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Search results

  1. nomadradio

    Browning Mark 3 receiver. A tough old bird.

    Takes a knockin' and keeps on rockin'. Was the slogan for a local FM rock radio decades ago. Browning's base radios are tough old birds. A lightning surge up your power cord to a solid-state radio may put it to sleep permanently. Or maybe just set part of it on fire. In all fairness, the...
  2. nomadradio

    Browning Mark 3 receiver drift fix.

    They once were lost but now they're found. Got a question that prompted me to search for these pics, and somehow overlooked them. Figured they were a casualty of the last hard-drive crash ten years ago or so. Naturally I found them looking for something else. Here is a procedure we apply to...
  3. nomadradio

    High Voltage hijinks, National NCL2000 style.

    High-voltage hijinks it says. The pics tell the story. Always, always, always replace the bleeder/equalizer resistors when new filter caps are installed. This amplifier is the National brand, model NCL2000. Made from the mid-1960s to the early 70s, the two 8122 ceramic tubes can be driven to...
  4. nomadradio

    Kris brand 5-band "Amatuer" base linear. Seriously.

    Here's an amplifier I had never seen nor heard of before this one came to visit a while back. It's a brand name I really don't associate with legit ham gear. No idea how many of these they made. Or when it was made. Dates visible on filter caps are 1974. Has two 4CX250B tubes in parallel...
  5. nomadradio

    Cobra 2000GTL 10-Volt blues hit parade.

    Today I stumbled across an abandoned project. A "10-Volt Blues" guide to the electrolytic caps we see cause the most-frequent mischief in the Cobra 2000GTL and similar radios. What prompted it was changing all the electrolytics in a customer's 2000GTL clock/counter module. The displayed...
  6. nomadradio

    No-holes mod to add DX2547 channels.

    The Galaxy DX2547 is pretty easy to expand channel coverage. Cut two wires, insert a SPST switch in each wire. Done and dusted. But some customers are choosy about cosmetics. Now and again the 'cheap' solution that puts two small toggle switches sticking out the rear or one side just does not...
  7. nomadradio

    RCI RT-1 MOSFETs WTF?

    Ah, okay. So what's wrong with this picture? This is the tester we use to match Vth every batch of IRF520 and FQP13N10 parts. Yes, it's a new unused RT1 MOSFET. And yeah, both the testers like this one that we use show the same result. My intuitive guess is that the gate-voltage...
  8. nomadradio

    Browning receiver, signal was a bit too strong.

    As the old guys would say "Measure once, cut twice". Checking to see that you have the right coax on the right radio can prevent faults like this. Yeah, this coil is connected directly to the center pin of the Browning receiver's antenna socket. Not sure how many Watts of RF you need to...
  9. nomadradio

    RCI69FFB4 linear 4x2SC2879 schematic.

    Got this from a customer in Florida. Wouldn't say how he got it. 73
  10. nomadradio

    Carrier control for old '858 Zachary T base.

    So here's the answer I wrote to a PM that asked about the carrier control setup shown for the uPD858-type sideband base radios. He wants to add this feature to a Zachary T, an AM-only model with vastly different requirements for this upgrade. Same PLL chip in both the TRC457 and the original...
  11. nomadradio

    A journey of 41steps begins with six diodes.

    They say a journey of a thousand miles begins with one step. This board gets built in several steps. Parts count is 41 soldered-in components. For those who missed it, we built and sell this circuit board to replace and upgrade the Pride DX300 base amplifier built in 1977 and '78. The FCC...
  12. nomadradio

    My Palomar 300A needs six tubes!

    Well, ya better buy eight! Or maybe nine or ten, like this guy found out. These six "strong" Fleabay tubes included three that tested good enough. One that's probably too weak to use. And two with what we call the "Blown Fuse" failure. Seems that using tubes meant to use in a 23-inch color TV...
  13. nomadradio

    Pride DX300 replacement HV transformer. The molasses creeps ever onwards.

    Fixing a Pride DX300 with a failed power or filament transformer used to be simple. Call RF Parts and order a new one. That was then, this is now. They ran out of originals years ago, and any design records of replacements made by Peter Dahl are lost to the sands of time. Those parts never made...
  14. nomadradio

    Bias zener for eight 3-500Z box

    Apropos of nothing, I stumbled across some pics I had lost. They were copied to the wrong folder, and never tracked down. Just the same, the issue of fixed bias for the 3-500Z tube gets troublesome as you pile more and more of them in parallel. Zener diodes are the routine solution, but zener...
  15. nomadradio

    FrankenMaco, back from the undead.

    Yes, back from the undead. This project got its start around seven years ago. We had found that the only viable way to deal with "competition" amplifiers that burned up 8930 tubes too soon was to convert the amplifier to the GU74b russky military-grade tetrode. Svetlana promoted this same tube...
  16. nomadradio

    Home A Pride DX300 is like a 44 year-old box of chocolates.

    You never know what you're going to get. First boo-boo on this job was mine. We install a circuit breaker on the rear panel to protect the small transformer. The Pride's 10-Amp fuse will keep it from burning down your house. But an overload on the small transformer that powers the grid-bias...
  17. nomadradio

    Re-capping the Browning Mark 3

    I posted a step-by-step procedure with pictures, showing the 'scorched earth' business of recapping the Browning Mark 3 receiver and transmitter about 15 years ago. On the CB Tricks forum. Oops. Can't find the copy I should have kept on the local machine. Might yet turn up, but no joy as of...
  18. nomadradio

    RCI2990 sez "I'm melting, melllltiiiiing!

    The RCI2990 should have a fuse no bigger than 4 or 5 Amps in the AC line fuse, right? So what happens if you use a 20 Amp fuse? To start, insulation will melt from the heat of the transformer's wires. In this case, it seems the two low-voltage secondary wires have melted together and...
  19. nomadradio

    Caps that last 50 years? All you need is a time machine.

    This set of filter caps came out of a Drake L4B power supply. Took them nearly 50 years to go bad. Yes the date code really is from 1973. The upgrade used a modern double-sided printed circuit board with snap-in filter caps and rectifiers. All on one board. The one in the pic is only half the...
  20. nomadradio

    Pride DX300 on the 80-meter ham band? Say it ain't so, Joe.

    So here's a problem we see only on rare occasion. The Pride DX300 was sold as a legitimate 5-band ham linear. The design will in fact tune all five bands and perform as claimed. But most of them ended up on 11 meters. Go figure. Oddly enough, the FCC tightened the restrictions on RF amplifier...