LD 1x2 ERF9530 mosfet

[Uncle Ronnie 336]

so i have a few mosfet boxes that I homebuilt. i hooked the single up to the double and ended up getting 300Wpep ssb and 80RMS swingin over 250w on AM using a low drive PC 122 with abt 18w ssb and 3 swingin about 12 AM. theoretically 100W ssb and 60AM from that singlebanger driver is too much for the double which is correct without any kind of cooling, so i was heating the sinks of the double up getting longwinded. SO I decided to build a 1x2 with forced air. problem is the mosfets aren't that great or something's choked up here and im only getting 150w, 50rms with a 30w DK. the DK is fine, but theres really not enough swing in this thing. driver uses LC L match on input and output. I suspect it is being choked between the stages, and maybe the output tuning cap should be tweaked idk. its a head-scratcher. the main difference in terms of the mosfets involved is that the single and double have older stamped erf9530s and the 1x2 has newer ones with no restamp and the original letters just sanded off.

 

[Uncle Ronnie 336]

i tried to recreate the individual single and double circuits I previously built into a single package. getting closer to getting an ok tune on it, input SWR is perfect with the L match (6 turn air coil over a screwdriver and 270pf) so i'm thinkin it has to be the caps and the coil leading to them between the driver and double on the bottom towards the right

 

[jtrouter]

i tried to recreate the individual single and double circuits I previously built into a single package. getting closer to getting an ok tune on it, input SWR is perfect with the L match (6 turn air coil over a screwdriver and 270pf) so i'm thinkin it has to be the caps and the coil leading to them between the driver and double on the bottom towards the right

Hello, By any chance do you have a schematic for building a amp using the ERF9530's? I have been looking all over the web trying to find some. My friend and myself have build a couple of transistor amps and a couple of LDMOS amps but of course we had schematics and full parts list. So if you have any could you please send them to me.
Thank you

 

[Uncle Ronnie 336]

i do not. i built a rocketbox250hd kit and started with that, and then made changes like biasing it a little harder. the single mos stage was a whole lotta trial and error

 

[Uncle Ronnie 336]

soo i found the problem. the relay had too much ohmic resistance in the signal path. swapped it out and im now getting much better numbers.

if you do a 1x2 layout with these fets forced air is an absolute must. they LOVVVEEE current, especially in SSB. theres a reason why you don't see many LD250FET palomar boxes out in the wild. its not because people love em. its because either the driver gets overdriven and pops, or everything goes into thermal runaway due to a lack of fan