Cobra 2000GTL, clock but no power on.

[robinz]

loosecannon,

I have one question for you regarding your recommendation of changing C181 to 1000 uF from the stock value of 10 uF. That's a significant increase.

I see it is located next to the TA7222AP Audio Amplifier. What is the expected result of the increased value?

 

[loosecannon]

C181 is connected across the main 13.8 volt line coming in to the audio amp.

increasing its value provides better filtering.

yes, by increasing C172 to a 2200, you are doing essentially the same thing, i just do it anyway as it cant hurt.

look at the schematic and you will see what i mean.

LC

 

[robinz]

Thanks for your clarification. I looked at the schematic but I was not familiar with the pin outs of the TA7222AP. I used a 3300 uF for C172, a value that was discovered somewhere else. I'll proceed with your other recommendations.

 

[loosecannon]

just a little tidbit here.

i have never liked the muting of the audio while changing channels.
i like to be able to "scan the band" by flipping through the channels about 1 second at time without having the audio muted each time i turn the channel knob.

if you want to get rid of the muting, just remove C232. no replacement.
easy at that.
LC

 

[robinz]

>> ... just remove C232.

That for that tidbit, I have not come across that one before. I'll think about it.

 

[robinz]

Status Update:

System Update:

Just finished replacing all the electrolytics. I have a better appreciation for the tech's & businesses that do this ($$$). I'm putting together a re-capping kit that will have all the locations identified and differences discovered from the service manual + the mystery cap I discovered (factory). I will have it on eBay by the end of next week. Look for "electrolytic capacitor kit for cobra 2000"

>> ... be good to go for another 20+ years.
>> ... of course the problem is that it takes a fair amount of time to re-cap a radio and im not sure anyone would want to pay for that.

I will go through a basic PLL/RX/TX alignment before I move on to the next phase, installing SCHOTTKY diodes, widebanding, and ...
>> ... dont forget to change TR41 on the main PC board, and TR301 on the power supply board to a 2N6487 or NTE152

Thanks ALL for your input.

 

[Klondike Mike]

>> ... dont forget to change TR41 on the main PC board, and TR301 on the power supply board to a 2N6487 or NTE152.

Correction Notice: The NTE cross reference for the 2n6487 is NTE331.

 

[loosecannon]

any of them will work just fine.

the 2N6487 is actually overkill for what the part needs to do, its just an easy part to find.
LC

 

[Klondike Mike]

any of them will work just fine.
LC

Oh, I thought the NTE number was an equivalent and not an "or". Thanks.