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510 will work, but the 520 is my first choice between the two. Many Ham articles can be found using IRF510's for RF output, with a little adjusting of the circuit values the 520 will work and provide more headroom. (anecdotal so take this with a grain of salt.) OEM FQP13n10 seem to spank the...

I thought that part number was for displays that work in the Cobra 25/ PC-68 style radios. I forget if it is commom cathode or common anode. I've bought a few of the blue workman display LED's for Cobra 25 LTD radios, I think with that same part number, but it's been a while and I forget.. It...

If President asked where the "service shop" is located, then saying "In a camper down by the Rio Grande" may not be what they want to hear. I don't repair radios for money, but I do work on some radios for local friends who talk on our home channel. You see RPC, I may not be a "CB radio tech"...

You seem to know all about the con artists out there, how did you forget that soom fools try to mod SMT radios with through hole parts? Does that black goop ring any bells? You and your buddy are so keen on "exposing" people, but honestly you failed to differentiate yourself from a "drugged up...

I've got to ask, why say anything besides "for servicing the unit" when asked? Or is that all you told them?

The President Bill FCC (AM) and President Bill ASC (AM/FM) are two different models, I don't know how much actually differs between the two, but yeah I figure I'd add this to the thread. As far as I know, the schematic and or factory service manual have not been released. I haven't looked for...

I guess the link to that document wasn't easy enough to find in my original post..

Fair enough, why add more parts than necessary! (y) I've been specifically playing with AM only radios that came with BJT final transistors, and adding the MosFet and bias circuitry, and I agree I see no reason to over complicate things. The adjustability of the regulator is very "smooth" IMHO...

I found this on Google; And apparently the new and old PLL function the same? (early 2000's to 2015?) http://downloads.cobra.com/CB/TSB/TSB10085.pdf I don't know if the datasheets are easily found. Edit: I also found this but I don't know if it is very relevant to what you're doing.. ~All...

Good morning y'all! :coffee: To reiterate, if i use a regulator, I should have a (large value) discharge resistor to ground, like 20K or higher? :oops:

The voltage goes to about 0 during receive at the point where I grab it. 8 Volts during TX, this spot would be a good place to connect hard key circuit relay, and feed a jack on the rear of the radio, for those candle boxes i'm fond of. :) (thanks for the idea Tallman!)

No worries, good luck with it.

Tallman, any concerns with the gate voltage being present all the time? I like to switch the bias voltage on for transmit only.

Have you just got this radio recently? If so, I'd have a look at this area: I had a Grant that had a super diode and choke added, and it was one channel off as you describe, I can't remember if the crystal frequency was changed also.. A "super diode" may appear to be factory, but the one I...

That is a fair question, it doesn't take much current. Of course it will dissipate more heat the higher the input voltage. The reason I can say that it doesn't take much current without giving you an actual measurement, is because I've gone down the lazy path on some of my personal projects...

I sometimes just use a regulated bias supply (w/ a choke) with an adjustable voltage regulator, and circumvent the whole "companion component", the voltage present at the "Gate" pin turns on the device. As Andy pointed out, a variable resistor offers the advantage of adjustability, but you'd...

Yeah, I would if I was trying to make my own EKL EN-369. (y) EDIT: Look for less than 4 volts @ the Gate pin when it is all said and done, closer to 3.7 Volts would be better.

VGs on voltage is listed in the datasheet for the device, usually 3.5-3.7 Volts at the Gate pin is okay for most of the common devices used, IRF520, ERF2030, FQP13N10..

I believe 6.3 V was a common filament voltage, time to hit the parts bin!

(y):ROFLMAO: & three out of five times it was likely an "operator error", not every radio is "fool proofed". Add a "power mic" and enough echo, and you can just about overdrive anything, hell even a "stock radio" can sound bad if the user operates in a reckless way (overdriving the audio input).