Faded Beauty DMM Gets An OLED Makeover

When a fine piece of lab instrumentation crosses your bench, you’ve got to do your best to put it to work. But even in the highest quality devices no component lasts forever, especially vacuum tubes. For some vintage instruments with vacuum fluorescent displays, that means putting up with less-than-perfect digits in order to get that sweet, sweet precision. Or not – you can always reverse engineer the thing and add a spanking new OLED display.

The Hewlett-Packard 34401A digital multimeter that fell into [qu1ck]’s lap was a beauty, but it had clearly seen better days. The display was full of spuriously illuminated dots and segments, making it hard to use the 6.5 digit DMM. After a futile bit of probing to see if a relatively easy driver fix would help, and with a replacement display being made of solid unobtanium, [qu1ck] settled in for the long process of reverse engineering the front panel protocol. As luck would have it, H-P used the SPI protocol to talk to the display, and it wasn’t long before [qu1ck] had a decent prototype working. The final version is much more polished, with a display sized to fit inside the original space occupied by the VFD. The original digits and annunciator icons are recreated, and he added a USB port and the bargraph display show in the clip below.

We think it looks fabulous, and both the firmware and hardware are on Github if you’d like to rescue a similar meter. You may want to check our guide to buying old test gear first, though, to get the most bang for your buck.

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Old Logic Analyzer becomes New PC Case

There are a lot of cool ways to wrap a case around your custom PC build. But the off-the-shelf stuff doesn’t really set your machine apart from the herd, no matter how many RGB LEDs you put inside. If you really want to stand out, think out of the box, and build your PC into the case of an old logic analyzer.

Looking for a little retro cool factor, [Bob Alexander] turned to the world’s boneyard, eBay, and rounded up a dead H-P 1653 logic analyzer. State of the art in 1989 but not worth repairing by [Bob]’s lights, so he proceeded to remove the original 10″ CRT to make room for an alternate display. After a bit of experimentation, he settled on an LCD panel mounted behind a sheet of acrylic that he thermoformed to the shape of the CRT face. All the original guts were removed to make way for the motherboard and power supply, and a custom PCB to interface the original keypad and rotary encoder into the PC. The old buttons now launch various programs and the encoder acts as the PC volume control. The floppy drive made way for a USB hub, the BNC connectors became power and reset buttons, and a photo taken through the CRT bezel before the electronics were removed provides a window into the soul of the original instrument. It’s a really nice build, and totally unique.

Need some inspiration for your custom case mod? This wall-mounted render farm is pretty snazzy. Or perhaps you’d prefer something more apocalyptic, like this ammo can PC.