The Scourge Of Fake Retro Unijunction Transistors

August 4, 2025 by Maya Posch 15 Comments

We all know that it’s easy to get caught out by fake electronic components these days, with everything from microcontrollers to specialized ASICs being fair game. More recently, retro components that were considered obsolete decades ago are now becoming increasingly popular, with the unijunction transistor (UJT) a surprising example of this. The [En Clave de Retro] YouTube channel released a video (Spanish, with English dub) documenting fake UJTs bought off AliExpress.

These AliExpress UJTs were discovered after comments to an earlier video on real UJTs said that these obsolete transistors are still being manufactured and can be bought everywhere, meaning mostly on AliExpress and Amazon. Of course, this had to be investigated, as why would anyone still manufacture UJTs today, and did some Chinese semiconductor factory really spin up a new production line for them?

Perhaps unsurprisingly, some tests later and after a quick decapping of the metal can, the inside revealed a bipolar transistor (BJT) die (see top image on the left). Specifically, a PNP BJT transistor die, packaged up inside a vintage-style metal can with fake markings claiming it is a 2N2646 UJT.

The video suggests that scams like these might be because people want to get vintage parts for cheap, and that’s created a new market for people who would rather get scammed than deal with the sticker shock of paying for genuine new-old-stock or salvaged components. For example, while programmable unijunction transistors (PUTs) like the 2N6028 are still being manufactured, they cost a few dollars a pop in low quantities. UJTs used to be common in timer circuits, but now we have the 555.

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TDA7000 die shot, with labels. Credit: Ken Shirriff

Reverse-Engineering The TDA7000 FM Radio Receiver IC

August 3, 2025 by Maya Posch 5 Comments

A wristwatch featuring the TDA7000 FM radio receiver IC. (Credit: Philips Technical Review)

During the 1980s a lot of consumer devices suddenly got a lot smaller as large-scale integration using semiconductor technology took off. This included radios, with Philips’ TDA7000 FM radio receiver IC being the first to cram most of what you’d need for an FM radio receiver into a single chip. Recently, [Ken Shirriff] had a poke at analyzing a die shot of the TDA7000, reverse-engineering its functional blocks. How did the Philips engineers manage to miniaturize an FM radio? [Ken] will show you.

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Exploring VersaLOGIC Pre-LSI Logic Cards With The Data/620

August 2, 2025 by Maya Posch 3 Comments

Before the era of large-scale integration (LSI) semiconductor circuits, discrete logic circuits using the common diode-transistor logic (DTL) were still necessary and available in a format that was modular and reusable. [David Lovett] over at the Usagi Electric farm has two great examples that date back to the 1950s and 1960s, showing the jump in technology over the course of a mere decade.

The newer Varian Data Machines 620 from 1966 uses germanium diodes and transistors, while the 1956 Bendix G-15 uses germanium diodes with vacuum tubes, the latter effectively fulfilling the same purpose as the transistors. The main difference between the modules is the density, with a decade of technological improvements allowing for more than double the logic on similarly sized cards and a similarly impressive reduction in power usage.

Currently, [David] is working on reverse-engineering these so-called VersaLogic modules to be able to troubleshoot the Data/620 machine in his possession. The results of these efforts are being published on GitHub. Although you can think of these modules as more or less big versions of the 7400-logic ICs — which began to replace them in the Data/620I from 1967 — some of the circuits on the cards get pretty complex.

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Fusing Cheap EBay Find Into A Digital Rangefinder

July 23, 2025 by Adam Zeloof 1 Comment

One of the earliest commercially-successful camera technologies was the rangefinder — a rather mechanically-complex system that allows a photographer to focus by triangulating a subject, often in a dedicated focusing window, and and frame the shot with another window, all without ever actually looking through the lens. Rangefinder photographers will give you any number of reasons why their camera is just better than the others — it’s faster to use, the focusing is more accurate, the camera is lighter — but in today’s era of lightweight mirrorless digitals, all of these arguments sound like vinyl aficionados saying “The sound is just more round, man. Digital recordings are all square.” (This is being written by somebody who shoots with a rangefinder and listens to vinyl).

While there are loads of analog rangefinders floating around eBay, the trouble nowadays is that digital rangefinders are rare, and all but impossible to find for a reasonable price. Rather than complaining on Reddit after getting fed up with the lack of affordable options, [Mr.50mm] decided to do something about it, and build his own digital rangefinder for less than $250.

