Got a Cobra 29 LTD Classic Chrome Edition on the desk at the moment.
Issue:
No power (DC)
Evaluation:
1. Diode was blown in DC line and trace burnt in half in same area.
2. Some type of audio derived mod.
After fixing the power in issue, I contacted the owner and asked what he wanted done to it other than just fixing the DC side. He said he wants that strange mod removed and my variable key installed, and then a complete alignment.
Well, There was a variable resistor tied from JP31 over to ground (case of L21) and a resistor tied to the VR going to the rear hole of R56 with a 1k resistor in series.
The radio receives and transmits fine. Transmit is around 3w and swings to around 40w PEP.
I removed that mod and installed the variable key using a tip120 the way I do on all 29s and ended up with only a 1/2w deadkey at most and swings to 30w. I've tried adding a 33pf to 68pf to C62 to increase the key, but it barely comes up to around 3/4w key. I removed the variable key completely and put everything back the way it should be, and still only 3/4w key swinging to a tad over 30w.
Question is, what all gets changed when using the audio derived mod in a Cobra 29 so I can reverse everything that was done for that mod so I can install my variable and it works like it should?
I've seen a post somewhere before on this site that Handy Andy posted with that mod. It comes from JP31 up to a variable resistor that is tied to ground (L21) and also goes through a 1k ohm resistor back to the rear hole of R56.
Issue:
No power (DC)
Evaluation:
1. Diode was blown in DC line and trace burnt in half in same area.
2. Some type of audio derived mod.
After fixing the power in issue, I contacted the owner and asked what he wanted done to it other than just fixing the DC side. He said he wants that strange mod removed and my variable key installed, and then a complete alignment.
Well, There was a variable resistor tied from JP31 over to ground (case of L21) and a resistor tied to the VR going to the rear hole of R56 with a 1k resistor in series.
The radio receives and transmits fine. Transmit is around 3w and swings to around 40w PEP.
I removed that mod and installed the variable key using a tip120 the way I do on all 29s and ended up with only a 1/2w deadkey at most and swings to 30w. I've tried adding a 33pf to 68pf to C62 to increase the key, but it barely comes up to around 3/4w key. I removed the variable key completely and put everything back the way it should be, and still only 3/4w key swinging to a tad over 30w.
Question is, what all gets changed when using the audio derived mod in a Cobra 29 so I can reverse everything that was done for that mod so I can install my variable and it works like it should?
I've seen a post somewhere before on this site that Handy Andy posted with that mod. It comes from JP31 up to a variable resistor that is tied to ground (L21) and also goes through a 1k ohm resistor back to the rear hole of R56.
