Recent content by nomadradio

Rock on! Those look excellent! Gotta master the art of the v-cut. Looks easier than my sheet-metal shear. 73

A resistor sub box set to 33k leads me to suspect that it's meant to mislead. Might be legit, but the audio-circuit impedances in that kind of radio are typically lower than that. Never could see the reason to tout this kind of mod without actually revealing what it is. Unless he's soliciting...

The mobile amplifier looks legit. The SD1446 RF transistors it uses require very little drive. A typical CB with a single final transistor is probably a good match for it. A "10-meter" radio with double the wattage might overdo it. Or might not. I have never seen an "Earthquake"-branded...

Is this a solid-state mobile amplifier? Can't remember seeing that one. 73

One of the dual audio-chip versions was EPT3000, maybe? There is more than one of them. The Ranger RG33 schematic is posted here, I think. Can't remember the pc board #, but it has the push-pull audio amp and big modulation transformer. 73

We did this to some Galaxy DX2547 radios with a 0.22uf capacitor. And a switch. Not sure where he connected his resistor to do what you see. He coulda been more forthcoming with the "how". 73

I would just as soon keep it broadbanded. Especially to make it compatible to either the 21 MHz Mark 4A first lo, or the 31 MHz in the Mark 3 and older. Better than having to stock two separate versions. Proof is in the results, once I see them. PCBs are due to show Monday 5/11. Still can't...

I'm accustomed to watching the tuning voltage on a 'scope, to see what the tuning voltage is on channel 1 and 40. For that radio, also seeing the transmit tuning voltage at each end also matters. If it's getting too close to zero, or too close to 5 Volts, tweaking the VCO coil to keep the...

Only way I ever learned to do this is first check for 10.24 MHz at TP1. If it's present see if you have 1.09 (I think) MHz on pin 11 of the uPD858 PLL chip. The symptom suggests that one or the other is missing. 73

Yeah, that;s what it was modded to do. Listed it in the swap shop section: https://www.worldwidedx.com/threads/derelict-superstar-3900-chassis.271178/ Seemed more appropriate than this thread. 73

So, this isn't the DX55 radio Big Mike was looking for. Doesn't have a counter display. It's a Superstar 3900 with 1984 date codes on chips inside it. Parts are missing. It has been converted to serve as a VFO for a Browning Mark 3 Sideband transmitter. Probably doesn't have enough drive level...

Found it. The radio's actually a Superstar 3900 from the 1980s. Basicaly a DX55 with sideband. Final, driver and audio chip are gone. Has a RCA socket on the rear for the slider cable on the Browning transmitter. Got some pics. I'll upload them and check back. 73

That's a cool link. Thanks. It's all about a balanced circuit split either side of ground. The split capacitor tunes each side of the balanced circuit with the center tap grounded. 73

This is where a 'scope pays for itself. Some signal is missing from this picture. Question is which one, and why? 73

More than once I have seen a foil trace along the front edge of the front circuit board burn and cut the power to the power switch. Not a common failure, but put a meter probe on the exposed pins of the power switch. If you can't see any DC voltage there, something has overloaded that foil trace...