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RM KL503 & SSB compatibility
- Thread starter Dereka5
- Start date
Look for R18 on your K505 schematic.
It feeds the Regulator that "samples" the input and adjusts the drive bias to keep the "Bipolar" "on" but not overdriven where they'd pop.
IN your case, the SD1446 (SD1407) are using this as a ~0.7V to 1V Heavy Current Bias regulator - so they use the TWO 22 ohms to make 11 ohm "cushion" to allow the sampling - then properly regulate the Bias (a precision event) so it's stays in AB - the 503 doesn't have this precision regulator (similar to the LM723) to bias the Gates in the FET's it uses.
It feeds the Regulator that "samples" the input and adjusts the drive bias to keep the "Bipolar" "on" but not overdriven where they'd pop.
IN your case, the SD1446 (SD1407) are using this as a ~0.7V to 1V Heavy Current Bias regulator - so they use the TWO 22 ohms to make 11 ohm "cushion" to allow the sampling - then properly regulate the Bias (a precision event) so it's stays in AB - the 503 doesn't have this precision regulator (similar to the LM723) to bias the Gates in the FET's it uses.
Superb explanation there, @Handy Andy
Why do you think some KL505 amplifiers use 22R, then mine uses 11R (2 x 22 ohm in parallel)?
Not a lot more to say about this KL505, but it really is pretty decent, and reminds me a lot of a Zetagi B550P that I once had. The output power is pretty much the same as that was, too.
Hopefully, it'll be as reliable, because the B550P really was a workhorse.
Why do you think some KL505 amplifiers use 22R, then mine uses 11R (2 x 22 ohm in parallel)?
Not a lot more to say about this KL505, but it really is pretty decent, and reminds me a lot of a Zetagi B550P that I once had. The output power is pretty much the same as that was, too.
Hopefully, it'll be as reliable, because the B550P really was a workhorse.
You're not running with FET's. They would need a higher voltage "sample" that actually works against the principle of Current driven regulation versus voltage driven regulation.
Go back to the 503, you'll see they use a simple Zener to regulate the power to the Gates.
Since Gates are "high impedance" meaning they don't consume power, just need a field to work from to turn on the part laying underneath it - the voltage draw, or power consumed is pretty marginal (More Static than Moving / flowing) - you really only need to source from one simple "3V~4V DC" regulation source of basically milliwatts of power at a given voltage - dropped by a resistor - filtered by caps into a load it sees as a 1K to 10K ohms of resistance at any given time - a 1W to 2W Zener can handle that all day.
The 11 Ohm comes from a "starvation" principle. Think of it as a restriction - 22 ohms would make the SD1446/1407 work more into Class C and get a little too crunchy on peaks - is the greater restriction on the Regulator causing a higher power (Regulation) drop - so they LOWER the resistor by a factor of 2 to increase current power available to meet the needs of the push-pull design. And to keep the regulator from overheating by the Amp draw the SD1446 could pull - they still use the Dropping Resistor to prevent a type of failure caused by power regulation draw - a type catastrophic failure - where the Regulation system could fail - caused by starvation - and push full battery supply into the Bases - then what? BOOM - so they drop current to limit it into the system so if the Regulator failed, you have some warning by performance and how others hear your station - so you can at least look for another one without self destruct engaging the amp and taking out the amp and possibly the radio with it.
I know this from experiences with Tripp Lite and other types of 10~15 amp power supplies that used the LM723 to drive directly the outputs - which is hard under loads - so they really should have done more effort in Darlington style driver regulation for the power regulation pass transistors.
But most of all - enjoy the system!
Go back to the 503, you'll see they use a simple Zener to regulate the power to the Gates.
Since Gates are "high impedance" meaning they don't consume power, just need a field to work from to turn on the part laying underneath it - the voltage draw, or power consumed is pretty marginal (More Static than Moving / flowing) - you really only need to source from one simple "3V~4V DC" regulation source of basically milliwatts of power at a given voltage - dropped by a resistor - filtered by caps into a load it sees as a 1K to 10K ohms of resistance at any given time - a 1W to 2W Zener can handle that all day.
The 11 Ohm comes from a "starvation" principle. Think of it as a restriction - 22 ohms would make the SD1446/1407 work more into Class C and get a little too crunchy on peaks - is the greater restriction on the Regulator causing a higher power (Regulation) drop - so they LOWER the resistor by a factor of 2 to increase current power available to meet the needs of the push-pull design. And to keep the regulator from overheating by the Amp draw the SD1446 could pull - they still use the Dropping Resistor to prevent a type of failure caused by power regulation draw - a type catastrophic failure - where the Regulation system could fail - caused by starvation - and push full battery supply into the Bases - then what? BOOM - so they drop current to limit it into the system so if the Regulator failed, you have some warning by performance and how others hear your station - so you can at least look for another one without self destruct engaging the amp and taking out the amp and possibly the radio with it.
I know this from experiences with Tripp Lite and other types of 10~15 amp power supplies that used the LM723 to drive directly the outputs - which is hard under loads - so they really should have done more effort in Darlington style driver regulation for the power regulation pass transistors.
But most of all - enjoy the system!
- No one is chatting at the moment.
...runna pile-up on 6m SSB