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the "Made in China" radio. one of them was given to me. it was messed up with a few modifications. it was drifty in SSB. I rewired it back to stock. Then one day, it would not change channels. I found a PLL problem. and found information in this website to this common problem in that...

hmmmmmm! typical problem. sounds like relay contacts. clean the contacts. at the antenna switching contacts. rubbing alcohol and a piece of paper to wipe the contacts, all wetted in rubbing alcohol. when in transmit, all the RF power just arcs through the bad contacts.

Yes, have an 811H I use on the Amateur bands. and I have some amplifiers I am repairing for others. But have built MOSFET class-E H.F. AM transmitters, antennas, transmatches, etc.

back in the late 70's "Solid State Design for the Radio Amateur" was the book for me. It gives examples of designing little RF amplifiers, and shows what you need to know. also some other book, "RF Circuit Design" so Tickfawriver, I am down here near Thibodaux, and also worked in the...

here is a stack of amplifiers I took to "repair" I got two working after figuring out what the last guy did to screwed them up even worse. I don't need this!! Then gave the rest of them back.

yep, somebody screwed it up! Usually on these Texas Star / Palomar amps, I find them not working because it was overdriven. So the T/R relay circuit is burned out, and if the amp has a variable resistor on the RF input, it is burned out also. And then somebody tried to repair the T/R...

I would check out the PLL circuit. check the VCO to be on a certain frequency when radio is set to 28,000 kHz. there is a procedure in CB Tricks.

yes, the FCC is not a law enforcement agency. I had them come to my house with a county sheriff deputy, back in 1993 or so. After I refused the FCC guy with a "little badge" entry into my house, he told the sheriff there is nothing they could do, and they took off. Then I got letters in the...

I was all over inside one of these radios last year. it was worked on by a few. it had over 10 amps current when keyed up in SSB, no audio in, so no RF out, and got hot. the bias adjustments all messed up, on the main board, and the external amplifier. IRF520s were changed, and I believe...

and yes, the 2 watt resistor needed at the input circuit if a few watts of input power, if it is a RF power amp. that was a big hint.

OK, thanks, AudioShock. I got the first unit, got the diagram on CB Tricks. I told the guy that gave it to me that it says it is a "Receive Boost Amplifier" and he said no, that they are a TX AMP. a "little modulator" so I took another look at the diagram, and figured it out quicky...

there is a 75 ohm 2 watt resistor on the input coil circuit. would not need a 2 watt there

but NomadRadio, when these first came out, were they used as a receive pre-amp? ? and people saw that with a few changes it can be made into a transmit linear. but not much power from a 6BQ5. there are two of these in my area and the guys refer to them as "little modulators"

yes, the guy down the road brought me a JB-12 "Receive Boost Amplifier" (cute, ha ha) to repair a few months ago. as Nomad said, the negative bias. pull that 6BQ5 out, don't let it get red. no need for it to be in the circuit at this point. power up and measure around negative 45 volts...

on your VR14. maybe you can get some rubbing alcohol inside the part... turn it back and forth to clean. maybe remove it from the board. a few days ago, I had a Marshall transistor guitar amp. no audio output, due to both the volume and gain pots being dirty. I removed them off the...

yes, I was just looking at replys here.. cool, you found it... stuff did not make sense. now it does. R14 adjusts the carrier level for AM/FM.

let's start from scratch. put the radio in LSB, mic gain all the way down (off, no RF to IRF520s) key up (TX). measure the voltage at all the IRF520 gates. let us know. should be around 3.7 V. but anyways, do this..... Do the bias adjust thing. just to make sure. remove the...

here we go! correct diagram, and pix. Too hot outside here in southern Louisiana for me to go outside. I got nothing better to do! but drink ice tea, cold beer, and work on guitar amplifiers and radios.

the zener diodes D112/D88/89 will keep the bias voltage from going over 5.6 V. And that would be way to high anyways. Usually it is around 3.7 V, but this must be adjusted for current through each IRF520. hopefully you are measuring in the correct spot. the gate lead spot is to the far left...

but maybe not if VR17 is controlling things OK in SSB.