNfDxe0
https://www.youtube.com/watch?v=MC_xeEKd5t4
https://www.youtube.com/watch?v=H9erf8rt54s

More Mailbag!

00:00 – DPS Ultrathin DIN 5V PSU’s
https://digitalpowersystems.eu/de/standard-produkte/
01:15 – The Knife
06:16 – USB-C Isolator
https://digitalpowersystems.eu/de/schnelle-und-sichere-usb-zu-uart-kommunikation-dank-digitaler-isolierung-und-esd-schutz-fur-ein-und-ausgange/
07:34 – Zubax FluxGrip FG40 Electropermanent Magnet for Drones
https://zubax.com/products/magnets/fluxgrip/fg40
11:55 – Testing the magnet
14:04 – Drone delivered multimeters?
14:53 – Why did someone send this?
15:46 – Wireless Freakin’ Road Charging
https://www.youtube.com/watch?v=sisD61ohzK0
19:37 – Sponge Bonanza
21:21 – Beelink EQ14 Intel Twin Lake N150 Mini PC

Forum: https://www.eevblog.com/forum/blog/eevblog-1656-mailbag-electropermanent-magnet-din-psus-sponge-beelink-eq14/

You can use almost any decent modern multimeter to safely discharge high voltage capacitor banks WITHOUT a LowZ function.
Forum: https://www.eevblog.com/forum/blog/eevblog-1655-multimeter-tip-discharge-capacitors-using-any-meter/

Transistor Zener Clamp video: https://www.youtube.com/watch?v=BGcKjy_UNQ4

A full 3 hour discussion with the legendary Lee Felsenstein, designer of the Osborne 1, SOL computer, VDM-1, Pennywhistle modem, and the inventor of social media. Covering everything from the Berkeley free speech movement, the counterculture movement, his career, through to Obsorne and how he invented social media with Community Memory.
His book: https://www.amazon.com/Me-My-Big-Ideas-Counterculture/dp/B0DJ8T45F1/
https://felsensigns.com/

Forum: https://www.eevblog.com/forum/blog/eevblog-1654-lee-felsenstein-counterculture-the-computer-revolution/

00:00 – Full 3 hour talk with Lee Felsenstein
08:24 – University of California at Berkeley, and the Free Speech Movement.
29:04 – First Junior Engineer job at Ampex
36:20 – The first hackathons with Richard Greenblatt
37:33 – Hackers, Heros of the computer revolution
1:03:36 – Techical career at Ampex
1:12:52 – Atari Computers and Steve Jobs, Nolan Bushnall, and Allan Alcorn
1:15:00 – He tried to pitch social media to Steve Jobs
1:22:15 – Designing the Pennywhistle 103 modem +
1:25:36 – Marty Spergel selling kits
1:31:53 – Steve Wozniak and how the Apple 1 is NOT a personal computer
1:43:42 – Osborne Computers
1:53:22 – Osborne 1 physical design
1:57:57 – Osborne 1 development timeline
2:01:19 – The Osborne Effect wasn’t what killed the company

Revisiting the alkaline battery leakage testing with a 555 circuit from a viewer.

Forum: https://www.eevblog.com/forum/blog/eevblog-1653-alkaline-battery-leakage-testing-2-electric-boogaloo/

Final results of the first leakage testing: https://www.youtube.com/watch?v=BScnU4BT4xk