Tutorials

Interesting Repair Of the Day – Raymarine E120 classic back light repair.

I’m starting to see quite a few E120 classic MFD’s come my way with dark displays – usually because the back light high voltage power supply circuit crapped out. The back light in this unit consists of a number of high intensity, miniature florescent bulbs – commonly known as CCFL’s – or Cold Cathode Florescent Lamps. They require a pretty high voltage in order to illuminate – something in the neighborhood of 1500 to 3000 volts. On the other hand, the current requirement is quite  minimal, perhaps a few milliamps. To create the required power, Raymarine has employed a classic “switch mode power supply” circuit that uses a pair of FETS to drive battery voltage through a pair of step up transformers. It’s quite effective, but my guess is the circuit is running at the top end of it’s design
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Interesting repair of the day: Furuno MU-120C display

I’m starting to see a lot of the Furuno MU-120C displays  come my way with the back light circuit malfunctioning.  Looks like Furuno is having a hard time sourcing replacement boards in order to service them.  Since the unit is composed almost entirely of surface mount components – component level repair is quite challenging – and beyond the scope of most service organizations. Fortunately, I’ve successfully repaired enough of them that I feel very comfortable with the process. Not long ago I was tasked with replacing the LCD that’s used in these units. It had an annoying red line that went down the right 3rd of the screen. Furuno was unable to provide a replacement LCD, but I eventually found a compatible unit from a vendor in Hong Kong. It required a significant effort to transplant the custom made –
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Tentec RX-320 – Total USB conversion. No more dongles!

The venerable old RS-232 port is becoming harder to come by in a modern computer. Yes, USB to serial port adapters and dongles kinda sorta work – most of the time, but they are often unreliable, and can introduce their own brand of headaches into the process. I’ve recently come across a device that can remove the need for dongles and serial cables, and provides for a USB cable that connects not only to the computer, but directly to the radio. It is a pretty serious modification, and only suitable for the technically advanced who have skills repairing both surface mount and through hole circuits, and have access to a high quality vacuum desoldering gun that is absolutely needed to safely perform the job. Or – you can send it to me and I’ll perform the mod for you! More
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PL-259 ASSEMBLY INSTRUCTIONS

The PL-259 was invented in the 1930s by E. Clark Quackenbush. It is sometimes known as a “UHF” connector. It is probably the most common RF connector used in any radio service, and arguably the easiest to assemble. The basic solder on type connector has 2 components: The locking ring, and the main body. This is all that’s needed for most ½ inch diameter coax cables such as RG-8 and RG-213. Smaller diameter coax cables require an additional part known as a “reducing adapter”. Though at first glance, they all look the same, there are several different models of reducing adapters – the difference being the inner diameter or “hole size” is matched to the diameter of the coax you intend to use. RG-58 cable requires the use of a UG-175 reducing adapter. The slightly larger RG-8X cable requires a
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Introduction to Soldering

Soldering is the process of mechanically and electrically binding together two or more metal components through the introduction of an additional metal alloy, that is applied in a molten state. Plainly stated, it is metallic hot glue! Effective soldering requires good heat transfer from the iron to the components to be soldered. Any kind of contamination, corrosion or oxidization – either on the irons’ tip or on the components to be soldered, introduces “thermal resistance” into the process, making the task more difficult (if not impossible) – and time consuming. Remember – the longer heat is applied, the greater the risk of heat damage to to the wire or component, so it’s important to get the job wrapped up quickly. Copper, steel, silver and gold can be easily soldered. For all practical purposes, aluminum , Iron and stainless steel cannot
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