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No, but their name and logo got pirated onto more than one model linear over the years. Who is Cobra gonna sue for trademark infringement when the product has no name or address anywhere on it? 73

The only way to make the three modes line up in the stock radio is to set the three trimmer coils, one for each mode. The crystal you use for extra channels is now in line with those three trimmer coils. When you change crystals, those three settings are disrupted. They exist to match the...

Yep. There's a mod for that, to lock the transmit and receiver frequencies together. A Pluto will require nearly-constant tweaking during a conversation, but that's a different issue. I'll look up the exact procedure next time I'm at work. 73

Had a very-minor brainstorm. Couldn't figure out a way to make our existing keying circuit work with Heathkit linears. Didn't want to have to put a loud attention-getting sticker on the box that says "DON'T USE ON A HEATHKIT". Should work on Drake, Ameritron, AEA, Dentron, Amp Supply and any...

Only if you're near any of them. The standard IF frequency for a television receiver in the early 1950s was 21 MHz. This caused interference issues with the 15-meter ham band. Just too easy for your signal to leak into a nearby TV. The industry moved this to 41 MHz in the late 50s. Fixed the...

Good chance that this is an old meter with a failed electrolytic capacitor. Seems to me it would also have a calibration trimpot for the MOD scale. The production versions are different from decade to decade. 73

Simplest way to expand parallel bits like the 858 needs is a serial-to-parallel shift register. Serial in, parallel out gets abbreviated to "SIPO" sometimes. We used a 74HC165 to control a MC145106 PLL in a design from the 90s. Only needs two output pins from the controller. One for data, one...

Used to service diathermy machines decades ago. A big Siemens model had casters and used a 300-Watt triode in a power oscillator circuit. Another one made by Mettler used two sweep tubes in a power oscillator circuit. It was a lot more compact with the oscillator and antenna combined in a "hat...

6.3 Volts AC into a half-wave doubler. Can't use a full-wave doubler when one side of the 6.3 Volt secondary is grounded. Does the job. 73

Shameless plug: https://www.ebay.com/itm/116094116631?mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5336136228&customid=&toolid=10001&mkevt=1 73

This is why we won't repair a tube-type keying circuit. Feeding the 6.3-Volt AC heater voltage into two diodes and two filter caps gets you just over 12 Volts DC to power a 12-Volt relay and transistor keying circuit. I can make those sensitive down to a couple of tenths of a Watt without...

Believe what you see. Each production run will use whatever tube the factory could buy cheapest in bulk. The socket reveals which one your amplifier takes. The 8908 has an 'octal' socket with eight fat pins. The 8950 has 12 much-skinnier pins. You'll need whatever tube fits the sockets in your...

Switching to FM with a dummy load, or no antenna attached should produce a near-deafening rushing noise. FM receive depends first on the mode selector to supply power to the FM-only receive detector chip IC2. The tuning adjustment L5 has to be set properly to work. Someone just twisting tuning...

The switch we would use is made by Alps. A single deck has four circuits. The 139XLR schemo shows at least 5 sections in the mode selector. Here's a fleabay link to the 8-pole version Has two decks of four circuits each...

Not easily. The tube sockets will have to be changed more than likely. The 8908 uses an octal socket. Not many other suitable tubes built with that style base. 73

Normally I would agree, but there are two fleabay dealers listing that part. https://www.ebay.com/itm/202729538965?mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5336136228&customid=&toolid=10001&mkevt=1...

The XLR series radios date to 1978. Not so different from needing a part for a 1978 car. The dealer won't be any help. Make sure you replace C179. It shorts and damages the relay. Might also clobber the circuit in the mode switch that feeds the final and driver stages. We found a fleabay...

Mouser, Digi-Key, fleabay. We got away from the "baggie" parts when suppliers selling original-numbered parts appeared in the '80s. Had a local parts dealer who would reverse-cross from a NTE/ECG number to an original OEM "2S" part number. His prices were better. But that outfit dried up and...

Wawasee used two kinds of relay. The older version has a skinny 6AQ5A tube alongside the larger tube. This tube senses the radio's RF and energizes the relay's coil. This version uses a relay with a 10,000 or 9000-ohm coil, meant for 100 or 110 Volts DC. NOT AC! There's a difference in...

It's a pretty generic part. Should not be a problem to substitute. 73