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Uniden Washington no transmit

D

dieselburner

Member
Apr 25, 2011
23
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I decided to pull my old washington out and use it but I found that it no longer puts out a carrier on am or ssb. If I have a radio on next to it I can receive a faint signal from the washington. The receive side of the washington works fine. I bought a sams manual for it and worked my way through it and everything checks out fine until I get to the voltages for the rf driver 2sc1306. My base voltage is on this transistor is negative .32 volts. My collector is 5.6v which is in the ball park. The emitter is grounded which is correct. This is measured with a dead key on am. Any ideas on what the problem can be with this radio?
 
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Symptoms sounds like the final transistor to me.

I thought this radio had a 2sc2166 driver.
Does it have a 2sc1969 final?
Sounds like someone modded the output - as a guess . . .
Has it?
 
The stock final is a 2sc1969 and the stock driver is a 2sc1306. I replaced the final and the 2Sc1306 and there was no change. I was able to find an original 1306 but had to use a CB-20 for the final. Since that was not the problem, I saved my old parts. I am now thinking it's something related to the driver. This radio was peaked out by a shop years ago but it has worked fine until now.
 
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Attached schematic is for the Cobra 142GTL, which is the same basic radio. I am no tech; but if you can follow the 8v TX supply from the source regulator thru the TX circuit you might find where the voltage stops. A guess would say that it is somewhere between the driver and the final. Did you check the voltage at the driver and final on TX?

Here is the CBTricks page for the radio:
Cobra 142GTL
 

Attachments

  • cobra_142gtl_main_sch_a_size.pdf
    1.3 MB · Views: 54
Thanks Robb, I have the sams manual and went through it but could not pin point the problem. I am still staring at the schematic trying to figure it out but I think I am in over my head here...
 
Since it hasn't been taken out and used for a long period of time; the electrolytic caps would/should be the first suspects. Probably a dried out cap or two. Using the schematic; you may try to replace all of them in that circuit before you consider shipping it off to a tech.

God Bless/73 . . .
 
Well, I won't be sending it out to be fixed. I will keep on trying to fix it myself. I was hoping that somebody on here would read this and say "dang, that just happened to my radio last week and here's what I did to fix it" or something like that. Anyone know what the diodes up above the final and driver transistors are for? They are mounted to the heat sink also.
 
Hello; I believe they are varistors, that change resistance as temperature changes to prevent damage to the driver and final,and i agree if your voltages are correct and driver and final are ok and radio has been in storage it's probably an electrolytic cap gone south. Regards warlock35po
 

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