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Cobra 2000 non serious problem
- Thread starter TonyV225
- Start date
That's simple. Your "Dynalert" is broke.
That's Cobra-speak for the alarm-clock function that turns on the radio instead of the alarm.
There's an SCR in the counter module that's gone bad, and prevents the power switch from shutting things down all the way.
Simplest fix is to find the 4-pin plug at the rear of the counter module, marked J409. The brown wire should lead over to the power switch. Cut that one, and the radio should turn off all the way again.
If you want the Dynalert to work, you'll need a replacement for the SCR, and the nerve to take the counter module apart.
73
That's Cobra-speak for the alarm-clock function that turns on the radio instead of the alarm.
There's an SCR in the counter module that's gone bad, and prevents the power switch from shutting things down all the way.
Simplest fix is to find the 4-pin plug at the rear of the counter module, marked J409. The brown wire should lead over to the power switch. Cut that one, and the radio should turn off all the way again.
If you want the Dynalert to work, you'll need a replacement for the SCR, and the nerve to take the counter module apart.
73
Not to disagree w/Nomad here,but I had one do that and it turned out to be one of the bulbs was burnt out.I don't remember which one now,but I replaced that particular bulb,and
it was fine after that.Still is as a matter of fact.It would sure be nice if it were that simple anyway! If you've got a spare
2000,just unplug the counter module and remove the four screws underside of the module and try it in place of the
suspicious one.Who knows,it may work just great! Good luck.
Nomad,what is a SCR component? Silicone resistor?
You lost me there;never heard that term before now!
Thanks.Slim CDX285
it was fine after that.Still is as a matter of fact.It would sure be nice if it were that simple anyway! If you've got a spare
2000,just unplug the counter module and remove the four screws underside of the module and try it in place of the
suspicious one.Who knows,it may work just great! Good luck.
Nomad,what is a SCR component? Silicone resistor?
You lost me there;never heard that term before now!
Thanks.Slim CDX285
Hi Slim,
A SCR is a Silicon Controlled Rectifier. Built kinda like a 3-terminal transistor, but with a difference.
The two main terminals are marked "anode" and "cathode", like a rectifier diode. Difference is, it won't turn "on" when the polarity has positive on the anode. The third leg is called the "gate". Feed a small current into the gate, and now it turns on, and acts like a normal diode on the other two legs. The difference between a SCR and a transistor is that when you take away the current from the gate on a SCR, it stays on. A transistor has to have "drive" current into that third leg to keep it on. A SCR will stay on until you shut off the current to it. In the 2000, pushing in the power switch will turn off the "wake to radio", next time the power switch gets pushed.
I guess they did it this way so that the alarm clock chip would only need to 'trigger' the radio to turn on once, and stay on until you turn it off. Otherwise, the radio would turn on and off with each "beep" from the alarm. A clever setup, NEVER used in ANY other base radio I ever saw, made before or since.
BTW, the one other place you'll find a SCR is in high-quality DC power supplies, like Tripp-Lite and Astron. A SCR is used for the over-voltage "crowbar" protector. If the output of the power supply rises above the 16-Volt (usually) trip point (even briefly), the SCR places a dead short across the plus and minus terminals inside the supply. In theory, this trips the current overload protection, and prevents anything over 16 Volts from reaching your equipment. The only way to reset it is to turn the AC switch off, then back on once the filter caps discharge.
The cheaper Euro/Pyramid/Samlex power supplies have no such feature in them.
73
A SCR is a Silicon Controlled Rectifier. Built kinda like a 3-terminal transistor, but with a difference.
The two main terminals are marked "anode" and "cathode", like a rectifier diode. Difference is, it won't turn "on" when the polarity has positive on the anode. The third leg is called the "gate". Feed a small current into the gate, and now it turns on, and acts like a normal diode on the other two legs. The difference between a SCR and a transistor is that when you take away the current from the gate on a SCR, it stays on. A transistor has to have "drive" current into that third leg to keep it on. A SCR will stay on until you shut off the current to it. In the 2000, pushing in the power switch will turn off the "wake to radio", next time the power switch gets pushed.
I guess they did it this way so that the alarm clock chip would only need to 'trigger' the radio to turn on once, and stay on until you turn it off. Otherwise, the radio would turn on and off with each "beep" from the alarm. A clever setup, NEVER used in ANY other base radio I ever saw, made before or since.
BTW, the one other place you'll find a SCR is in high-quality DC power supplies, like Tripp-Lite and Astron. A SCR is used for the over-voltage "crowbar" protector. If the output of the power supply rises above the 16-Volt (usually) trip point (even briefly), the SCR places a dead short across the plus and minus terminals inside the supply. In theory, this trips the current overload protection, and prevents anything over 16 Volts from reaching your equipment. The only way to reset it is to turn the AC switch off, then back on once the filter caps discharge.
The cheaper Euro/Pyramid/Samlex power supplies have no such feature in them.
73