The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Thanks for the help! I already figured it out for the Grant and the 139xlr.. I now have 1/2 watt to 8 watt dead key on the Grant with swing up to 25 and 1/2 watt to 7 watt dead key on the 139xlr with swing up to 20 watts!! The way I make the variable super mod with the rat shack TIP120 and a 100uf c...

I owe a big thanks to the man with the plan.... Thanks Rick! I followed your instructions to the T and I have the 'Ole 139XLR recieve up to par! It in combination with the Shooting Star I put up is really something to enjoy! Now if you have an idea on how to install variable power in this radio I wo...

Ok here is a good puzzle for the more experienced Techs..... I have a Firebird F-500. It has 4 tubes (1 driving 3). It has 3 switches and two knobs on the front... the first switch is Standby and Transmit... the second is Power on and off.... the 3rd switch is AM and SSB. The two knobs aren't marked...

RICK IS THE MAN!!!! So many thanks again Rick!! You are truly a good man! I have read through alot of this forum hoping to learn something that might be useful and the one thing I see repetively...... You being a generous person and taking the time out of your day to read and research other peoples...

Yeah I know it's not the best thing to do.... but not having a Tech close by I don't have alot of options.... I tried the preamp on a small linear and it made great improvements over the current RX... I thought if I could install an onboard preamp it would take away the need for running the linear p...

Does anyone have any good ideas for a homeade internal earkit that actually works like it should?

If so could you tell me how to make and install one in a 139XLR?


Thanks in advance!!

I used to make a variable power mod on some of the Cobra and Uniden mobile radios using a transistor (rat shack part #TIP 120), a resistor, the RF gain knob or other comparible pot. Installation was pretty close to the same in them all! I would like to do the same or a similar mod to my 139XLR.... d...

Thanks a bunch Rick! Unfortunately there aren't any good techs in my area! All the good ones within a couple of hours of home have all passed on or retired! I'm putting up a Shooting Star beam tomorrow.... if I don't get the RX gain from it that I'm hoping for then I guess I'll have to run a pre-amp...

ok I looked up TR4 and TR11 and found them to be 2sc945 NPN type transistors.... so I tested them with the diode setting of my DVM and found the following: TR4 shows E-C doesn't register anything with + on E and - on C E-C doesn't register anything with - on E and + on C E-B doesn't register anythin...

Thanks a bunch Rick!!! I've checked RF gain and it is working 100%, checked the adjustments on VR2 and VR3 they are both fine! I checked D1, D13, and D14.... all are good! Please excuse my ignorance here... but how do I test C211, TR11 and TR4? VR5 from what I see on the schematics is the AM RX Gain...

Ok guys and gals... I am a little new to this troubleshooting side of the radio biz!! I have a little basic knowlege of how circuits work and how to peak and tune and all that and I follow directions well!! :wink: So here is what I have that I need help with... Recently purchased a 139XLR... the goo...