Part of the problem is that, aside from a few exceptions, the only digital rangefinders have been manufactured by Leica, a German company often touted as the Holy Grail of photography. Whether you agree with the hype or consider them overrated toys, they’re sure expensive. Even in the used market, you’d be hard-pressed to find an older model for less than $2,000, and the newest models can be upwards of $10,000.

Rather than start from scratch, he fused two low-cost and commonly-available cameras into one with some careful surgery and 3D printing. The digital bits came from a Panasonic GF3, a 12 MP camera that can be had for around $120, and the rangefinder system from an old Soviet camera called the Fed 5, which you can get for less than $50 if you’re lucky. The Fed 5 also conveniently worked with Leica Thread Mount (LTM) lenses, a precursor to the modern bayonet-mount lenses, so [Mr.50mm] lifted the lens mounting hardware from it as well.

Even LTM lenses are relatively cheap, as they’re not compatible with modern Leicas. Anyone who’s dabbled in building or repairing cameras will tell you that there’s loads of precision involved. If the image sensor, or film plane, offset is off by the slightest bit, you’ll never achieve a sharp focus — and that’s just one of many aspects that need to be just right. [Mr.50mm]’s attention to detail really paid off, as the sample images (which you can see in the video below) look fantastic. Continue reading “Fusing Cheap EBay Find Into A Digital Rangefinder” →

Reverse Engineering A ‘Tony’ 6502-based Mini Arcade Machine

July 21, 2025 by Maya Posch 15 Comments

The mainboard of the mini arcade unit with its blob chip and EEPROM. (Credit: Poking Technology, YouTube)

For some reason, people are really into tiny arcade machines that basically require you to ruin your hands and eyes in order to play on them. That said, unlike the fifty gazillion ‘retro consoles’ that you can buy everywhere, the particular mini arcade machine that [David Given] of [Poking Technology] obtained from AliExpress for a teardown and ROM dump seems to have custom games rather than the typical gaggle of NES games and fifty ROM hack variations of each.

After a bit of gameplay to demonstrate the various games on the very tiny machine with tiny controls and a tiny 1.8″, 160×128 ST7735 LC display, the device was disassembled. Inside is a fairly decent speaker, the IO board for the controls, and the mainboard with an epoxy blob-covered chip and the SPI EEPROM containing the software. Dumping this XOR ‘encrypted’ ROM was straightforward, revealing it to be a 4 MB, W23X32-compatible EEPROM.

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A long, rectangular electronic device is shown in front of a book of colour swatches. A small LCD display on the electronic device says “PANTONE 3005 C,” with additional color information given in smaller font below this.

A Spectrophotometer Jailbreak To Resolve Colorful Disputes

July 19, 2025 by Aaron Beckendorf 22 Comments

The human eye’s color perception is notoriously variable (see, for example, the famous dress), which makes it difficult to standardize colours. This is where spectrophotometers come in: they measure colours reliably and repeatably, and can match them against a library of standard colors. Unfortunately, they tend to be expensive, so when Hackaday’s own [Adam Zeloof] ran across two astonishingly cheap X-Rite/Pantone RM200 spectrophotometers on eBay, he took the chance that they might still be working.

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PIC Burnout: Dumping Protected OTP Memory In Microchip PIC MCUs

July 9, 2025 by Maya Posch 8 Comments

Normally you can’t read out the One Time Programming (OTP) memory in Microchip’s PIC MCUs that have code protection enabled, but an exploit has been found that gets around the copy protection in a range of PIC12, PIC14 and PIC16 MCUs.

This exploit is called PIC Burnout, and was developed by [Prehistoricman], with the cautious note that although this process is non-invasive, it does damage the memory contents. This means that you likely will only get one shot at dumping the OTP data before the memory is ‘burned out’.

The copy protection normally returns scrambled OTP data, with an example of PIC Burnout provided for the PIC16LC63A. After entering programming mode by setting the ICSP CLK pin high, excessively high programming voltage and duration is used repeatedly while checking that an area that normally reads as zero now reads back proper data. After this the OTP should be read out repeatedly to ensure that the scrambling has been circumvented.

The trick appears to be that while there’s over-voltage and similar protections on much of the Flash, this approach can still be used to affect the entire flash bit column. Suffice it to say that this method isn’t very kind to the Flash memory cells and can take hours to get a good dump. Even after this you need to know the exact scrambling method used, which is fortunately often documented by Microchip datasheets.

Thanks to [DjBiohazard] for the tip.