got a little toy today...old cobra 19 Plus. it was my first radio and just got the itch to get one. after receiving it and powering it up i noticed there was NO receive and nothing on the signal (led) meter. when i keyed it up the TX light comes on but nothing on the led meter and nothing on my power meter...so it is not transmitting at all. the mic checks out alright and the PA function works. i only have $8 into it so if i have to junk it i wont cry. but it would serve as a nice project radio to learn a little something. my gut is that it is a PLL problem. solder joints check out ok...reheated them just to check. used external speaker just in case too. when i turn the radio on i hear a staticly pop in the speaker but nothing else. i did notice that on the solder side of the board it is hot right where the driver is. thought this might have something to do with it, but i surmise that wouldnt affect RX. any suggestions would be appreciated. -Ice
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no TX or RX in Cobra 19
- Thread starter iceman78
- Start date
well there is a wya to test these and i dont remember how hopefully someone will chime in here but if you see the part # you can either get 1 on ebay or order 1 from rf parts if they still carry them but they may have a minimum 25$ order not sure.this is a common problem with many of these small set rigs usually people short them out or hook them up backwards that ic if i remember correctly is either a kia7217ap or a ta2222ap audio ic.if it is bad you just unsolder and replace it hope this helps and good luck keep us informed.
Yeah, you could try to shotgun the problem by trying to put in a $8 audio chip in this $9 radio. But, it is a project after all - right?
What kind of antenna is hooked up - and does the TX/RX meter show any movement at all?
What kind of antenna is hooked up - and does the TX/RX meter show any movement at all?
you have been a huge help. thank you. my friend has a junk 19+ for parts so i think i might be able to grab it from him. lastly i found online something they refer to as a supertune for that radio. unfortunately the directions are vague. do you have any insight into that mod?
rf meter shows NO movement at all. not on tx or rx. i also had a good radio nearby and when i keyed the 19 i got nothing on the good radio's receive and vice versa. so the 19 is completely deaf and mute
rf meter shows NO movement at all. not on tx or rx. i also had a good radio nearby and when i keyed the 19 i got nothing on the good radio's receive and vice versa. so the 19 is completely deaf and mute
there are several mods for that radio floating around i have done the transistor swap on some cobra 29s with the 25 volt cap and 100k resistor i am not sure if thats the one your refering to but it did yield a low dead carrier 1-2 watts with forward swing up to 7-8 watts average power with great modulation.make sure you ask your buddy about the junk 19 because it may have been junked for the same reason.
yes the transistor is the 2sc1969 that was what i was talking about look around some more and read other similar mods for that radio you may even find pictures that will clear some things up for you.there may be different variations of the same modification to that radio.look around and let me know if its still unclear.
this is what i found:
Supertune: Replace the final with a 2SC1969 unit. Solder a jumper across the diode going from the Audio Transformer to the Driver and Final (this may cause receive distortion at high volumes, remove jumper if it does). Solder a jumper across the resistor going from the base of the Final to the Driver. If a diode has been cut for modulation, solder it back together, or replace it. Adjust the modulation control POT (VR) for 100% modulation (usually between 1/4 to 3/4 way open). Tune output coils for best swing, using a loud, steady "aaaaah" sound into the mic. Note: These radios are superb for clarity of modulation, even on the stock mic.
all the talk of diode going from transformer...would be clearer if they just said 'solder jumper across D18' thats where i will stumble. a more specific instruction or maybe even some pics would be better. however this is the only variation of the mod i was able to find
Supertune: Replace the final with a 2SC1969 unit. Solder a jumper across the diode going from the Audio Transformer to the Driver and Final (this may cause receive distortion at high volumes, remove jumper if it does). Solder a jumper across the resistor going from the base of the Final to the Driver. If a diode has been cut for modulation, solder it back together, or replace it. Adjust the modulation control POT (VR) for 100% modulation (usually between 1/4 to 3/4 way open). Tune output coils for best swing, using a loud, steady "aaaaah" sound into the mic. Note: These radios are superb for clarity of modulation, even on the stock mic.
all the talk of diode going from transformer...would be clearer if they just said 'solder jumper across D18' thats where i will stumble. a more specific instruction or maybe even some pics would be better. however this is the only variation of the mod i was able to find
solder a jumper(piece of wire from one side of the diode to the other side of diode)this increases the voltage to the collectors of the final transistor and possibly the driver transistor i believe.
hi guys,
i recently picked one of these up at a garage sale for 2 dollars, but i havent even turned it on yet.
the audio chip is the KIA 7217 AP.
as for why your radio doesnt work, i always start out doing a full alignment on a radio. that way, you can see how far you get in the alignment before things start not looking right and you will know which area of the radio to begin looking at.
unsolder the final and driver leads from the board and do the diode test with your voltmeter to determine if they are good or not.
here is a link to the cbtricks site. there you will find the schems that you need.
