Teruhiko Hayashi

Every Fox-Tango Legend so far has kept the hybrid era alive with knowledge — survival guides, restorations, stewardship of the club itself. Teruhiko Hayashi, JA2SVZ, kept it alive with a part. Not a part Yaesu ever made, and not one anyone could buy after the factory moved on, but the one component whose failure was quietly retiring more FT-101Zs, FT-107s, FT-707s, and FT-901/902s than any blown final or dried-out capacitor: the OKI MSM9520RS counter chip. When the last of those custom LSIs failed, Hayashi did what the parts market could not. He rebuilt the chip’s entire behaviour in firmware, and offered it to the world from Japan for the price of a pizza.

Yaesu’s late-hybrid generation wore its modernity on the front panel: a six-digit LED frequency display, driven not by boards full of TTL but by a single custom large-scale integrated circuit commissioned from OKI — the MSM9520RS, a 40-pin DIP sitting on the PB-2086A counter board. It was an elegant piece of 1970s engineering. It counted the VFO, resolved the carrier offsets for each mode automatically, and multiplexed the display without recalibration. And then, in early production lots especially, it died. Not occasionally, and not repairably — the chip simply failed after some years of operation, and because it was a custom Yaesu/OKI part, there was no replacement. No NOS stock, no cross-reference, nothing.

The cruelty of the failure was that it killed nothing else. The receiver still heard, the finals still made power, the famously accurate analog dial still tracked — but the digital display, the very feature that defined these rigs against their predecessors, went dark forever. Owners faced a choice between operating a flagship transceiver by analog dial alone or parting it out. For three decades, a dead MSM9520RS was effectively a death certificate.

Hayashi’s answer was a small module built around a Microchip PIC microcontroller — in its mature version a PIC 16F883 running a 20 MHz clock — programmed to simulate the exact functionality of the MSM9520RS. Every counting mode, every carrier offset, every multiplexing quirk of the original LSI, reproduced in firmware and delivered on a board that dropped into the footprint of the dead chip. The early version was a kit for the confident: unsolder the 40-pin DIP, work between tenth-inch pin spacings, allow a couple of hours at the bench. The later version arrived completed and tested, requiring no modification to the PB-2086A motherboard at all. Fast-responding readout, smooth operation, and a display indistinguishable from the day the rig left Hamamatsu.

The detail that tells you everything about the man is the numeral seven. Seven-segment displays can draw a “7” two ways, with or without the top-left segment lit, and Hayashi noticed that Yaesu’s original used segment “f.” So the module defaults to the factory-authentic character shape — and carries a solder jumper for owners who prefer the other. That is not the decision of someone shipping a product. That is the decision of a restorer who understands that the display is part of the radio’s face.

Hayashi’s work did not sit off to the side of the Fox Tango tradition; it became part of its literature. Wim Penders, PAØPGA — Fox-Tango Legend No. 005 — wrote the JA2SVZ module into his FT-101ZD and FT-901/902 Survival Guides distributed through foxtango.org, describing it as the solution to the counter failure that “seems to happen rather often.” On the club’s own FT-101ZD pages, assembled under Carol Maher’s administration, Hayashi is credited alongside Mario Chomicz, G8ODE, as a contributor. Restoration blogs across three continents tell the same story in the same words: display dead, googled the counter chip, found the Japanese amateur with the fix, radio saved.

It is impossible to count how many hybrids owe their working displays to this one operator, but the applicable list — FT-101Z across all three marks, FT-107, FT-707, FT-901 and FT-902 — spans the entire heart of the Fox Tango catalogue. He is the first Japanese amateur honoured in this series, which is only fitting: the radios themselves came from Japan, and so did their rescue.

The Fox-Tango Legends before this entry preserved the hybrid era’s knowledge; Hayashi preserved its hardware. His module embodies the purest form of the amateur tradition — see a problem killing radios, engineer the fix, share it at cost, support it personally — and it did so across a language, an ocean, and thirty years of parts obsolescence. Somewhere tonight, an FT-902 is showing six amber digits because a ham in Japan decided a custom chip’s death should not be a radio’s. His module page remains online for owners who need it: JA2SVZ MSM9520RS Replacement Module.