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Interesting, I may have to pick up a book about these and try roll my own. Who knows how long my hack job is going to last.

So I'm finished with this amp... I ended up putting the original transistors back and have about 60 watts out, whatever its enough. I did have one issue I didn't notice until I put the amp on the antenna. My relay was staying latched on after I was done keying. So simple fix was putting a 100k...

I think the kl203 is really an AB amp since it has the push pull topology, right? Just checked dave made amps.... maaaaaybe going to try making my own first

I do have one, and thats what I was testing with.

Yeah I need to get some variable caps, I dont have any. This radio is stock not that it matters. I think I may start looking at other amps / making one. Any favorites that you guys have? I do not want anything crazy 100ish watts is plenty. I'm more concerned with clean and reliable signals...

I think I'm about to give up on this thing. I tried different cap values on C13 & C10... From nothing to 100pF-360pF. No major difference, but slight output power changes. then I went to R2 and put the 10k pot in there set to 10k and holy hell it went up to 70 watts! The thing is when i talk on...

Yeah thanks everyone for the input, I really appreciate it!. So my results are similar to what miketa_us said. Going off my radio SWR meter, the SWR is terrible right now with these fets. I think I may play around with different values of C13 and C10. My reasoning being that the fets threw the...

Its only at 25W on the meter now so thats low. If you mean the bias voltage then I don't know, I'll have to check.

It looks to me that R2=10k and R3=3.3k are a voltage divider for the bias circuit and the output is set to about 1.86 Volts... The threshold voltage for the IRF520N is 2-4 volts. So im thinking that I can put a 10k pot in there and tweak it until I regain the power lost. What do you think?

Heeey I fixed it, and guess what it was. The freaking relay. I bought another one off digikey just in case because I saw another thread with the top blown off the relay. I replaced that first and i got 60 watts out (before was <2 watts). The funny thing is the relay ohmed out fine, the relay...

yup thats it soo this amp has the fancy 88 mosfets in it

which cap are you talking about, C15? if i get it running i would give it a try

I got some IRF-520 sitting in a digikey cart for about $1 a piece so its still worth it for me. Maybe I'll get some extras and try building an amp of my own design. I'm going to pull the fets and test them out of circuit. How do you turn down the 980?

Ha they ground off all markings I checked. Yeah I was just measuring voltage with the scope, 18 volts on AM. Is there an error with the schematic? I tried redownloading it and i opened it fine, if thats what you meant. Yeah I do need to do that... Not sure how to turn down the Uniden 980 tho

I agree with that, that's what I measured as well. I think the damage is done, but yes I'll be putting them back. I just wanted to rule out the clamping circuit

So I forgot to mention that I did that first and it seems to be ok. The relay is firing, and I checked and TR1 is pulling the collector to gnd as it should. and checking DZ2 there is about 7.5 volts dc sitting there when keyed up. I even pulled the relay and checked that and it seems ok. You...

So I am new here, and just started diving into repairing my lk 203 amplifier. The amp is putting out less than 4 watts, actually almost 0 watts. It sorta worked when it was new but not well. I picked up a dummy load and a MFJ-822 wattmeter. I am using a Uniden 980 to drive the amp. My CB is...