I recently got a current mode (outp xfmr center tap not bypassed) Class D amp going on 136khz, basically modeled after the W1VD / G0MRF circuits. FETs are 59N25s, 4820p / 10ohm snubbers, 5t+5t / 21t
Hi Eric, What happens to the supply behaviour if you just switch some Cs parallel to the output, say 4x 4700 uF (low ESR) rated at 63V ? Maybe it solves the problem of the supply going into fault mod
Hi Stefan, Eric, this might solve the PS tripping problem, but on the other hand it might also provide the MOSFET the draincurrent it needs to die ;-) 73, Rik ON7YD - OR7T Hi Eric, What happens to th
...yes, might. But also it might not, especially when the critical event happens only once per minute. 73, Stefan Am 25.02.2019 16:09, schrieb Rik Strobbe: Hi Stefan, Eric, this might solve the PS tr
PS: In a current mode call-D PA i would rather expect an overvoltage issue rather than an overcurrent issue (at the power supply). Maybe the sudden stop of the current consumption (100% to 0%) is to
Hello Rik, I have a series of scope captures from my W1VD amp showing huge voltage spikes on the FET drains at the end of WSPR and especially OPERA TX sequences. I suspected inductance was the cause.
Chris, et.al. N1BUG relayed the same information regarding the U3S and class-D amp behavior, so your observation is not a one off... I have a series of scope captures from my W1VD amp showing huge vo
Chris, LF, Yes, although I run mine differently. I use the full output of the U3S into a doubler. I have run WSPR, JT9, and DFCW from the U3S without having any problems. I have also extensively used
Hello Paul. everyone A series of overlapping scope captures at end of WSPR sequence with expensive high voltage / current Wolfspeed FET's that usually survived, into the antenna and into a 10kW dummy
Thanks Chris. After seeing those I wish I had a storage scope. There is much which could be done to get to the bottom of what is going on with these things. If I had the proper equipment I would do s
Chris Thanks for the waveforms ... very informative. Sure looks like something is triggering the input of the amplifier and thus causing the problem. Since the problem doesn't exist with U3S's (which
Jay, Good idea, but it isn't just the sound card. I can guarantee one or more destroyed FETs after sending two or three characters of CW where computer and sound card are not involved at all. I can a
Paul Was this with a continuous frequency source at the input (HP3325A maybe?) and using a keyer plugged into the amplifier key jack? Jay -- Original Message -- From: N1BUG <[email protected]> Reply-To:
Jay, I was using an HF transceiver in CW mode through a down converter. Other FETs were lost at end of envelope while running JT9 with the transceiver in USB being fed audio from a sound card. The la
Hello N1BUG, Just to add things were MUCH worst using a X2 multiplier circuit (Jay's). I now use an exciter frequency of X2 direct both from the U3S, and as of late X2 from the TS-590 into a simple s
Paul Have you run cw from the U3S? I have never run cw from a transceiver through the amplifier ... instead I always attach a continuous source of RF (GPS referenced HP3325A for example) to the ampli
Chris When running Opera here I used the same setup as on cw. A continuous source of RF attached to the input of the amplifier with the Opera signal keying the amplifier directly. There was never a p
I have investigated waveforms at every stage using all three exciters here: exciter output, doubler output, IR2110 input, FET gates, FET drains. I see no difference at any of these points between exc
Don't have a U3S to test with here, but the normal drive chain is: K3 (10.137 khz out) xvtr (137 khz out) 137 khz LPF Doubler (trifilar xfmr, BAT41 schottky diodes) Tuned filter (parallel coil + cap
