RCA Clock radio wierd problem - Help!

[Rusty]

I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time. Never loses time. What I mean is
that it might run fine for 15 hours with the time right on to the
second and then boom, it gains a random amount of time. It might only
be 1 hour or 24+ hours before it happens. Today it kept the right time
for about 6 hours and then it gained 4 minutes. Then for the next 8
hours it kept that 4 minute difference and checking it just now, it
gained another 2 minutes.

This is NOT an isolated incident. This is a brand new unit. In fact it
is the EIGHTH unit with this problem. I have two of them(both brand
new) set up next to each other and BOTH are doing the same thing. The
others had the problem with most with worst time problems. The first 5
were from Walmart. Well, they don't carry it anymore. The next 3 were
from Sears and now they are out of them. I didn't buy them all at the
same time. I just kept exchanging them. It was about the 4th or 5th
one before I started tracking the date codes and have had a wide
variety of codes.

Any ideas on a fix?

 

[Jerry G.]

You should get another make of unit. This manufacture in their TV sets, as
well as many of their other types of electronics has problems in some of
their models. I would have switched makes, and or to a completely different
model to try, after the second one!

GE, and a few others have some models that get their time from the NIST.
This means that you just have to set it close for the time, and after 24
hours, it would keep itself adjusted as long as it can get the signal. Just
make sure it is set for the proper time zone to start with. I have a few of
these clocks around our home, and they never go off time!

--

Jerry G.
==========================


I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time. Never loses time. What I mean is
that it might run fine for 15 hours with the time right on to the
second and then boom, it gains a random amount of time. It might only
be 1 hour or 24+ hours before it happens. Today it kept the right time
for about 6 hours and then it gained 4 minutes. Then for the next 8
hours it kept that 4 minute difference and checking it just now, it
gained another 2 minutes.

This is NOT an isolated incident. This is a brand new unit. In fact it
is the EIGHTH unit with this problem. I have two of them(both brand
new) set up next to each other and BOTH are doing the same thing. The
others had the problem with most with worst time problems. The first 5
were from Walmart. Well, they don't carry it anymore. The next 3 were
from Sears and now they are out of them. I didn't buy them all at the
same time. I just kept exchanging them. It was about the 4th or 5th
one before I started tracking the date codes and have had a wide
variety of codes.

Any ideas on a fix?

 

[Sam Goldwasser]

He says this happens with several different brands of clock radios if
I understand the post correctly. In that case, look to noise on the
power line or some other similar external cause.

If they all are the same model, then I agree, it's junk.

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[Ken G.]

Buy an older radio that works from a thrift shop .

 

[Michael A. Covington]

Are they keeping time by counting the 60 Hz cycles of your AC power?

And do you have some unusual kind of noise on the power lines?

See if they keep time correctly in your office, or in someone else's home.

 

[[email protected]]

I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time. Never loses time. What I mean is
that it might run fine for 15 hours with the time right on to the
second and then boom, it gains a random amount of time. It might only
be 1 hour or 24+ hours before it happens. Today it kept the right time
for about 6 hours and then it gained 4 minutes. Then for the next 8
hours it kept that 4 minute difference and checking it just now, it
gained another 2 minutes.

snip

I have a Magnavox clock radio with battery backup. Every time I lose
power to the house, the clock radio gains between 3-5 minutes. I don't
know if this info helps at all.

 

[Michael A. Covington]

I have a Magnavox clock radio with battery backup. Every time I lose
power to the house, the clock radio gains between 3-5 minutes. I don't
know if this info helps at all.

That is extremely relevant. Do his problems coincide with brief power
outages?

 

[Rusty]

I do not have any power outages nor brownouts. No other electronic
equipment in the house is affected. The problem occurs with or without
a backup battery.

I know some replies said junk, try another model and such. That is not
the key here. I am curious as hell and am trying to figure it out.

 

[Rusty]

On quick inspection, it appears to be crystal controlled. I got as far
as opening it up and will start troubleshooting tomorrow. I have
checked my house power and it appears to be clean. That is not to say
something appears on the line randomly but without any way to capture
that event, I can't sit in front of my oscope hoping to see it.

Now if I could find the schematics for this I would be set.

 

[Rusty]

Only this model clock radio. No other clocks of any sort in the house
is affected in this way.

 

[Franc Zabkar]

I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time. Never loses time. What I mean is
that it might run fine for 15 hours with the time right on to the
second and then boom, it gains a random amount of time. It might only
be 1 hour or 24+ hours before it happens. Today it kept the right time
for about 6 hours and then it gained 4 minutes. Then for the next 8
hours it kept that 4 minute difference and checking it just now, it
gained another 2 minutes.

