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In my testing, they do not need to appear to be burnt..granted, one that did appear to be burnt had an swr of 5..another 2 now, appearing to not burnt, are reading 3 and 4..best of luck with your tests..the chokes are 15 bucks or so for 4 on ebay, it's cheap insurance..

Shadetree, I know this is an old post, but I noticed in my trials that when L1 choke gets abused/worn the swr climbs..in other circumstances possibly years of use and/or abuse could cause it? A trimmer cap may be enabling the root issue?

UPDATE!! c22 was shorted, I had 13.8 on my antenna out line. I replaced c2 and the l1 rf choke, went through series of tests for swr, pass through, the gamut. Hooked it up to my test am radio, powered up, no smoke!! 3 watts in, over 100w out, I noticed at that time dial a watt was not working, I...

Are you suggesting that because I could not get my bias up that the 2879s could be fried? My parts cane in, I just replaced c17 with the schematic cap, I think .1 uf, anyhow my voltage just increased to 6.2!! In some ways that is good news, but even if my bias checks out now can they still be fried?

I hated to "like" your comment..but I must, 2 votes for bad transistor is nothing i can ignore.i will pull the legs next and give them a test...shucks..thank you for your input!

That would be sad...i have not pulled the legs to check them yet. I did a test awhile back to see if they're leaking, they are not, still holding true to 13.8 continued through the entire system..i still have 6 or so components to replace on my list, play with some capacitance values, then I...

Well that puts it on great perspective, thank you! That was a ton of information I needed...i think you just instructed me to take educated guesses to as to the diodes used, play around alittle, to see if it changes my bias voltage. The fact that you say the older amps used less power for the...

Update...i have changed all mica caps, starting with c16, one at a time with a test between each. Still 5.4v...all my other ceramic caps and resistors are still in transit. Further testing reveals that after keeping power on for an hour, and keying for a bit with tests (no rf at input/output) my...

Thank you, I hope that I get it solved, so maybe in the future someone else can benefit from the information, I had searched multiple sites, had gotten as far as I could before asking..ive fixed 3 radios all because of a lot of info, but there is not a lot on amps out there..and yes, im.poor and...

Some of the stuff from China is ok, good to know..i will look into those, maybe order tonight, my voltmeters seem to do everything but check capacitance.

Thank you for all your insight ranch55, I have not checked them, in fact I should learn how to do that! i have them on order, including the micas, which i think 16 is..do you happen to know why c15 and 20 would be changed to a silicone diode? I ordered the caps that should be in their place just...

Yes, I pulled one leg.. Yes, I pulled one leg..collectors of pills are getting their 13.8 as well, as it stands I am problem solving how to raise the bias voltage, I think I will order the ceramic caps for most the board, maybe the diodes, replace from the pills outward. It's cheap insurance..

All of the diodes check out ok with my voltmeter, resistors too..maybe I will look at specs on the diodes and make sure their resistive ohms are to spec. I've only been playing with electronics for 2 months now, so beyond what my diode tester says i do not know..

Thank you, im cross eyed from looking at these for a week now...pondering why someone in the past replaced c20 with a diode somewhere I saw a parts list, but have not found it lately. Thank you for your thought!

Yeah, I have a hard time taking good shots with my phone..doesnt matter anyway..i scraped the sludge of with a pic, it wasn't a blown trace. I pulled the board, thought the old pin left from original choke had a cold solder joint, I replaced the caps in that section, new choke, put it together...

Update, same issue in the truck, I found my ohm meter to be .5 high testing on brand new resistors as I went to replace the resistors "out of spec". Bought a new meter, all is well, I am getting 1.2 ohms now on my bias when I hooked them all back on the board, so that's not the issue...what I...

T Thank you, that is some exacting info! Nowhere could I find the tolerances..unfortunatly I'm probably going to have to order the resistors if i find any out of spec, so this may take awhile, I will pull some legs right now and see what I can find.

Yes, exactly! I have a crap newer cobra 29 i use for the tests not going to hook my old Washington up to it till I have it thru multiple test runs! I totally understand the point of the ease it would take to bridge that 1/8 or less gap from board to chassis..i might try to put in my truck before...

Well all of that is good to know..i don't really want to pull the board and shotgun unless I had to. This is a horrible pic I took last night..after i replaced the choke..after a few "tests" the repkacement is now showing an swr of 3 from radio to amp, so i will take it out and clean it up, then...