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Question about RCA RP3721 Clock Radio

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RCA alarm clock - RP3721 - crystal or AC for time?

What does this alarm clock use to keep time? Is it primarily a waveshaping circuit off of the 60hz AC that clocks digital circuit - or - does it run always off of a crystal time keeping circuit? I assume for battery backup, it has a crystal time keeping circuit. If it does use 60hz AC, how does it switch when power may be detected as low? The problem is that every once and a while the clock gains time, but no AC has been lost (as far as observed). Thanks. Larry Park

Posted by Larry Park on

  • chrisalberts Jan 14, 2008

    my clock has run steadily for years, but suddenly started gaining 10 minutes a day. Could a dead battery cause this?

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They used to use crystals to help the timer ics to keep time but since the development of Micropros. all this is built in to one chip. Now they will use a resonator or a small crystal for the timing clock of the micro but nowdays the manufacture uses that clock to keep all in check. If your gaining time you probably are having problems with your ac duty cycle as this also keeps clocks in check.. This would not affect most devices but could be a problem. But of course a defective Micro could also cause this gain in time And probably is?? Now a battery backup is nothing more then a battery in line with the Microproccesors B+ terminal through of course a diode as well as a voltage limiter resistor to take over the B+ when the units ac supply is absent..

Posted on Mar 24, 2006

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Related Questions:

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1answer

Losses Time

what frequency does Jordon use on their power is it 50 hz are the clocks 60 Hz designed power usage.
may need a device to convert 50hz to 60hz
search google for
50 hz to 60hz frequency converter
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User manual

You can download the manual at this link;
http://www.manualowl.com/p/RCA/RP3721/Manual/54944
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User manual alarm

You can download the user manual at this link;

http://www.manualowl.com/p/RCA/RP3721/Manual/54944
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The alarm display in the lower right corner on model #RC40-A keeps blinking and will not stop. This happens with both wake 1 and wake 2 options. I fixed it once by unplugging the unit but it this did not...

Hello
Just reinstall the battries and adjust the time once again.

Battery back-up operation

* This clock radio is equipped with

a memory holding system that can

be powered with 2 "AA" batteries

(included). The power failure

protection circuit will not operate

unless battery is installed.

* When normal household power

is interrupted, or AC line cord

is unplugged, the batteries will

power the clock radio to keep

track of time and alarm settings

programmed into memory.

* When the battery backup functions,

the digital display will not light,

however, the function of alarm

still occurs during the power

interruption if remaining battery

power is adequate.

* Normal operation will resume after

AC power is restored so you will not
have to reset the time or the alarm

To install batteries:

1* Remove battery compartment door

(located at the bottom of the radio)

by applying thumb pressure to the

tab on battery door and then lift
the door out and off the cabinet

2* Insert 2 AA batteries (included).
3* Replace the compartment door

Replace batteries every year.

Power is fed to the unit even

when it is not functioning. To

cut the power supply off, the
power cable must be unplugged
OK.

0helpful
1answer

Can you daisy link two inverters together positive to positive neg to neg ac out to increase the watts


This will cause big problems. It will not work and will likely cause both inverters to fail. Power inverters must create the 60Hz sign wave from a crystal controlled internal frequency driver. It's like a clock that keeps the timing at 60Hz. 2 independent units will have slightly different clocks both in time and frequency. This would cause the output waveform of one unit to be out of phase with the second. If they are out of phase, they will look like loads to each other and likely fail. It would be possible if the inverters had a way to link their clocks or use only one clock. This could be designed in however I have never seen this feature. You can hook up multiple inverters to the low voltage side (12VDC), just don't hookup their 120VAC output side. Hope this helps.

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1answer

RCA RP5435B SN.1A006J255A0594-Clock running slow

Most of the Radio clocks by RCA are meant to be used with 60Hz AC line. This problem will not go away unles you can get a custom built 60 Hz AC power supply, may prove to be too expensive for the clock.
2helpful
1answer

Snooze timer

Well, unfortunately the snooze period is apparently preset on the RP3721 and cannot be changed.  The user's guide says that it is approximately 9 minutes long.  
9helpful
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Setting a Radio Station for Wake Up

You can download the manual from the link below: http://157.254.235.130/public/RP3721%20EN.pdf Please update the question & let us know if the information given was useful to you - Good Luck!
4helpful
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RCA RP3721 Alarm won't shut off

To turn alarm off completely, press WAKE1 and WAKE2 until the bell-shaped indicators go off.  
As for resetting the alarm (buzzer), press SET WAKE/CLOCK untill SET and WAKE! light.  Press left- or right+ arrow to set time.  Press WAKE1 until bell-shaped indicator comes on.  
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