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cobra 2000 gtl
- Thread starter kaos513
- Start date
I’d second that. The clock has to get its power without the switch, and the switch would function on both ac/dc.
I suggest trying an external DC supply to the DC jack on the rear, with the switch in the "DC" position.
If it works, you have AC power-supply trouble. The clock is powered from the unregulated side of the radio's AC supply. If the regulator pukes, the radio stays dark with the clock still working.
The power switch is a common failure, but it has two circuits. Only one of them is connected. A pair of jumper wires from the unused side to the side that's wired up may save you if that's what has gone bad.
This pic was meant to show the mike-socket modification, but the jumper wires on the power switch are visible, too.
And if the radio won't power up from the DC power cord, the switch may be the problem.
Remember that the power switch in this radio is not connected in the 'hot' side of the power to the radio. It interrupts the negative side of the DC-power source from the radio's main circuit board. The usual voltmeter tests will be confusing if you look for positive DC voltage on the Cobra 2000 power switch.
73
If it works, you have AC power-supply trouble. The clock is powered from the unregulated side of the radio's AC supply. If the regulator pukes, the radio stays dark with the clock still working.
The power switch is a common failure, but it has two circuits. Only one of them is connected. A pair of jumper wires from the unused side to the side that's wired up may save you if that's what has gone bad.
This pic was meant to show the mike-socket modification, but the jumper wires on the power switch are visible, too.
And if the radio won't power up from the DC power cord, the switch may be the problem.
Remember that the power switch in this radio is not connected in the 'hot' side of the power to the radio. It interrupts the negative side of the DC-power source from the radio's main circuit board. The usual voltmeter tests will be confusing if you look for positive DC voltage on the Cobra 2000 power switch.
73
Do I have to scrape the switch board on each side and attach jumper ?I suggest trying an external DC supply to the DC jack on the rear, with the switch in the "DC" position.
If it works, you have AC power-supply trouble. The clock is powered from the unregulated side of the radio's AC supply. If the regulator pukes, the radio stays dark with the clock still working.
The power switch is a common failure, but it has two circuits. Only one of them is connected. A pair of jumper wires from the unused side to the side that's wired up may save you if that's what has gone bad.
This pic was meant to show the mike-socket modification, but the jumper wires on the power switch are visible, too.
And if the radio won't power up from the DC power cord, the switch may be the problem.
Remember that the power switch in this radio is not connected in the 'hot' side of the power to the radio. It interrupts the negative side of the DC-power source from the radio's main circuit board. The usual voltmeter tests will be confusing if you look for positive DC voltage on the Cobra 2000 power switch.
73
before you do that, push the power button in with the radio connected to a power source, either AC or DC, and check the DC voltage at pin 2 of the MB3756 voltage regulator.
you should see 13.8 volts there if the clock is working.
now check the voltage at pin 1 of the voltage regulator (these are the pins that diode was across). my guess is that you will see no voltage here.
if you don't see the 8 volts DC at pin 1, then unsolder it from the board and check it again, checking the pin itself.
if you now see the 8 volts, then something on that PC board trace is shorted and pulling that voltage down to nothing.
if you still don't see the 8 volts on pin 1 with it away from the board, then your voltage regulator is probably bad and needs to be replaced.
don't just replace the regulator without testing the way i showed you, or you might blow the new one too.
LC
you should see 13.8 volts there if the clock is working.
now check the voltage at pin 1 of the voltage regulator (these are the pins that diode was across). my guess is that you will see no voltage here.
if you don't see the 8 volts DC at pin 1, then unsolder it from the board and check it again, checking the pin itself.
if you now see the 8 volts, then something on that PC board trace is shorted and pulling that voltage down to nothing.
if you still don't see the 8 volts on pin 1 with it away from the board, then your voltage regulator is probably bad and needs to be replaced.
don't just replace the regulator without testing the way i showed you, or you might blow the new one too.
LC