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Cobra 25 ltd newer version parts help
- Thread starter dss56
- Start date
The pa is there but audio is low like transmitting. I have used my audio tracer and dont have the correct schematic but I have a cobra 29 with this same chip. Im going to see if the circuit is built the same and try from there and see if a part is bad.
It seems that the audio is not amplified from the tda2003 and then routed to the final to modulate out with the final. Im sure the audio chip is ok as there is good receive audio and very low low out audio.
Andy thanks for all your help upto now
It seems that the audio is not amplified from the tda2003 and then routed to the final to modulate out with the final. Im sure the audio chip is ok as there is good receive audio and very low low out audio.
Andy thanks for all your help upto now
Yet no PA, ok, so how is the switch wiring on panel - any loose wire or shoddy soldering?
Cold soldering joints come to mind...
We may have to start looking into Mic amp section - the C70 thing was to make sure it was NOT feeding current back into the Mic amp - can do that all the time even for PA - so the PA problem may indicate Mic amp routing to the Audio Amp - you may have failed parts or bad soldering of them in line from mic amp that are doing this.
Locate the Mic amp section, there is a wire that goes to the Mic jack from here - by a part possibly called C90 and another C148 - follow that wire back to the harness - should go to pin 3.
Now, to see if the Mic amp works, PA or TX - Pull, unsolder C94 - see if that changes your audio from weak to too loud...
Cold soldering joints come to mind...
We may have to start looking into Mic amp section - the C70 thing was to make sure it was NOT feeding current back into the Mic amp - can do that all the time even for PA - so the PA problem may indicate Mic amp routing to the Audio Amp - you may have failed parts or bad soldering of them in line from mic amp that are doing this.
Locate the Mic amp section, there is a wire that goes to the Mic jack from here - by a part possibly called C90 and another C148 - follow that wire back to the harness - should go to pin 3.
Now, to see if the Mic amp works, PA or TX - Pull, unsolder C94 - see if that changes your audio from weak to too loud...
I checked all the wires that go to the pc board and all looked good no bad solder Joints.
This radio was shorted out by the customer and took out the tx and receive. I have replaced the pll from another radio and the final. But ended up with this audio problem.
I will find c94 and remove and see what happens
This radio was shorted out by the customer and took out the tx and receive. I have replaced the pll from another radio and the final. But ended up with this audio problem.
I will find c94 and remove and see what happens
By audio amp near front mic socket by meter. Along that side.
Ok now knowing this - the short can take out a regulator - like TR17.
So pay attention to the SQUELCH controls operation too.
If the regulator is damaged - Squelch would be affected as well as meter lamp brightness
Ok now knowing this - the short can take out a regulator - like TR17.
So pay attention to the SQUELCH controls operation too.
If the regulator is damaged - Squelch would be affected as well as meter lamp brightness
Gosh, did the kid blow up the Mic Gain pot on the front panel?
Is Mic gain even adjustable?
That requires a test leads to DVM check - sort of thing...
Now if Mic gain shorted out - you have to look around that front corner mess to see if they did some damage there...
Review this, this is from a PC68 - but it may help you locate the parts and the areas needing attention...
Hope this can help you understand that front panel...
Is Mic gain even adjustable?
That requires a test leads to DVM check - sort of thing...
Now if Mic gain shorted out - you have to look around that front corner mess to see if they did some damage there...
Review this, this is from a PC68 - but it may help you locate the parts and the areas needing attention...
Hope this can help you understand that front panel...
I will check the mike gain with meter I just had to get my 4yr old grand son from
daycare. SO i will try in about 2 hours.
the vr5 has no change in power moving it or the modulation control.
I will try the front gain control and see I will jump across for wide open and see what happens I will also put my fluke meter on it.
I appreciate all the help it motivates me as I gave up earlier this morning
daycare. SO i will try in about 2 hours.
the vr5 has no change in power moving it or the modulation control.
I will try the front gain control and see I will jump across for wide open and see what happens I will also put my fluke meter on it.
I appreciate all the help it motivates me as I gave up earlier this morning
I can only hope you can get thru this, I'm working right along side ya'.
Gotta take care of some chores myself...
Step away for a moment or two, get your head around it, you'll be fine. Take a break for now...
Regards!
Gotta take care of some chores myself...
Step away for a moment or two, get your head around it, you'll be fine. Take a break for now...
Regards!
Everything else works on radio but the low out modulation.
The radio will only peak out to about 3 watts out wondering if the pre driver for the final is bad?
Well, that would be obvious - but you said PA was low too...
Is it still?
That's why I mentioned the Squelch control - for if it took out the Pre-driver - that can explain a whole bunch...for the Pre driver can't supply enough power.
Is it still?
That's why I mentioned the Squelch control - for if it took out the Pre-driver - that can explain a whole bunch...for the Pre driver can't supply enough power.
The squelch works ok i have tried looking at the schematic to see if something else could cause this Im baffled. So tomorrow Im going to swap out the final and pre-driver to see if it will help. Never had this problem before usually the audio chip or final but I replaced both with know good parts that worked in another radio.
It seems something is either draining the audio to the audio chip and then to the final and the predriver is inline.
The radio does not tune with power too good like I said about 3 watts peak using the 2sc2078.
And all your suggestions today and what i have tried Im baffled
It seems something is either draining the audio to the audio chip and then to the final and the predriver is inline.
The radio does not tune with power too good like I said about 3 watts peak using the 2sc2078.
And all your suggestions today and what i have tried Im baffled
- No one is chatting at the moment.
