Recent content by nomadradio

The speaker amp chip has nothing at all to do with AM transmit audio. Another job for a cheap outdated o'scope. Seeing is believing. 73

It was Uniden's captive brand back in the day. 73

What I mean by false peak is the behavior of the tuning slug. It reaches the rim of the opening and appears to exhibit a peak because turning it further reduces inductance as the slug rises above the rim. Max inductance gets you closest to resonance without reaching it. Max inductance is...

Didn't change C9? Its directly between the chip's output on pin 9 and the speaker. A 'scope would reveal at a glance if that were causing trouble, just comparing what goes into it with what comes out of it. 73

I think we have one that got converted to use as a VFO on Browning base-station transmitters. Wasn't a good conversion, but that part of it still worked last time I powered it up. Just doesn't drive the Browning hard enough. Can't sell them on fleabay. Always get a nastygram that it's not...

I'm certainly ready for Alan to make the Browning-only parts available again. Greg Barkett stopped selling the day he got paid to close out that stuff. Alan didn't purchase the e-commerce site nor the database that goes with it. Getting it all listed online will take some effort. Just glad I...

So here's another idea that hasn't quite graduated to half-baked. More like half defrosted. Back in the day, if the hired help had a slow day, he would put together parts kits for rehabbing the tube CB radios. The pieces they would need is predictable up to a point. But there is always a fixed...

The six digits are multiplexed. If you hold a fan between your eyes and the display, you'll see a strobe pulsation as the fan blades spin. Only one digit is powered at a time. The individual segments are all wired in parallel. The "a" segment of all six digits are wired together, and so on for...

To turn a "2" into a "6" the a segment has to be shut off when it should be on and the e segment turned on when it should be off. All the later frequency displays wire the digits in an altogether different format from that one. Just not remotely compatible with the display wiring in a pre-1995...

The side-by-side 3-pin headers have the PTT pins tied from one header to the other. The echo board just passes the PTT line from the mike socket through the echo board to the main pc board. It's not connected inside the echo board. A digital echo, however is different. The PTT line will serve...

Never underestimate the power of resonance. 73

I remember a test setup from decades ago that switched a fixed capacitor in parallel with the IF transformer winding. This tester was an oscillator circuit, and the change in frequency could be used to calculate the value of a transformer's internal capacitor. This is a spec you never see on a...

I sympathize. The alternative is to "audit" the assembly and compare every part to the correct type. Not efficient. But maybe a little less inefficient than finding a 'wrong' part the hard way. 73

If either one fails to go close enough to zero, the next question would be which one? The mode switch interrupts power to internal sections of the radio when it's turned. A circuit that's on the edge of cutting out can 'catch its breath', so to speak if the power is briefly interrupted. 73

Used the bridge-rectifier trick on 23-channel radios decades ago for a local quarry. The drivers figured out a blown radio was an unscheduled break. The owner didn't care that the voltage drop reduced the radio's transmit power. The bridge-rectifier trick works for anyone who doesn't have a...