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Any advice appreciated guys.

Can a 2SC2290 transistor be replaced with a 2SC2879???

I looked at the data sheets for both & the voltages are all identical between Collector/Emitter/Base.

The only difference I can see is the collector current is higher (5A more) on the 2879 (the 2290 is 20A) & the input power is higher on the 2879 (can take 10w PEP)

Will I need to upgrade the driver & re-align the TX coils???

The radio is the Cobra 200 GTL DX (Rev 3)

Many thanks.

I was looking at the data sheets for the two transistors. The only Difference i see is the collector output capacitance is about 200pf higher wich isnt a big obstacle i would think, however the higher drive that it requires is a different story. You may want to look into upgrading the driver to a mosfet like the irf520. You may be able to get the extra drive you need just from that. I would think it would be possible because the mosfets have a higher gain and you should be able to squeaze 10 watts drive pretty easy out of it. I will look into it myself because that would make a nice upgrade to go from 60 pep to 100pep. The only other problem may be heat.

Mike

MIKE

what final is being used in the driver section at Q74? If it is the rd6hhf1 it is only a 6-10 watt driver you will need more than that do drive the new transistors. I would like to see this work though.

MIKE

It's the RD16HHF1 Mike & whilst the drive is lower than that needed to get full output from the 2879, the IMD figures are lower & I'd guess they'd run cooler not being driven hard - that's the logic of the swap, not the higher output (but if I get more as a by-product then it's a bonus!)

ATB

Steve

They can be swapped but the resistor/capacitor feedback between the collector and emitter usually need to be changed to allow for a somewhat greater feedback, or the 2sc2879 can self oscillate. I dont have the exact values for the resistor and cap handy, but I will see if I can give you a recommendation later.

Try and stay with 2290 as 2879 will be more trouble they it is worth.

Thanks Rick - it was just a thought (the idea was to reduce the heat generated by under-driving the 2879 but getting a similar output to the 2290's)

The 200 doesn't have a fan & relies on the heatsink alone.

ATB

Steve