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The Hewlett‑Packard Z3815A is a GPS‑disciplined frequency reference originally designed for telecom‑grade timing applications, but today it has become a prized instrument among precision‑timing hobbyists, metrology labs, and the broader time‑nuts community. At its core, the Z3815A combines a high‑stability E1938A “hockey‑puck” oven‑controlled crystal oscillator (OCXO) with a robust GPS receiver subsystem, allowing it to…
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In a recent post, I documented the replacement of a difficult to read VFD display with a modern TFT display in my Advantest R6581T. It was unequivocally worthwhile and has been working extremely well. Nowl, I am at it again, but his time the subjects are the HP 3478A 51/2 digits DMM and the HP…
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The Advantest R6581T is an 8.5‑digit, rack‑mount digital voltmeter (DVM) built for high‑precision DC measurements; the T variant is a DC‑only field/rack model (no AC TrueRMS option) and is prized on the used market for lab and calibration work—buyers should expect to source units secondhand and verify display/health before purchase. Overview Notable Features and Design…
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Retro Chip Tester Professional: A Modern Workbench Essential for Vintage IC Diagnostics The Retro Chip Tester Professional (RCT) is a purpose‑built diagnostic platform designed to evaluate, characterize, and document a wide range of vintage integrated circuits—particularly memory devices from the 1970s and 1980s that modern programmers often fail to recognize. Developed in Germany and offered…
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This is a follow-up to my previous post about repairing a Tektronix CG551AP/CG5001 Calibration Generator. The CG551 had been sitting for many months and I thought it was time to give it a quick check. Shortly after turning on the TM5000 mainframe that I had plugged the CG551 into, I was assaulted by the tell-tale…
Shaun Merrigan
Classic Electronic Restoration, Vacuum Tube Audio, Technical History, Photography