Missing Components on a Clock Radio

[Bender]

Hi All

Apart from doing some basic electrical work back in high school (13 years ago) it would be safe to say that I have lost some skills and require some assistance.

I purchased a clock radio from the US (I live in Australia).

I then purchased a step down converter so it would work and it does just fine however the time is out by 10 seconds. Every “real world” 60 seconds the clock radio thinks it’s 70 seconds.

The manual of the radio states that it should be running at 120 V 60Hz. When I tested the Hz going through the clock radio with a multimeter is only comes up with 50Hz (Point C on the below image).

On the back of the clock radio there is a place where it looks like a switch should be to allow me to change between 50 and 60 Hz. It’s a big leap of faith although I’m guessing by making it run at 60Hz will fix my issue.

Upon opening the baby up and taking a quick look around it would appear that there is something missing on the PCB board that should link point A and Point B to convert the 50Hz to 60Hz. Point B registers at 50Hz although the other two points go nowhere (It’s not a double sided PCB).

The switch on the side adjusts the clock radios brightness and also set the time.

Would anyone have any idea what is missing?
Or tell me what I need to buy to make it run at 60Hz?

Any help would be appreciated, this clock radio is 25 years old and it’s a rare find as it was still new in the box. It would be great if I could put it to some use.

Cheers!

**broken link removed**


**broken link removed**

 

[pfofit]

It would be nice to see the other side of that little board. although it looks like it has a four wire ribbon cable a switch and a two legged device like a resistor or diode or such.

However, what is missing is most likely a slide switch that would have pin "b" as a common point. ( B is connected to many other points.) a and b would be connected for a 60 Hz environment and b to c in a 50 hz environment. If your notations are correct.

Sadly, you may be out of luck.
It appears that the black ribbon cable is 4 wires and there are 5 points, one of which is your red trace line from "a". The red line is obscuring the solder points.
Pad "c" seems to go nowhere.

So in 50 Hz land common "B" gets connected to "c" which is what you have now without the missing part. So it should work down under without the missing part. That's why I'm wondering if your notations are correct.

In 60 Hz land "b" gets connected to "a" which would go out on the ribbon cable to somewhere an adapt the counters to accommodate the change in frequency which they use to set the time base.

I suspect that there may be more missing than one might think if the distributors knew that the clock would only be sold in a area of 60 Hz. Or that little board and case were used 'cause they had a bazillion of them and the availability of different Hz is not possible, only 60 Hz.
For instance all of north america is 60 but south america has both 50 and 60 Hz dependent on country and most of the rest of the world is 50hz. Of coarse, there is japan which is 50hz in the west and 60hz in the east. go figure

Of coarse I'm only guessing/surmising on what you have, but it may give you something to think about.

Snap a clear pic of the other side to confirm what is/isn't there.

cheers

 

[pfofit]

Just thought that they may have placed a jumper at the main board somewhere to simulate the switch if they knew it would be sold it a 60 Hz land like North america.
cheers

 

[arhi]

I cannot remember the IC id most of those old clock radio's used .. IIRC, there was 2 version's of the chip .. one where you could choose between
- bring external 50/60Hz pulse (not selectable, depends on the chip version)
- if no pulse given, it uses internal oscillator (internal osc had error of cca 5min per day)
and the other one where you could choose between:
- bring external 50/60Hz pulse (not selectable, depends on the chip version)
- connect external xtall

This board looks (from this side) like
- use 60Hz from main power if 60Hz is selected
- use external oscillator (ne555 based or similar) to generate 60Hz if 50Hz switch is used
but, more can be said after you send the pic of the component side

There should also be one more board (LCD/7SEG board is usually connected directly on it) with the chip that is getting the job (fully integrated clock + lcd driver) .. snap a photo of that board, and we can probably help you find the data sheet for the IC driving the whole clock / help you modify it for 50Hz usage)

 

[Hero999]

Bender,
You've got that the wrong way round.

US is 60Hz and AUS is 50Hz.

Have you checked the continuity between pins A and B?

The chances are, there's a jumber or something on the other side of the board, you need to disconnect from A it and reconnect it to C.

 

[Bender]

Thanks for all the information you have provided with regards to my issue. Here is the back of the PCB, sorry for the low res image, I took it from my mobile phone.

**broken link removed**
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[Hero999]

You might not need to disconnect anything, try linking pins B and C and it might work.

 

[picbits]

As above ^^^^^

If it starts smoking then you know it was the wrong advice but either way you won't be able to use the radio until you try.

 

[Hero999]

I wouldn't worry about it smoking.

What clock IC does it use?

I've done a quick Google on alarm clock ICs and found a datasheet for the LM8560 and the LM8363D and both have a pin which enables 50Hz operation if it's pulled high or low depending on the IC. As these seem to be the most common ICs it woudn't surprise me if the clock uses eithe one or the other.

*50/60 Selective Input:
When 50/60 selective input is connected to VSS, 50Hz use is enabled. When 50/60 selective input is
left open, VDD is activated using an internal pull-down resistor and the setting is switched to enable use
at 60Hz.

https://www.electro-tech-online.com/custompdfs/2008/05/datablad.pdf

50Hz or 60Hz is selested by use of the 50/60Hz SELECT.
50Hz: 50/60Hz SELECT is set at 'H' level (Vss).
60Hz: 50/60Hz SELECT is set at 'L' level [Vdd} or left open.

http://www.datasheetcatalog.org/datasheet/sanyo/LM8363D.pdf

The chances are that this jumper just connects to the 50/60Hz select pin on the IC and is just left open on the 60Hz model and connected on the 50Hz model. Therefore all you'll be doing is connecting it thereby converting the clock to a 50Hz.

 

[Bender]

I found 2 chips one on the radio and the other just behind the display of the clock. CHIP ID

TMS3455NL-R

M (Symbol of a triage) 31400

The chip has 26 pins and i did a Google on it but all the data sheet links were bad. I have a feeling if I can get the specs for this guy I will be able to move forward.

 

[Mikebits]

I think the TMS part looks similar as the chip that Hero identified. I found a datasheet for a TMS3450. May just be crazy enough to try, I did not check the pincount though. Oops.
TMS3450NL pdf, TMS3450NL description, TMS3450NL datasheets, TMS3450NL view ::: ALLDATASHEET :::

 

[Mikebits]

I went ahead and checked the pinout. The 3450 has 28 pins. Is it possible you miscounted the pins? Anyways, in case you have trouble getting to the data sheet. Here is the pinouts.

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[Bender]

Yep I did miss count, I hadn't had my morning coffee yet....

I'm assuming now all I need now is short the power to pin 25 or 26 and test it out.

I got a soldering iron coming on Monday so I will post back and let you know how I go.

Cheers guys,
Mike

 

[Mikebits]

I think you should leave pin 25 alone.

 

[Mikebits]

Also, for 50Hz, I think you want to tie pin 26 to ground (Vss), not power pin. The data sheet seems to have an error when it says 60Hz pin left open is pulled down to Vdd. I think it should say pulled up to Vdd.

 

[Bender]

Thanks for the heads up!

 

[Hero999]

I would suggest that you don't mess around with shorting any of the IC pins, just connect pins B and C on the PCB, which are connected to the relevant pins.