Cobra 19 Plus
you will also find the factory service manual here. in it you will find all the voltages for the PLL so you can check if its working properly.
read through the whole manual, you will learn alot about this radio.
as for the supertune; dont worry about which diode they are talking about because you dont want to mess with that anyway.
they are referring to the anti-spiking diode whose job is to keep large voltage spikes from damaging the windings of the audio transformer.
even if you did jumper it, you would only gain about 1 watt, if that.
not worth the possible damage to the audio transformer, which will be hard to find a replacement for.
the resistor they are referring to is R311, which is a 3.3K ohm resistor.
jumpering this will increase the deadkey. this may be what you are looking for by replacing the final with the 1969, but if you plan to run an amplifier after the radio, you might not want the higher deadkey.
i would try just replacing the final with the 1969 and then just re-align the transmitter. see what that gets you before you move on to other mods.
if you find that R311 does indeed change your deadkey, you can choose how much deadkey you want by playing with the value of that resistor.
check to see if D502 is cut or removed. this is your AMC diode, and its better if you leave it in and just adjust RV501 for max modulation.
if D502 is gone, just replace it with a 1N4148/ 1N914 type silicon diode. (very common)
looks like lots of fun can be had with this little beauty!
on mine im going to experiment with an NPC mod and some schottky diode mods for the receiver.
good luck with yours,
LC
i recently picked one of these up at a garage sale for 2 dollars, but i havent even turned it on yet.
the audio chip is the KIA 7217 AP.
as for why your radio doesnt work, i always start out doing a full alignment on a radio. that way, you can see how far you get in the alignment before things start not looking right and you will know which area of the radio to begin looking at.
unsolder the final and driver leads from the board and do the diode test with your voltmeter to determine if they are good or not.
here is a link to the cbtricks site. there you will find the schems that you need.
Cobra 19 Plus
you will also find the factory service manual here. in it you will find all the voltages for the PLL so you can check if its working properly.
read through the whole manual, you will learn alot about this radio.
as for the supertune; dont worry about which diode they are talking about because you dont want to mess with that anyway.
they are referring to the anti-spiking diode whose job is to keep large voltage spikes from damaging the windings of the audio transformer.
even if you did jumper it, you would only gain about 1 watt, if that.
not worth the possible damage to the audio transformer, which will be hard to find a replacement for.
the resistor they are referring to is R311, which is a 3.3K ohm resistor.
jumpering this will increase the deadkey. this may be what you are looking for by replacing the final with the 1969, but if you plan to run an amplifier after the radio, you might not want the higher deadkey.
i would try just replacing the final with the 1969 and then just re-align the transmitter. see what that gets you before you move on to other mods.
if you find that R311 does indeed change your deadkey, you can choose how much deadkey you want by playing with the value of that resistor.
check to see if D502 is cut or removed. this is your AMC diode, and its better if you leave it in and just adjust RV501 for max modulation.
if D502 is gone, just replace it with a 1N4148/ 1N914 type silicon diode. (very common)
looks like lots of fun can be had with this little beauty!
on mine im going to experiment with an NPC mod and some schottky diode mods for the receiver.
good luck with yours,
LC
Cannon, thanks for the great info. I too am pretty excited about cracking the 19 open and playing around. I have a friend with a 19 Untra...said I can have it for parts. I believe the 19+ and Ultra have the same board so instead of messing with removing parts I may just put the Ultra board in the Plus' case; gotta see first. Let me know how that NPC goes. I have that dont in my Galaxy 959 and it made a night & day difference...would be cool to see how it would work out in a 19+. when you do it please give me the info so I can try it. thanks again
Hey LC, here's what I was able to fanagle this mroning. get my hands on a 19 Ultra yesterday which works. So--I swapped faces...put the 19+ face on the 19 Ultra, was easier than swapping audio IC's. I also put in the 1969 final. according to my meter I am at 100% modulation however i'm around 2-4 watts. which is ok cause i run a 1x4. havent heard my local friends so getting a detailed radio check will have to wait for this evening.