Question about RCA RP3721 Clock Radio

1 Answer

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 on

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 10 achievements.


    An expert that got 5 achievements.


    An expert whose answer got voted for 500 times.

  • Master
  • 3,130 Answers
Re: RCA alarm clock - RP3721 - crystal or AC for time?

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

Add Your Answer

0 characters

Uploading: 0%


Complete. Click "Add" to insert your video. Add


3 Points

Related Questions:

1 Answer

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

Apr 15, 2014 | Sanyo R-6800 2-IN-1 ALARM CLOCK AND RADIO...

1 Answer

User manual

You can download the manual at this link;

Sep 12, 2013 | RCA RP3721 Clock Radio

1 Answer

User manual alarm

You can download the user manual at this link;

Jun 20, 2013 | RCA RP3721 Clock Radio

1 Answer

I am not sure how to set the time interval in the nap mode. It starts at 2 hours, and I can't change it.

Ok, this is the way it works, and I keep my clock radio for this feature alone. It is a 2 hour "count down" timer. It is set in 15 minute intervals. Supposed you wanted to take a 1/2 hour nap. Press the button but don't let go. As you hold your finger down the timer will start at 2 hours (2.0) and it will then go to 1.45, etc. When you get to a 1/2 hour let go and it will start counting down. If, in the process, you make a mistake, press the blue button and don't let go. Hold it down until it erases the setting and removes the NAP text from the front display. Release button. Start holding down the button again. Once again, the display will go to two hours, continue to press button, it will start counting back in 15 minute increments. Again, when it gets to 1/2 hour, quickly let the button go. As the clock counts down, you cannot see how much time is left on the clock. Press the button, quickly let go again. It will display how much of the 1/2 is left. When the clock counts down to zero, either the alarm will sound or the radio will start playing depending on what you set the alarm to do. Press the off button, that's it... (0:

Sep 01, 2011 | RCA RP3721 Clock Radio

1 Answer

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...

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

Jul 10, 2011 | RCA Rc40 Clock Radio

2 Answers

Bose Wave Radio/CD clock running very slow. Now that I've moved it across the pacific ocean(US to NZ) the clock is suddenly running very slow, losing 10-15 minutes per hour while running on any...

My guess is that the clock in the radio is based off of the AC line frequency (not voltage). In the US the line frequency is 60hz (hertz). I'm guessing that the line frequency in NZ is 50hz, which would seem to explain that extreme amount of time loss. I would check with Bose, but I'm betting they make different 50hz models for export.

May 16, 2010 | Bose Wave Radio

1 Answer

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.

Sep 20, 2008 | RCA RP5430 Clock Radio

1 Answer

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.  

Feb 18, 2008 | RCA RP3721 Clock Radio

1 Answer

Setting a Radio Station for Wake Up

You can download the manual from the link below: Please update the question & let us know if the information given was useful to you - Good Luck!

Aug 30, 2007 | RCA RP3721 Clock Radio

1 Answer

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.  

Jun 14, 2007 | RCA RP3721 Clock Radio

Not finding what you are looking for?
RCA RP3721 Clock Radio Logo

Related Topics:

477 people viewed this question

Ask a Question

Usually answered in minutes!

Top RCA Clock Radios Experts

The Knight
The Knight

Level 3 Expert

66499 Answers

Cindy Wells

Level 3 Expert

4720 Answers

Gyula Lacz

Level 3 Expert

482 Answers

Are you a RCA Clock Radio Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides