Alignment...

As I mentioned in my last post, my FRG is in need of alignment - tuning at the bottom of each band is cramped and non-linear, it falls about 50kHz short at the top end of each band (when it should go about 50kHz past the end), and the whole thing feels a bit insensitive (which may just be psychological on my part).

That's not unusual; as far as I know, the set has never been aligned since it left the factory 30-odd years ago, and being kept for a few years in a hot shed won't have done it any favours.  At least it hasn't been "adjusted" by someone who's skills would be more in demand in the meat production industry than in an electronics workshop. Alignment isn't hard, and is quite well documented in both the instruction and service manuals, but it does require a few tools and a certain touch…

The (slightly grainy) taste of success

(As I mentioned earlier, this and previous posts are re-worked versions of posts originally made late last year.)

Straight after I finished building, testing, & installing the new PSU, I hooked the laptop up to the FRG-7700 and decoded the following images:

Curing the power supply blues…

Original FRG-7700 power supply board.

Like most (but not all!) things, there's a lot of info about Yaesu SWL/ham gear on the internet. For starters, there's the Fox Tango International Yaesu Users Group (ye olde 80's style design!) including Wim Penders' Yaesu FRG-7700 Survival Guide, and the FRG-7700 specific Yahoo FRG-7700 users group. I'm sure you can find more…

I fully expected to find an improved power supply design somewhere, and was little surprised when I didn't. Not that it's an especially difficult thing to design, but simply because these sets are still quite popular (check out the ridiculous prices on eBay!), are now getting on into respectable middle-age, and many would be owned by people unfamiliar with electronics. The only example I could find is Wim's design in his Survival Guide - and it's deliberately more of an update/copy of the original design, with the 13.5V rail still unregulated but a LM317 regulator IC replacing the zener/Q02/Q03 discrete regulator of the original. I'm not sure why there's no other designs for improved supplies - maybe it's as simple as most sets are in the USA with 110/120VAC mains or, like Wim, are in Europe with 220V mains? Perhaps the transformer's primary voltage select taps are better suited to those voltages rather than Australia's 240VAC, resulting in the 13.5V rail being somewhere near what it should be?

Awakening the sleeping monster

Top view, showing the main board.

Here's the thing with old electronics: don't just turn it on and see if it works! Components degrade due to heat &/or moisture, vermin get in and eat important bits, corrosion destroys wiring & pc board tracks, etc.

And that goes double if it's been sitting in a hot shed with 40+°C temperatures in subtropical Queensland.

So the first thing to do was take the lid off my receiver and have a look…

Something old is (re)new(ed) again

So... I decided to go searching in the shed and dig out my old shortwave receiver.

Up, running, & tuned into a local MW NDB

I bought my Yaesu FRG-7700 second hand back in ... what was it, 1996? ... when I was still an electronics technician. At that stage I'd been a hobbyist for many years, with a passing interest in shortwave listening for all that time. When I was a kid I had a Tandy (aka Radio Shack) Science Fair "Three Transistor Short Wave Radio" kit^* which, despite being a finicky regen design with no proper tuning scale (and so to my young mind not a real radio) had fascinated me with its strange languages and odd non-voice signals. Later, as a teenager, I owned an old ex-Army "Reception Set R210" - which, with its calibrated(-ish) dial and SSB reception, was finally a proper radio^**. That set, coupled with a simple FSK decoder kit^†, introduced me to the world of RTTY and WeFax.