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

I hear ya. These are going straight back to the counterfeiters I bought them from for a refund!

Update: I managed to squeeze about 1 watt deadkey out of one with like 2 watts swing lol. I also tried putting one in a Euro3900 (which has 2sc1969 stock) and it did about the same, maybe a little less. Anybody got a clue?

I bought some of the NSC C1969 (10 in all) because I couldn't find any original Mitsubishi 2SC1969's and believed they would be a suitable replacement. However, when I tried one in a radio that originally had a 2SC1969 factory, it didn't do anything at all.... except get a little warm-- no output at...

I just got a Bishop amplifier, made by Digital Sport Systems, a couple of days ago from a friend. It wasn't working right. After checking the thing out, I ended up changing the preamp transistor (when switched on, seems to actually shift the receive off frequency), fiddling around with the relays be...

Pc not switchin on. when i switch on the main power the cpu & smps fan switch on without on without any beep.? there is no display. the 20 pin connector from smps to motherboard when inserted properly then even the cpu fan don't switch on.when i try putting the cable it sometimes switches on wi...

Radio Make and Model: Uniden PRO 510xl PCB Number: PA-402AA 1/3 (i think) PLL Number: SM5124A Test gear available: VOM Symptoms: audio IC gets hot :shock: The radio works fine. I just bought it on ebay. I noticed that while the unit is powered on, the audio IC begins getting warmer and warmer until ...

Thanks guys for all the help. I think I'll try the 2312's out.

I found this on the net: Workman 1969X CB20W 2SC1969 Replacement..... It says that it is meant to be a drop in replacement for the 1969 and will work fine with a properly adjusted bias voltage. I also found some genuine 2sc2312's for 10 bucks. I'm just wondering if anyone has tried any of these and ...

RedEye wrote:Dodge, That radio dosen't use a "needle" meter. 30 years didn't help this time!!!! Heh Heh.....

lol

well, thing is... the tranny is already toast. I would really like to find a 1969 replacement, but aren't they discontinued? If there are any left out there, does anyone know where I could find a REAL one? Or at least a suitable replacement?

I really don't want to hack up this radio!

if anyone needs the PCB number, I'll crack the case back open and find it. thanks.

my euro3900 had a 2sc1969 final that went poop.... i was wondering if anyone could help with info to convert it to an irf520. it has two trannys mounted to the rear heatsink, one was a 1969 and....well i don't remember what the other was, so i'm not sure if it has dual or single finals. each transis...

Found it! It was just a broken wire to the switch.... how'd I miss that???

Thanks for the help, Rick.

Okay... sorry about that. As I mentioned, it is a Cobra 29/NW/ST. As for the PCB number, the only one I was able to find is KEPC-225D. I'm guessing this is probably it. As for the PLL... I'm new to CB repair and I'm still learning, so I haven't a clue where it is. I'm guessing it is one of the verti...

Its stuck at minimum scale. Thanks.

Tried a 2sc1969 final in a cobra 29/nw/st and when i keyed up, it pegged the s-meter until it got stuck.... even when i adjusted VR5. also it showed very high SWR. So I just said screw it and put an irf520 in and it transmits fine. Now the S-Meter doesn't work at all.... even on receive. What should...

What kind of power output did you have when you first finished the mod? When I first finished, before frying my driver :x , I measured around 2 watts dead key and 18 watts swing, not much at all. But after replacing the driver, fiddling with capacitance, resistances, and retuning her, I am seeing a...

timrim wrote:Yes, it will work fine. That is what some of the older versions used.

Thanks. Mine is one of the older ones that used the 1957, but the 2028 seems to work even better!

Okay, it was the driver. I had a 2sc2028 (I think... some of the print was worn off) laying around, so I put in and it seems to work now. Is this a suitable driver replacement? The original driver was a 2sc1957. Also, anybody who has done this mod, what kind of distance have you gotten? I have a 54&...

I just installed an irf520 in my cobra 29/NW/ST. It worked at first and only had a talk range comparable to my TRC-52. So I opened it back up and started expirimenting with some capacitance values. I was futzing around with capacitor values for C62 [I installed a 470pf cap here when I changed the fi...

Hey speedracer, do you know the exact resistance for setting the FET's bias? I was wondering because I was thinking of using a fixed resistor in place of the pot. seems easier...

Wait... have you built this? The reason I ask is are the 3:1 and 1:4 ratio transformers, could they be any kind?

Looks simple enough . Thanks!

I've looked everywhere on the net for a simple linear amp schematic and no avail. I found some plans "for sale", but since I'm on a budget for now, I'd just like to make this as cost efficient as possible. Luckily, I have a few junk boxes full of parts. I'm not looking for much-- about 50 ...

Thanks for the reply. I'm a genuine novice when it comes to electronics and I've not had a whole lot of experience with MOSFETs. If the resistance is high at 27MHz, would that mean that the FET would become less efficient, producing more heat than RF power?

I was considering an IRF520 in my cobra 29, but what about an IRF840? I know this mosfet is capable of around 125 watts max and I certainly wouldn't expect THAT much, but would the 29 produce sufficient voltage to obtain any noticeable results?

Thanks for the info, I'll look in to it .

How hard would it be to add a RB in a cobra 29/NW/ST?

The way I did this was finding the current limiting resistor for the TX led and solder a wire BEFORE the resistor, then solder the wire to the coil of a small 5-12vdc relay. The other relay coil wire solders to the negative lead of the battery connector. Next, clip your speaker's negative lead about...