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RM Italy KL203 troubleshooting
- Thread starter arinkuddy
- Start date
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At least he is learning about the amp and how and why it does what it does. Like most have said, people throw these away and just buy a new one.
For the time and money invested it's just not worth it for all practicality. But for learning experience, it's a good little amp to mess about with as you won't lose your arse if you smoke it some more!! JMHO about that. Keep at it to the poster. You'll get it! Tallman actually truly knows a lot about those particular amps. He has done a lot of work on many of them lets just say. At any rate, like I said, keep at it if it makes you happy and you are learning something, don't let anyone get you discouraged. Yeah we all know they are cheaply made China amps, throw away specials. But they can also be a simple tool to get some learn on with and not break your bank trying. Not saying I've done this, but all the reading I've done on the damn things it sure feels like I have owned a couple LOL! Be safe to the poster and good morning to all of you fine Gents.
73 and God Bless.
For the time and money invested it's just not worth it for all practicality. But for learning experience, it's a good little amp to mess about with as you won't lose your arse if you smoke it some more!! JMHO about that. Keep at it to the poster. You'll get it! Tallman actually truly knows a lot about those particular amps. He has done a lot of work on many of them lets just say. At any rate, like I said, keep at it if it makes you happy and you are learning something, don't let anyone get you discouraged. Yeah we all know they are cheaply made China amps, throw away specials. But they can also be a simple tool to get some learn on with and not break your bank trying. Not saying I've done this, but all the reading I've done on the damn things it sure feels like I have owned a couple LOL! Be safe to the poster and good morning to all of you fine Gents.
73 and God Bless.
arinkuddy,
Keep plugging away at it. As 222DBFL wisely said it is a good one to start out with and if you kill it let me know and I'll donate a fresh carcass for your learning experience.
The circuits are pretty much the same as far as function goes.
One area will key the amp and supply voltage to the finals and so on.
Keep plugging away at it. As 222DBFL wisely said it is a good one to start out with and if you kill it let me know and I'll donate a fresh carcass for your learning experience.
The circuits are pretty much the same as far as function goes.
One area will key the amp and supply voltage to the finals and so on.
Glad to see you got your amp working.
I just got my KL203 working today and have learned a few things. I removed the STP80NF55-06 fets which were installed as mentioned in an earlier post. These weren't working most likely due to their very high input capacitance, which probably caused an impedance mismatch. A low capacitance is optimal. The only other mosfets I had were IRF510's from an RS store closure sale. Soldered them in & added some fresh silicon heatsink compound.
Bench tested into a 50 ohm dummy load using a stock BC980SSB as an exciter & an Autek Research WM1 meter, measured 18w out with dead key 4w in, swings to 80w peak. Not near the specs of a new KL203, but satisfactory to me. Dead keyed at 4w for 60sec and the heatsink barely got warm. I'm done experimenting with this for now.
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Apparently results vary widely, probably due to the variances between mosfet manufacturers and even among fets of the same type.
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 capacitance out of wack.
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 capacitance out of wack.
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 the mic my swr would go from just above 1 - 3ish. Kinda makes me nervous. I have no idea why that made the difference, because it should have been the same resistance. Also adjusting it was no bueno, it gave no change in power and I eventually blew the on board fuse.
Is it typical to have the radio side swr move that much when talking?
I am going to try one more thing then be done with it.
EDIT: I connected the wiper and one other pin of the pot to where R2 used to be. there was one unused pin. Just saying I used it as a variable resistor.
Is it typical to have the radio side swr move that much when talking?
I am going to try one more thing then be done with it.
EDIT: I connected the wiper and one other pin of the pot to where R2 used to be. there was one unused pin. Just saying I used it as a variable resistor.
I'd have used variable caps. And I suspect you won't see any major changes; but as you approach a closer impedance match, the power output should peak. That is what you can do with variables that a fixed cap may/may not accomplish. impedance match is more important than getting a lot of watts anyway, as you can only get so much out the output devices.
If your SWR is off and you are using a 50 ohm dummy load for testing; then the radio being used may well be throwing off the SWR due to harmonic content. This is the reason that tweaking a radio should be done in a way to be sure this doesn't happen. . .
If your SWR is off and you are using a 50 ohm dummy load for testing; then the radio being used may well be throwing off the SWR due to harmonic content. This is the reason that tweaking a radio should be done in a way to be sure this doesn't happen. . .
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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, which is why I got this guy in the first place.
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, which is why I got this guy in the first place.
If you want clean and reliable your going to want a nice regulated AB amplifier. Any of the RM Italy amplifiers really don't fit that requirement. I have had two KL203's, a KL60, and a KL200p. For the money they are nice cheap light duty low end throw away amplifiers. I think most of them are class C. A nice AB amplifier is tough to find these days. Don't forget, you could have a super clean amplifier but if you over drive it and run a clipped or overmodulated radio it will splatter with some of the best Davemades out there. (LOL)
Do you have/use a 50 ohm dummy load?
Pretty hard to work on equipment w/o one.
Antennas don't present a stable load for testing.
Dummy loads are cheap and even easy to build.
Pretty hard to work on equipment w/o one.
Antennas don't present a stable load for testing.
Dummy loads are cheap and even easy to build.
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
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