This is NOT an isolated incident. This is a brand new unit. In fact it
is the EIGHTH unit with this problem. I have two of them(both brand
new) set up next to each other and BOTH are doing the same thing. The
others had the problem with most with worst time problems. The first 5
were from Walmart. Well, they don't carry it anymore. The next 3 were
from Sears and now they are out of them. I didn't buy them all at the
same time. I just kept exchanging them. It was about the 4th or 5th
one before I started tracking the date codes and have had a wide
variety of codes.

Any ideas on a fix?

Is the clock reacting to the offpeak switching signals from your
electricity supplier?


- Franc Zabkar

 

[Franc Zabkar]

I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time.

Which chip does it use? Maybe the application circuit in the datasheet
will tell us something.


- Franc Zabkar

 

[Franc Zabkar]

I recently bought the RCA RP3710A Alarm Clock radio. The problem with
it is that it randomly gains time. Never loses time.

Apparently you're not the only one with this problem:
http://electronics.kewler.net/rca-r...-lcd-digital-tune-dual-wake_B00008UVAG_i.html


- Franc Zabkar

 

[Sam Goldwasser]

Only this model clock radio. No other clocks of any sort in the house
is affected in this way.

So, out of curiosity, if you have been having problems with this model,
why have you puchased 8 of them?

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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[Bill Jeffrey]

I was reading about this somewhere just the other day - I think it was
rec.antiques.radio+phono, but I will confirm and get back if that is wrong.

The topic of the thread was remote-reading electrical power meters - you
could Google it. The gist of the topic was that there are many ways in
which a remote-reading power meter can work. Most cause no harm or
interference of any kind. But one of them involves "modulating the
zero-crossings" in the AC waveform, a signalling method which can be
triggered and read from a remote location. Apparently, this technique
can cause extra zero-crossings to show up, and a clock which counts time
by counting zero-crossings will gain time. There is any easy fix, IIRC.

So the question becomes, has the power company retrofitted the power
meters in your neighborhood recently?

Bill

 

[Sam Goldwasser]

I was reading about this somewhere just the other day - I think it was
rec.antiques.radio+phono, but I will confirm and get back if that is
wrong.

The topic of the thread was remote-reading electrical power meters -
you could Google it. The gist of the topic was that there are many
ways in which a remote-reading power meter can work. Most cause no
harm or interference of any kind. But one of them involves
"modulating the zero-crossings" in the AC waveform, a signalling
method which can be triggered and read from a remote location.
Apparently, this technique can cause extra zero-crossings to show up,
and a clock which counts time by counting zero-crossings will gain
time. There is any easy fix, IIRC.

So the question becomes, has the power company retrofitted the power
meters in your neighborhood recently?

I'm glad my semi-antique (30+ years) clock radio still uses a synchronouc
motor. Full cycles are all that matter!

How did a signally scheme like that ever get approved? A large precentage
of AC powered clocks must count zero crossings.

But, didn't he say he thought there was a crystal in the RCA?

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Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the feedback form on the S.E.R FAQ Web sites.

 

[Bill Jeffrey]

Bill Jeffrey writes:

I'm glad my semi-antique (30+ years) clock radio still uses a synchronouc
motor. Full cycles are all that matter!

Yup. But they are gettign harder to find. Electronics is cheep!

How did a signally scheme like that ever get approved? A large precentage
of AC powered clocks must count zero crossings.

Actually, the post that I read may have been referring to the signalling
scheme used by the X-10 products - a short burst of 120KHz at the zero
crossing. IIRC, the "easy fix" was to add a 0.001 cap across the clock
circuit, which would probably reduce the level of 120 KHz to an
insignificant level. Haven't yet found the post I am referring to, but
there wasn't much more than that.

But, didn't he say he thought there was a crystal in the RCA?

Yes, he did. I assume that the crystal oscillator is there simply to
take over in the event of power failure. For "normal" operation, the
power line frequency (or at least aggregate number of cycles over 24
hours) is much more accurate than any cheap crystal oscillator.

So the next question for the OP is, have you recently installed any X-10
equipment?

Bill

 

[Franc Zabkar]

Sam Goldwasser wrote:

Yes, he did. I assume that the crystal oscillator is there simply to
take over in the event of power failure. For "normal" operation, the
power line frequency (or at least aggregate number of cycles over 24
hours) is much more accurate than any cheap crystal oscillator.

I suspect the crystal also provides the clocking for the uP (?) and
LCD. AFAIK, a uP can't get much work done at 50 or 60Hz


- Franc Zabkar

 

[Rusty]

I don't know yet but I will check that out.

Thanks

 

[Jim Adney]

Do they both do it at the same time?

If so, my guess is that there is some noise on your line occasionally
which fools the clocks into counting them as extra cycles. It might be
possible to add a filter to the input that would only pass thru
frequencies near 60 Hz, but I'm afraid that such a filter would
probably be rather large.

-