Cobra 2000 No rx audio or TX audio on am

[ExitThirteen]

Lift one side of the diode and see if that allows you to change channels. It won't hurt to have that diode lifted, as that's part of a Cobra service bulletin upgrade. Let us know how you get on.


~Cheers~

 

[fernan_01]

so i lifted the diode and it wouldn't let me change channels or freq. but it did changed from 27.531 to 26.985..and still no ssb tx.

 

[unit_399]

Fernan -

Can you show or tell us where on the schematic the two points that you shorted together are ?? thanks

 

[ExitThirteen]

Ok, remove TR13, and check that transistor. it's labelled A733. If that transistor has gone fault, you'll also want to replace TR12, labelled C945. They are both located in the front right corner of the board, just left of VR3. Let us know how you get on.


~Cheers~

 

[fernan_01]

so in the diagram i couldnt find either the diode or jp4 & jp5 so i had to draw them..

 

[fernan_01]

ok checked tr12, 13, 35 & d43 and they are good... i will keep looking at the diagram to see if theres anything i can check... By the Way thank you guys so much for helping me.. im not going to give up on this.. Thanks

 

[fernan_01]

Should i be seeing any voltages on tr53?? i was testing for vltage and i get around 8v on tr47 but no voltages on tr53

 

[unit_399]

All of the pictures you posted won't load for me. I need to see the pic with the redline showing what you shorted.

 

[15minigrass]

FERNAN 01-


Check C174, 175, 179, and 181 for shorted/leaky. My guess is that it's C179. If it's bad, replace it with an electrolytic cap, not a tantalum. Good luck & 73s.

-399

if i was to replace C179, what size would i replace it with? 22uf 16v?

 

[Robb]

Yep; that should work OK.