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This project has been the eternal prototype. Each successive version reveals yet another fatal flaw to fix. It started out as a way to use roger beep boards that lack a relay in radios that require the mike to receive. You need a relay for that, since the mike was keeping the receive speaker...

Just discovered that Jeff, W8CQ has been diagnosed with Parkinsons. Same affliction that forced Peter Dahl to retire, and die way too soon after. https://harbachelectronics.com/ Gonna miss Jeff, and the stuff he sold. Both. 73

So here is a rare treat. A Maco 300 with low miles. Upshot of this is that the owner has six good tubes. It's the 7-tube version, but no problem. I won't send a Maco 300 home with seven tubes in it. The fifth final tube comes out. More on that later. Naturally each of the four final tubes...

There was a time when a customer might ask "Is this radio discontinued"? I would answer with the question "Is it in your hand?". If it is, the time that passed from when it left the assembly line, got packed up, sent to customs, packed into a container, shipped across the pacific at 12 knots...

This radio is as old as the Apple Macintosh. Date codes on the chips that have them are 1984. No, it doesn't say "Galaxy" anywhere on it. But only inside it. Sorta. This circuit board number doesn't start with the letters "EPT", but it's the same format and the lowest "3600" followed by...

Talk about a never-ending story. The eternal search for a transformer to run the Palomar 300A you just bought from the neighbor's grandpa's basement. Of course the folks cleaning out the house looked at the 300A RF deck and said "somebody will pay for that". Then they looked at the heavy black...

Here is an item that nobody has seen fit to scan and post to the web. It is a large-format "tabloid"-size publication that had exactly one issue, far as I can tell. Found a local video studio that has a scanner big enough. FedEx Office would have wanted over 120 bucks to scan this behemoth...

Okay, there's a spot to stash manual files on this forum, drawing a blank about where. Got this one scanned. Got distracted partway through talking to another FedEx customer, so a couple of pages got duped. This model was popular 45 years ago, not so much these days. 73

That's "well done", as in marginally burned. Here's an example of "Hownot2" if you decide to build your own Motor Mouth Mauldulator. He only sells the "brain", the small circuit board where the magic happens. All that boring stuff like an enclosure, power cord, DC supply, controls, knobs...

Gotta learn how to make these. The circuit-board vendor we have used since 1999 doesn't offer some of the features this trick requires. Time to learn EasyCad. 73

Finally! Got me a guinea pig. A Palomar 300A guinea pig. Got a good deal, considering it lacks the power transformer. Not a problem. This amplifier will serve as the guinea pig for two design ideas. An outright replacement for the plug-in relay circuit board used in early production amplifiers...

I don't have the patience to produce a one-size-fits-all procedure for the Maco 750. Kinda like "Ford F100". It evolved numerous design revisions. First thing to fix is the High/Low switch. If your amplifier was built with two "Foster's Lager" can size HV filter caps, this needs to get changed...

Here is probably the second-most popular mod to the Cobra 148GTL after unlocking the clarifier: Making a front-panel knob control the AM carrier level. The SWR Cal control is the obvious candidate. It helps that the control's resistance value is about perfect for this. The pics are from the...

The Cobra 148 has now been built by a dozen vendors, with a variety of different main circuit boards, and different control/front panel switch arrangements. There is no "universal" procedure that's correct across all production changes and vendors. So here is just one of them. This radio is...

Recently overhauled a Browning Mark 4A base station that had a blown power transformer. Some genius had "upgraded" a tripped fuse with one rated at 20 Amps. Needless to say this let out all the magic smoke from the power transformer. Made this an expensive repair, even more so than normal for a...

This guy Hollon sure did crank out some amplifiers. This one is another "nightmare box", but not all nightmare boxes are created equal. I gotta give credit where credit is due. This guy's metal and paint work are first class, or close. It's the electronic side where the user runs into trouble...

Here is a substitute for a part made from unobtanium. The power switch used in the Heathkit SB220 was made by a company called "McGill". Was. Not made any more. A bummer if yours goes bad. For years we would fabricate a metal plate to mount in its place, with a 1/2-in hole to mount a...

I considered a title like "see the sausage being made" for this topic. What it's about is converting a 5-tone roger beep board to a "Bump-Bump". For about 25 years we would convert Taiwan-made "Roger K" beep boards. End result was a beep, pause and a second beep. A variable-pitch control would...

Here's yet another relay substitution. This time it's not so much the relay itself that's the reason, but where it's located. The Texas Star DX1600 has eight 2SC2879 transistors, arranged as four push-pull pairs. Texas Star uses four of the circuit board found in their smaller amplifiers, splits...

So here's a good reason to start your own thread to ask a question. I'll be able to find it using the forum's 'search' feature. Somebody asked about the TRC-446 at the end of another thread. Looked at my shop's archives and found a bench file dated 2003. Just can't find the thread where this...