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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.

So have you got this radio going yet? I would check out transistor Q55 that drives the modulation transistor Q54. it may be a tiny surface mount transistor.

ooooh! just took another look at some pix and the schematic again, on CB Tricks. just noticed there is no "mirror board" "shorting board" on the schematic or the picture. This would make it a little more difficult for some, to set the bias on the IRF520s. somebody messed it up. I bet...

I used NTE235/236 many years ago. they worked. Walked into a Fry's Electronics store in and picked them up. but now these NTE's are hard to find. NTE Parts Direct says they have some. ? ? ? DO NOT BUY OFF eBAY / AMAZON 2SC1969 or MRF's or anything like that. all fake.

if them IRF520s are still out of the radio, then power up, and key up the radio. measure the voltage at the place on the circuit board where the gate is soldered in place. Make a note, write down these voltages. let us know. then also after this, turn each bias adjust pot back and forth...

if a "golden screwdriver" tech got in there and adjusted the RF Amp bias pots incorrectly, it would cause this. VR 10/11/20 seen that before......

a friend sent me a few of those kits since he could not build them. and some other LDMOS VHF amplifier. so convert it to what?

so an old post, to a common problem. the first thing to do to any of these radios, especially if somebody has been playing inside the transmitter circuit, and touched by the "Golden Screwdriver" is to check the bias current on the RF driver and final transistors. if this bias is high, that...

yes, give it up on sweep tubes! they are not made anymore.. and give it up on 811 and 572 junk tubes made in China. China (CCP) with their boy Fauci were only good for making long lasting viruses!!!!!! it is even hard to find real working RF NPN bipolar transistors these days. Do not buy from...

I would disconnect the plate high-voltage at the board, or disconnect meter circuit resistor R12. (this resistor usually blows up during a tube failure on these types of amps) a high-voltage probe would be nice to use here to measure. Then "smoke test" also, carefully, and quickly, at the...

I noticed a similar problem on a 2950/2970 main board a few months ago. In the driver transistor bias circuit. I added a 100k resistor to ground. - - from that post: "So looking at the schematic at Q62 there is no resistor going to ground after bias adj pot VR13 to make a correct adjustable...

..... here is a pix of one of the fake 2SC1969 transistors a friend got off eBay. they even have the Mitsubishi logo on them. I think they are some regular low frequency transistors repainted. They do not work very well at 1.9 MHz and forget it up at 28 MHz. I also have some Motorola...

funny, I was gonna call ICA today. a guy sent me 7 2SC1969's from different eBay sources, and they all are fake. do not work. they barley work way down at 1.8 MHZ. this is for a 1.8 to 30 MHz transceiver. So the HG's from ICA are OK. ?????

all the schematics of that radio I see show just one final RF 2312. where can I see this version with 2 finals? I worked on the mosfet versions, very very similar. when You key down in AM, does the 6 V at the shorting board drop down when the RF output drops.?

" --- Just been trying to put it back to stock." Yes, that is what I like to do, back to stock, and adjust the AMC/ALC to maximum for good 100 percent modulation. And also get the RIT back to normal on all these radios..