Hi Guys. Just bought a Superstar 3900(Cobra 148 rip off) and noticed they've done away with the old 2sc1969 final and replaced it with 2 x Irf520 outputs. Anyway, to cut a long story short, i keyed on fm/am and my power meter shows 10 watts which is fine, however when i talked into the mic on ssb i was only peaking 2 - 4 watts which wasn't good. The only way i could achieve 20 watts or so was to whistle loudly into the astatic mic(i tried several mics to same effect). Even talking loudly didn't achieve more than 4 watt pep. On this note, i decided to open the radio and alter Vr12(ssb power/alc) so that i could voice peak upto about 12 watts or so. It still peaks 20watt or so on a whistle. Having done this, do i need to alter/tune anything else or will me altering this variable resistor have upset any workings of the radio - ie bias, etc. Your comments are much appreciated. Regards. Damian.
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Superstar 3900 & IRF520 finals question
- Thread starter Damo666
- Start date
i usually set my alc inside at 3/4 of the way up.if people say your warrbling i know
i gotta cut it back.also the modulation vr i set at max inside and adjust it at the
mic gain knob. i WOULD turn your am/fm power down to around 5 watts
i gotta cut it back.also the modulation vr i set at max inside and adjust it at the
mic gain knob. i WOULD turn your am/fm power down to around 5 watts
Never play with the insides of a radio unless you know what you are doing FIRST! That's how you turn a nice radio into a trucker special.
I used 2 different meters, an avair and a mfj, both of which are relatively accurate and gave the same readings. The radio came with the irf520 dual mosfets as standard and was bought new. Apparently the superstar 3900 has done away with the old rugged 2sc1969.
Yes, the old rugged 2sc1969 is no longer being made as well as the 2312. This was several years ago when this happened which is why all new Exports now have mosfets. A pair of 1969's right now would probably run 25+ dollars, two irf520's probably $1.25. Might be time to have it checked by a competant tech. Good luck.