Anyone know details of RD100HHF1 MOSFETS?

[357]

I have a pro 3 here I bought as parts repair. I suspect a bad final.
Syptoms are low output, I can get 100w if I crank the audio gain to max but ALC on the meter is minimal. I checked the idle current and its 1000ma on 1 final and nothing on the other. the final with 1000ma shows around 4v and the one with no current shows 1.4v. would a bad final make that gate voltage sag? Could I lift the gate leg and check the pad for gate voltage? would it hurt anything lifting the leg and tx on usb no audio?

The main question though is there a difference in RD100HHF1-101 RD100HHF1-102 RD100HHF1C RD100HHF1C-501
RF parts only has the RD100HHF1C-501
From what I can tell, *501 is ROHS and has a bit shorter lead length.
But of all these, are they all the same mosfet?

thanks

 

[nomadradio]

would a bad final make that gate voltage sag?

Has to be a trimpot somewhere for each pair of transistors. I'd say the gate voltage should be set for about 200 mA idle current, keyed with no drive. The low gate-voltage reading is more likely a trimpot that's broken or set too low.

And if there's only one trimpot, a burned resistor on the pair that reads low, maybe? Don't have that schemo handy right now.

73

 

[357]

I found this.
orange is the RD100HHF1-101 black is RD100HHF1C-501
What am I seeing here?

 

[357]

Has to be a trimpot somewhere for each pair of transistors. I'd say the gate voltage should be set for about 200 mA idle current, keyed with no drive. The low gate-voltage reading is more likely a trimpot that's broken or set too low.

And if there's only one trimpot, a burned resistor on the pair that reads low, maybe? Don't have that schemo handy right now.

73

thanks for the reply. they call for 1000ma for each final. voltage at 1000ma is supposed to be 4v
the pot works, no bad resistors. I can find out right away by lifting that gate leg off the board and measuring the voltage again in TX but I'm worried if that might hurt the other mosfet? I think 1 mosfet is toast

 

[357]

I would guess even at 1.4v the final should still draw current, the datasheet calls for 1.5v to 4.5v max.
nobody is home at that 1 final, zero current on tx

 

[357]

So what I can find is the "C" version "offers slightly improved performance in terms of gain and efficiency over the standard version."
So the older version ended with rd100hhf1-102 and the C version starts at RD100HHF1C, *C-103 *C-501 *C-502

So the graph above shows this "slightly improved performance"

and I found this:

and this:

Also the "C" versions have shorter leads

 

[357]

Cant see anything blasted. I see some gold sputtered on the sides? thats solder or something, looks bad at that light but its shiny