Repairing the Marconi 2955A (part 2)

After removing the CRT and associated drive electronics, I am now focusing on recovering the video signal using a modern microcontroller. Therefore I have taken some waveforms captures from the three associated signal lines; field sync, line sync and video.

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Repairing the Marconi 2955A (part 1)

As I mentioned in my previous blog post, I purchased a malfunctioning Marconi Instruments 2955A Radio Communications Test Set in the spring. During the summer I tried to start it, but nothing much happened. Random LEDs flashed, relays clicked and CRT did not come on. After a short while a smell of overheated electronics emanated from inside the unit. As a precaution I replaced all the electrolytics in the power supply board AR1, but it had no effect to speak of.

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NMT-450 project, part 4: new test gear

Another year has passed and not much has happened in the development side of things. I have purchased some test gear though. For very small price (100 euros) I bought a (malfunctioning) Marconi 2955A along with the NMT add-on device. Continue reading

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NMT-450 project, part 3: Some silicon and practically no progress

Nothing much has happened in the past half a year. I am having a hard time finding contiguous stretches of time to devote to this project. I have had some international interest. Mainly from countries where NMT has been relevant. It is very nice to hear that people are reading my blog and awaiting results. Continue reading

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NMT-450 project, part 2: FM and LO design work

I have started the project from the ground-up; learning the basics behind all the key systems. The control signalling is pretty straight-forward. You have commands that are prefixed with sync bytes and suffixed by checksums. Nothing special. Continue reading

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NMT-450 BS/MTX project, part 1

Introduction

A few months ago I developed an interest in radio frequency communications. Before that, it has mostly been a complete mystery to me. I read about the subject and figured out basic concepts such as super heterodyning, frequency modulation and so on. To be frank, I knew about different modulation schemes but the actual radio frequency transmitter and receiver was always a mystery to me. Continue reading

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Samsung CLX-3175 DEVE HOME SENSOR ERROR Fix

If you have this type of Samsung color laser MFD, you might have run into this issue. You try to print or copy a page and after a while, the printing stops and you see “DEVE HOME SENSOR ERROR” on the front fascia LCD. What’s causing this and what to do about it? Continue reading

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I²C troubleshooting

Sometimes you might run into a situation when one or more of your I2C devices don’t work. I deal with barometric pressure sensors in my work and these work on the I2C bus. I’ve been banging my head against the wall many times over simple things and mistakes, and that’s why I decided to share some of that “wisdom”. Continue reading

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What happens when a V-groove hits your copper pour

When you design PCBs for work, cost-effectiveness is a big factor. To help you out in the that department, you usually design your board to be a big panel. This panel is then CNC routed to contain a V-groove. This is as the name implies, a V-shaped groove that runs between the individual boards on your panel. When you have pasted, stuffed and reflowed your boards you simply snap them off. This brings in the cost-effectiveness, to be able to process many tens of boards at once. Continue reading

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I²C Address Probe for PICs (CCS compiler)

As a part of my work, I wrote this simple I2C address probe. It’s for PIC microcontrollers, using CCS compiler. (It’s here mostly as a note for myself, but you might find it useful as well.)

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