Magnum Delta Force USB Issue

[Ghibli69]

The radio mounts 3 mosfet erf2030, could it be that when the radio starts to heat up one of them, go in auto oscilation ?


from schema I see that they are two mosfet and the driver is a 2SC2166, there is a version like mine with 3 mosfet ?

 

[Ghibli69]

Someone can tell me if this radio comes out of the factory with 3 Mosfet ?
Thanks

 

[Handy Andy]

Hmm...then there is a leaky cap - possibly a leaky disc cap in the audio line that is letting bias from a preceeding stage leak into the next one...on the Delta Force, there are several "blocking" caps and all are disc...

Working from the rear by AM regulator C397 is a Disc 0.047M uF or 473M Disc then the one that takes in the output of the 4558 chip that goes to the AM regulator is C263 (?) also a 473M Disc.

The age of the radio makes these audio components suspect

Then too, is Q182 a AM/FM SSB switch - when you toggle modes this is supposed to kill audio and removes it from the AM regulators Audio line.

Then there are several Electrolytic caps in the RF section TX side at the rear panel that can also cause this oscillation effect.- C262 2.2uF as well as their DISC caps...

 

[Handy Andy]

The MOSFET for 2166 - since 2166's are not available easily and cheap anymore - yes it's possible...


Check it's bias - no more than 3.2V to start - in any mode SSB works best for this...measure right at the gate use a dummy load and keep keyups short until you have the thing under control.

 

[9C1Driver]

Someone can tell me if this radio comes out of the factory with 3 Mosfet ?
Thanks

There were no Delta Force radio's made with mosfet finals. The last Delta Force was built in 2002. Now the replacement to the Delta, the Omega Force S45, late in it's run did have mosfets from the factory. So someone has done a mosfet mod/conversion on that radio.

 

[Ghibli69]

To be clearer, the radio is called Delta Force Dragon but is very similar to the Magnum Delta Force. Looking the soldering point are homogeneous I do not think the mosfet has been change.

 

[9C1Driver]

Ok never heard of this Dragon version, must be a knock off or something sold in a different country. If it was built around the same years as the Magnum Delta Force then I would still say no mosfet finals when new.