Author Topic: Alarm clock very low sound  (Read 2975 times)
Cole D.
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Alarm clock very low sound « on: March 07, 2020, 02:02:07 PM » Author: Cole D.
I have 2006 year RCA alarm clock radio. It works fine except the speaker for the radio. It's very quiet, even all the way up. I can hear the radio if I put my ear on the speaker but just barely. I tried different stations and uncurling the cord/antenna and it's the same.

Could it be loose connection or bad soldering? Or maybe a bad resistor?
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Ash
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Re: Alarm clock very low sound « Reply #1 on: March 07, 2020, 04:27:13 PM » Author: Ash
Could be bad connections (also in places such as the volume pot or bypass contact in the headphones jack), dry capacitors (especially whats in series with the speaker at the amp output), damaged speaker, and some other things

Resistors dont tend to fail on their own unless some other fault causes them to overheat and burn out
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Re: Alarm clock very low sound « Reply #2 on: March 07, 2020, 10:40:28 PM » Author: Cole D.
I noticed the volume does seem to go up and down when I turn the wheel. Plus I set the alarm to go off and I could only hear it with ear to speaker as well.

Inside I didn't notice anything amiss but the parts are so close together it's hard to really see very well. There is the typical old electronic smell inside that makes me think maybe capacitor did go bad.
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Medved
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Re: Alarm clock very low sound « Reply #3 on: March 08, 2020, 04:24:57 AM » Author: Medved
Worn out.

No way. Barely 12 years should not wear anyrhing out, except the capacitors. And even that is very unlikely, as in those radios there is nearly no load on them.
This is no high power device, where even the special components are loaded near their limit like e.g. a light ballast.
Here in such radios even the cr@**iest cheapest parts have virtually tons of margin so last long.


There most likely something physically broke - often something related to controls (the paper substrate of the volume pot, connectors, switch,...). Or the backup battery have leaked and caused some corrosion damage.
Open it and have a look inside.
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Re: Alarm clock very low sound « Reply #4 on: March 08, 2020, 04:33:53 PM » Author: Medved
I disagree. Today's electronics are cheaply made and usually from China. Better to replace it than try and repair.

The cheaply made is not in components alone, but in combination of components vs their loading by the design. So for a function where the components are loaded/stressed, they use the standard ones, for which the load is on top of their rating. Namely filter capacitors in flyback converter based power supplies, lamp ballasts, chargers and so on. These then fail not because they are worse made than they were 40 years ago, but because they are loaded 100x more than they use to be in the small transistor radios of that era.

The thing is, these clock radios load those components in a manner similar to the load from those old transistor radios: So very little, so no way it could be normal wear.
What is very likely is either some abuse (the clock had fallen on the ground yielding some cracks, leaked battery,...) or was wrongly assembled from the start (tension in wires yielding to their breakage is very common)

But I didn't say it is not failing due to shoddy manufacture going too cheap. I just said it can not be a normal component wear.

But based on the symptom of low volume:

What could help me to guide is to know what ICs are there.
Very often it is some rather easy to repair thing (to make it working - sometimes it may involve making the push buttons protrude through the cover because the very popular metal membranes on a PCB usually need to be replaced by complete tactile switches,...).

Often when the raqdio uses a pot for volume control, it uses to be dirty. Be aware, many ICs use DC voltage to control the volume (many analog chips like CXA1691 and its relatives, all DSP based radio IC's using analog controls), so bad pot does not exhibit the typical crackling noises (the pot just generates a control voltage, which then sets the volume; either via an analog attenuator like in CXA1691 receiver or TDA1052A audio amp or many other similar, or controls the output DAC amplitude of the DSP based ones, like nowadays popular AKC1691, KT915 or so). In all these cases, the volume just gradually goes up/down (because the control voltage is so filtered either by a capacitor with the analog ICs, or by the DSP filtering in the DSP ones) when the contact is intermittent, or drops to nearly zero or some minimum when the contact is lost.

Other fault could be bad output cap with IC's using half bridge output (most analog fully integrated radio IC's) - there the cap may have just suffered from mounting abuse (leads pulled out of the case by force when the bulky cap is crammed to its place; this is not the cap fault, but shoddy assembly one).
Or similar: With a TDA2822 (or its clone; very popular audio power stage to work with radio chips not integrating power amplifiers, like TA2003, SI4825, KT915 or so) amp very often the electrolytic of about 22..100uF between pins 5 and 8 uses to be open circuit (again, most frequently again due to abuse during assembly as it is rather large value component; its load is barely few 10's of uA AC and few mV DC bias).

Mainly with the modern DSP based receivers with the speaker directly connected to the IC itself (AKC169x,...; even some modern audio amp ICs have similar feature too), a bad supply connection exhibits itself just as low volume (the voltage drop at that bad connections triggers the low supply volume reduction function, which is originally designed to prevent distortion by reducing the volume when batteries go weak; usually the algorithm is so perfected it makes no distortion nor similar artifacts tradditionally showing weak or bad supply; hence just the low volume).
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Re: Alarm clock very low sound « Reply #5 on: March 08, 2020, 07:04:22 PM » Author: Medved
Well, it depends.
Short term, maybe. Long term, in most cases not. Because there use to be usually one type of defects and once you fix it, it then uses to work forever.
But when you buy a new one, you have similar problem back a month after the warranty expires (that month is the work of Mr. Murphy).
Plus you learn something.

Plus for me it uses to be faster to fix such thing than searching for a replacement...
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takemorepills
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Re: Alarm clock very low sound « Reply #6 on: March 09, 2020, 01:34:38 AM » Author: takemorepills
Turn clock radio over.

