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Cobra 148 GTL Not powering up.
- Thread starter American-Vulture
- Start date
Not weird at all. It's an audio equalizer that was hacked out of it's case. That it's inside of a 148 is kinda strange.
Now to find out if it was in the mic or speaker line.
While you're at it look on the main board of the radio for identifying numbers/letters.
We still need to know which generation of radio it is.
Now to find out if it was in the mic or speaker line.
While you're at it look on the main board of the radio for identifying numbers/letters.
We still need to know which generation of radio it is.
PLL?
Huh?
Where?
I see a MN3207 part made by Matsushita/Panasonic that's listed as a 1024-stage bucket-brigade chip. It's used for analog signal delay and reverb.
The other chips are dual op-amps, typical for a reverb/echo circuit.
It looks for all the world like a reverb box sold by RatShack 15 or 20-plus years ago. Drivers wanted them modded with a 4-pin mike socket and plug to use with their radios. Just couldn't run any power with one of those. Too easy to bleed.
The info for the MN3207 can be found at http://www.alldatasheet.com. You'll have to type the number into the search box yourself. They don't permit external links to their files.
73
Huh?
Where?
I see a MN3207 part made by Matsushita/Panasonic that's listed as a 1024-stage bucket-brigade chip. It's used for analog signal delay and reverb.
The other chips are dual op-amps, typical for a reverb/echo circuit.
It looks for all the world like a reverb box sold by RatShack 15 or 20-plus years ago. Drivers wanted them modded with a 4-pin mike socket and plug to use with their radios. Just couldn't run any power with one of those. Too easy to bleed.
The info for the MN3207 can be found at http://www.alldatasheet.com. You'll have to type the number into the search box yourself. They don't permit external links to their files.
73
so you get 13.8 volts at the power jack, but not at pin 2 of the MB3756 voltage regulator? (this is the IC mounted more toward the front of the radio on that wall)
keep that audio board out of the radio for now and let's see if we can get it working without it.
Being that this is the newer ranger style 148 board, there is a mod that gets done to all of them that pass through repair shops that has to do with this section of the radio.
there is a chance that someone did this mod wrong, or got halfway through it, or tried to remove it, or...
and it could cause there to be a break in your 13.8 volt line coming in to the radio.
In the old 148 boards, they go right from the power switch to pin 2 of the MB3756, and then branch off to T1, and then to the audio chip and other VCC connections.
in the ranger style boards, they go through T1 first, before going to the voltage reg, and those small wires can cause warble on SSB modulation peaks and other such maladies.
the mod is to cut a trace, and add a jumper back in to the PC board so that pin 2 of the MB3756 gets powered before T1.
check this section of the radio and see where you lose the 13.8 volts.
it might be as simple as someone splicing in to the line that goes to the power switch in order to power that audio board, and you just need to re-connect that wire.
do you have a schematic to look at?
LC
keep that audio board out of the radio for now and let's see if we can get it working without it.
Being that this is the newer ranger style 148 board, there is a mod that gets done to all of them that pass through repair shops that has to do with this section of the radio.
there is a chance that someone did this mod wrong, or got halfway through it, or tried to remove it, or...
and it could cause there to be a break in your 13.8 volt line coming in to the radio.
In the old 148 boards, they go right from the power switch to pin 2 of the MB3756, and then branch off to T1, and then to the audio chip and other VCC connections.
in the ranger style boards, they go through T1 first, before going to the voltage reg, and those small wires can cause warble on SSB modulation peaks and other such maladies.
the mod is to cut a trace, and add a jumper back in to the PC board so that pin 2 of the MB3756 gets powered before T1.
check this section of the radio and see where you lose the 13.8 volts.
it might be as simple as someone splicing in to the line that goes to the power switch in order to power that audio board, and you just need to re-connect that wire.
do you have a schematic to look at?
LC
Yes I do.Theres some other stuff hacked .Trying to return it to back into DR Jeckle.