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HP5430A 18GHz微波计数器维修+测试 / Microwave Counter Repair+Testing

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这其实是2019年11月完成的事情，当时拍了一些照片记录，不过因为拍摄环境限制拍得不是很好，就没发出来。最近本科快毕业了，在考虑离开学校的事情，整理了一下自己在学校外租的，专门用来当实验室（事实上更像是仓库）的出租屋。这台仪器作为所有收集到的仪器中个人最喜欢的一台，作为一个纪念，还是发出来了。 HP5430A是HP Journal 1973年第4期的封面产品，这是一款量程覆盖10Hz~18GHz（加选件后可进一步提升至23GHz）的采样式微波计数器。和同期推出的，搭配180系列示波器使用的采样头一样，这台仪器的核心是HP在当时刚开发出来的20GHz采样模块。 实现18GHz的测量并非难事：使用一些微波技巧和当时速度已经足够快的射频二极管，通过混频的方式就可以将高频挪到低频。但是这样做的问题很明显：一个混频器+本振+相关的滤波器只能实现窄带测量，所谓窄带，在当时来说就是300MHz的量级。如果希望测量10Hz~18GHz这样广的频率范围，使用混频方式的成本和制造难度是超高的，只有在频谱仪这类“通用仪器”中才会采用。对于计数器这种需求略有不同的专用产品而言，HP采用了一种基于采样，也就是频域卷积的解决方案，大幅降低了成本。将简单来说：该仪器在工作时，利用采样过程导致的混叠，将微波信号“折叠”到低频，再用普通计数器计数，再去反推原频率。该仪器采用了一个巧妙的方式实现了折叠次数的判断，具体实现方式可以阅读这一期HPJ，Youtube上也有几个视频中有讲解。 作为当时HP微波产品线毋庸置疑的高端产品，这台仪器的售价达到了1973年的$5900，换算到今天就是2019年的$34428.58，约24万RMB。因为当时做高频ESD防护和高频信号限幅很困难，这台仪器的输入保护远远没有现代射频仪器那样完善，真正实现了摸下就死——指现实中的。以至于机器的上面贴了一块金属铭牌，特别强调：“警告：向50Ω输入端输入大于+30dbm（1W，7.07Vrms）的信号将造成严重，且维修费用高昂的损坏”。 温馨提示 因为以上的这些原因，购买前我非常犹豫。这台仪器已知有相当多的故障，前端，也就是价值最高的部分好坏未知。最后还是看在它有辉光管显示屏的份上，付了一大笔运费把它买下了。想着：如果实在没救了，改造成一个超重的辉光钟也不是不行。 首次通电 收到机器，检查变压器设置没问题之后通电测试，状态就和卖家...
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Python Multi-core / GPU Digital Phosphor Rendering of Huge Waveform Data

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Most modern oscilloscopes are marketed as Digital Phosphor Oscilloscope (DPO) because the waveform shown on those scopes looks night-and-day compared to their old counterparts.   DPO vs DSO, from Tektronix TDS784D marketing materials This is because although the traditional DSO can capture data at a blazling fast speed, they lacked the processing bandwidth to show them on the display: It may be able to capture 100 million waveform data for one trigger point and store it in the sample memory, but the monitor only has say 1024 pixels wide. DSO simply throw away most of the points, resulting in an ugly aliased apperarance with 1bit per pixel.   To achieve the nice and smooth look of a DPO, what we want to do is to down sample the 100 million points to 1024 pixels wide with a correct down sampling algorithm.  Recently I've been working with some huge waveform captures with more than 1G points. Plotting such data with the beloved matplotlib will result in an ugl...
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Teardown of an early capacitive tablet: Mitsubishi Grafnet Model 01

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 I recently acquired a very early Mitsubishi drawing tablet. The information I can find online is sparse, so I will tear it down and do some literature searches. Before doing the teardown, I knew nothing about this tablet except that it was made sometime in the 1980s. Cardboard box Accessories My device comes with a pen and a pointing device. At this point, I'm sure it's not based on the inductor resonant technology WACOM is known for: The pen is metallic, with only a very sharp metal tip. The pointing device also has a small ring, the electronic coupling element. This means that the coupling mechanism is not inductive but capacitive. In other words, it's more akin to the Apple Pencil. Later, I found a patent for that pointing device and confirmed it uses a capacitive technology. Also, the pen and the pointing device are tethered, so I'm expected to find a simple signal chain design. US 5,041,820 filed in 1987 by Pentel Co Ltd The tablet itself Taking a peek inside Open...
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Let's Drive LCD - Extras

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Inspired by Wenting, I too have developed an affection for flat-panel displays. However, since the 2010s, the industry has gradually phased out these models, leading to a decline in usage. When I began exploring embedded development in 2012, the most popular display module for beginners was still the Nokia 3310 . Today, however, the kids are working with ST7789V IPS RGB LCDs , boasting a PPI of 260 as their first display. It's incredible how much things have changed! There's a saying: "Things become desirable once they're obsolete." A new generation of tech enthusiasts will come to appreciate the unique aesthetic qualities of these older technologies without having to endure their limitations in daily use. In an era when we all carry ultra-high-performance flat-panel displays in our pockets, these vintage modules certainly have a nostalgic appeal that can be appreciated for their design. This is a post of me driving the mysterious LCD or other flat-panel display m...
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Simulink Tricks

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A Collection of Simulink Designs & Tricks Last Update: Nov 22 2024 #1. Edge-triggered Sine Pulse Generator  This waveform turns out to be tricky to make. I got the solution from here:  https://www.mathworks.com/matlabcentral/answers/891622-how-to-create-pulsed-sine-waves-in-simulink-that-turns-off-at-intervals
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Color Profiles

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I bought a Spyder 5 Elite display calibrator. Then, it's inevitable that I will start benchmarking and calibrating all the devices I own. I think it would be nice to share the generated color profiles so owners of those (poorly factory-calibrated) devices can use them to hopefully get a better color reproduction.  As a rule of thumb, without any calibrator or color palettes on hand, you can compare your device with an Apple device (which usually has a good factory calibration and does not have the "vibrant enhancement" BS) to get a sense of its color accuracy. All calibrations are done with the default settings (50% brightness, Gamma 2.2, 6500K) I do not provide any guarantee on the quality of those profiles. Use it at your own risk. Device Name Serial Numbers Profile Coverage Device Panel sRGB aRGB DCI-P3 Wacom DTH-W1310  6CAH000337-715 EDID   ICC ...
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A Modern Reincarination of Graphire: WACOM Bamboo Series Drawing Tablet Reverse Engineering

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This is going to be a short follow-up of the previous article; please read that one before proceeding:   https://www.lithcore.cn/2024/02/wacom-et-0405-reverse-engineering.html . Same as before, all the high-resolution PCB scans have been uploaded to GDrive:  https://drive.google.com/drive/folders/1vGHHMH9WkavLYoCPT2HWrooUTZOjV1wc I'm personally attached to the Bamboo product line because that is where I got started 10 years ago. The Bamboo product line is initially made of cheap pen-tablet products designed for the entry-level market. WACOM intentionally limited the performance of those products to avoid direct competition with their professional Intuos product line.  Interestingly, by the time I started using their products, WACOM had gradually shifted the focus of this product line to experimental and high-diversity products, including mobile phone styluses, ultrasonic pens (The first Bamboo Inkling product), mobile phone applications, and paper-based products (e.g...
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