If it says "Made in China" throw it into the round file and move on.
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High Intensity
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Re: Alarm clock very low sound « Reply #7 on: March 09, 2020, 02:01:19 AM » Author: High Intensity
I would think mechanical parts (switches, potentiometers, maybe even the speaker) would be the first to go in these things.

Turn clock radio over.

If it says "Made in China" throw it into the round file and move on.

I don't fully agree with that, i think if it can be fixed, then that would be better than tossing it and buying a new one, even if the item is made in some corner of China. Besides, if he did get a new unit it started having issues, I'll bet that it would be harder to fix compared to the older one as companies rely more and more on tiny SMD components and proprietary/blob microcontrollers.

---------------------

One thing that would be helpful to see is photos of the top & bottom sides of the PCB.
« Last Edit: March 09, 2020, 02:07:31 AM by High Intensity » Logged
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Re: Alarm clock very low sound « Reply #8 on: March 09, 2020, 12:05:05 PM » Author: Medved
I'll bet that it would be harder to fix compared to the older one as companies rely more and more on tiny SMD components and proprietary/blob microcontrollers.

The "blob" microcontrollers never failed on me, the problem was always elsewhere, so I would not worry that much for these. Just to be careful to not blow them up by some falling wire or so, but that may destroy anything to unfixable state within fraction of a second anyway.

You would have to equip yourself for SMDs:
So decent thermally controlled soldering iron with controller, suppply, stand and cleaner,
reasonably scaled set of tips (most frequently used by me: 2.4D is the universal workhorse, then 5D for large heat demand and ranmge of BCF1 and BCF2 for finer work; then the K is usable for longer rows, I do not use it that often but it uses to come with the kits)
flux pen or a syringe with flux (I have both),
SN63/Pb37 (better avoid the lead free as they are harder to work with) solder with at least 2% flux core
Solder wick
set of tweezers
Plus a syringe with some solder paste (a mixture of "powdered" solder alloy with flux, forming a paste) - quite comfortable to use ("glues" components in place before soldered), but uses to degrade over time, so always buy only small quantity. The syringe is essential, it is not that easy to transfer it from the cheaper pots into the syringe, so better to spend the ~20..30% extra on the syringe format

For the soldering iron my favorite is "Hakko T12" based stations very cheaply available at famous online markets (as kits with the handle and controller, usually the K tip is included).
The supply, controller and handle could be virtually any clone (there is nothing special; I recommend a separated controller and 19 or 24V power supply unit), but make sure you order the original Hakko T12 tips (those tips integrate the heater, temperature sensor and the tip itself into one unit, so it is very quick on warmup yet does not suffer from poor thermal contacts)
It really is really fine, yet at the same time really powerful for larger components (e.g. soldering onto 3mm thick steel body of an old radio capacitor is not problem with some of the larger tip, yet you can keep the thermostat still on reasonable 300degC).

It makes the work way easier even on non-SMD things, as you will more likely avoid PCB delamination problems common with the old paper/phenolic resin substrate boards or on some heavy gauge wires.
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takemorepills
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Re: Alarm clock very low sound « Reply #9 on: March 09, 2020, 12:14:14 PM » Author: takemorepills
If an electronic device is malfunctioning, and it uses a mostly SMD PCB, the easiest way by far to attempt to fix it is to reflow the PCB.
That's best done with a reflow oven.

Fixes lots of things usually, as SMD PCBs suffer quite frequently from solder joint failures too fine to see. This is particularly true of low-end electronics where low-cost SMD practices were used. Not common on a smartphone anymore as the manufacturing process for "better" devices is very well controlled these days.

Again, round file it. It's not worth it. I have Hakko rework equipment at my office. Thousands of dollars in desoldering, soldering, rework, etc.
You'd need to spend a few hundred to even get a cheap reflow oven, to fix an alarm clock?
Or sit down and just dink around with it? I guess if you have nothing better to do.
Even though I have everything to fix stuff like that (including DSO, bench power supplies, bench DMMs) the first thing I would do is put it in the trash.
Not even the recycle. Just the trash. Because China stopped accepting their junk back...err I mean "our recyclables" unfortunately many items that go off in your recycle bin (at least in USA) are now being buried in landfills. Only valuable metals are being recovered at this point.
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Re: Alarm clock very low sound « Reply #10 on: March 14, 2020, 03:03:05 AM » Author: HomeBrewLamps
Here is mine. It has been going for 38 years. Almost constantly.
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Re: Alarm clock very low sound « Reply #11 on: March 14, 2020, 01:34:40 PM » Author: takemorepills
Here is mine. It has been going for 38 years. Almost constantly.

See now, that's a keeper! The Chinese made stuff that dies in a few short years? Nah.

I have some GE clock radios from 1981, made in Malysia, blue VFD and lighted radio dial. Work like I remember them working when they were newer.
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Cole D.
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Re: Alarm clock very low sound « Reply #12 on: March 14, 2020, 01:38:08 PM » Author: Cole D.
Here is mine. It has been going for 38 years. Almost constantly.

Is there a date code on the bottom? If there is the second number is the last digit of the year.

Not to doubt you, but I really think that unit is more early to mid 1990s at the oldest. The 80s GE clock radios were more boxy and usually had the blue/cyan numbers.
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Re: Alarm clock very low sound « Reply #13 on: March 14, 2020, 02:34:35 PM » Author: HomeBrewLamps
Date code is 5531p.

My father said he got it in the 80's. (he was the original owner)

I guess the five make it either 1985 or 1995. I doubt this is 90's though just because my father has said he's had this longer. Even so if it is really from 1995 it is still 25 years old. Far outclassing most alarm clocks.
« Last Edit: March 14, 2020, 02:40:37 PM by HomeBrewLamps » Logged

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