Sony ICF-C12W Radio Clock schematics (power)

[stj]

Re: Sony ICF-C12W Radio Clock schematics (power)

no, that can cause damage - it's a 5v chip
link pin12 to pin1

is pin18 connected to anything?

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Yes, pin 13 goes through a 100K resistor (R106) directly to one of the transformer's red output wires and is connected like in the schematices, which is labeled 11V (line D).

According to these schematics, pin 12 should be connected to 11V with a jumper wire. On my unit, pin12 is not connected to anything, but there is an unoccoupied hole on its pad for soldering a wire. There is also an unoccupied hole on the 11V line - just like the 50Hz schematics say there should be a connection between those two poins (my unit doesn't have anything soldered onto those two points). Does it mean that by joining those two points together the unit will auto switch to 50Hz?

What about Pin18, how to mod that one?

[stj]

Re: Sony ICF-C12W Radio Clock schematics (power)

check pin13 (50 / 60Hz sensing)
on a 50/60 switching clock that pin goes through a 100k resistor to the transformers highest voltage output (13v) before any diodes.

then make sure pins 12 and 18 are connected to 5v which you can find on pin1
pin12 enables the auto frequency switching
pin18 enables the 12/24hour option

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

The power transformer has a printed marking T6-13CH on its visible top.

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

OK, I finally managed to take some pictures.

The chip is the 42-pin OKI MSM5550RSK. So this piece indeed appears to be the same as the one in the 50HZ "LW" unit we have the schematics for.
The resistors 104 and 105 and capacitor 102 are in one of the pictures. The orange capacitor value is 101, the green one says 56.

On closer inspection, the display really does have all the fluorescent bits to form digits 2 8 : 8 8, which probably scrolls between 12AM > 12PM > 24 hour mode while pressing the hour button when this function is not disabled.

Since it's the same chip, does this mean that this chip is perfectly capable of working with either 60Hz or 50Hz power line but is somehow hard-soldered to work only with 50Hz?
Also, the formable layout for digit 2 on the display indicates that 12/24 hour time mode is also possible to be set. It seems that these functions presented in the chematics exist with this model, it would be great to "mod" them.

What I couldn't find is the pin layout and function for this chip. I also can't tell which pin is number 1 as there is no groove on the chip housing.

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Thanks, guys. Well, the schematics I found are for the ICF-C12L model. My model doesn't have a 24 hour feature, the display only has lights to form digit one, there are no light pieces to form number two. So it is a fixed 12 hour format with AM/PM indicator.
I will try to locate the resistors and capacitors. Everything is so compact on the PCB, some components are really tight next to each other.

[R_J]

Re: Sony ICF-C12W Radio Clock schematics (power)

Your model should be setup for 60Hz and the schematic is for 50Hz, can you see what is different? maybe the circuit around pins 15~17 As you can see from the schematic, pin18 switches between 12/24h, maybe there is a separate pin that switches between 50/60Hz

[eccerr0r]

Re: Sony ICF-C12W Radio Clock schematics (power)

Yeah that's unfortunate. Autodetect is possible but kind of difficult, would need to make a internal oscillator to compare to, but if it's stable enough, why not use it to run the clock...

... then again there must be a reason for that RC network... What are the resistor/capacitor values for R104 R105 C102 provided they are the same designators on the unit you have?

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

I suppose there isn't a simple part to replace inside to make the clock work normally at 50Hz mains. Unless there is something else broken causing it to lag. What do you think?

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Despite having a PP3 to backup the clock, I'd be surprised if it doesn't require line power for clock operation.

But it might actually autodetect 50/60Hz...

Hello, people. Sorry for this late reply.
Unfortunately for me, you and R_J seem to be right.
I found a 220V to 110V adapter with stated 100W power as per your suggestion, the converter did the trick to power on this digital clock radio. But, because the AC line here is 50Hz, the clock seems to go slow. I synchronized it with my phone, and the clock slowly starts to be late minute by minute compared to the correct time. I hoped that since this is s digital device, it would use the crystal to count time.
I guess finding a replacement transformer with the 220VAC input wouldn't help much, except removing the need for the mains voltage step down device.

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Thanks, R_J!
I found something similar to the ones you included, 45W max power. I don't think this clock radio needs more than 10W, if that much. I certainly need to find a means to power the unit up to see if it even works.

[R_J]

Re: Sony ICF-C12W Radio Clock schematics (power)

I posted a picture of one of the convertors, there are others, less wattage and cheaper

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Thank you, I will investigate that. The service manual shows how to remove the band string and tune drum, which looks a bit complicated for me. I wouldn't want to mess the band indicator position. Unfortunately, in order to get full access to the main PCB, the radio station string mechanism must be removed.

[R_J]

Re: Sony ICF-C12W Radio Clock schematics (power)

Check where the wires on this transformer go. usually when you have one black wire and two red wires, the black is the center tap. I suspect in this case one of the red wires goes to ground and the black goes to the 5.2vac. Look at page 7 of your service manual
The secondary of the replacement transformer will likely be listed as 11vac center taped.
I would get one of the voltage converters that plug in the wall outlet and the radio plugs into it, even the small ones seem to be rated 50watts (radio is 5w)
Here is one I found so you get the idea of what I am talking about "Simran SM-250R Step Down Voltage Converter 50W"

[eccerr0r]

Re: Sony ICF-C12W Radio Clock schematics (power)

No, transformer buzzing is just audible noise, not electrical noise -- unless it's actually arcing which would add to thermal noise...

Just make sure it's a step down transformer, whether it's an autotransformer or not. At the wattage you're talking about I would hope nobody would use a phase control step down, now these you avoid for electrical noise.

It should be possible to get (nearly) silent step down transformers, all depends on whether you've seen any (nearly) silent line frequency transformer before.

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

So, I should look for a transformer of a similar size, rated something like:

Input (AC): 220-240V
Output (AC): 5.2V, 11V

The current PT has three output wires. I suppose the black wire is the negative or ground, and the two red wires are 5.2V and 11V, so I should find a transformer as close to this, right?

I found these schematics for the UK model, so that one is made to work with 240VAC mains, which hopefully means that they employed a universal output power usage and then just used a dedicated PT depending on the market the unit is to be sold on.

I think that replacing the PT would be a cheaper and a more convenient solution. Those step down power converters seem to buzz a bit and I don't know if that would be picked up by the radio as some kind of EMI. Which is probably why the original PT has shielding.

[R_J]

Re: Sony ICF-C12W Radio Clock schematics (power)

If you can find a replacement it should work, It looks like the micro can detect 50/60hz so I suspect the clock won't be an issue.
I would think a 220v primary and 11v secondary with a center tap would work

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

I managed to find the manual for ICF-C12L. The device looks identical to the one I have, maybe it will help you decipher whether a transformer replacement would work. It looks like it outputs ground, 5.2V and 11V.

I don't know what are the exact differences between the W and L model, except for the markings on the radio band selector switch. The "W" model (mine) has AM-FM, but the L model has LW-FM.

[UserXP]

Re: Sony ICF-C12W Radio Clock schematics (power)

Thanks, the step down is an option, although I will need to buy one. I didn't want do it initially because I was afraid it might make the radio clock malfunction or break down.

No, there is no openable battery compartment anywhere on the housing. Even if it used a 2032 3V button cell or alike inside, it is not the case. There simply aren't any battery contacts. It looks like it is powered through the transformer alone. There is one large capacitor near where the output wires are connected.

[eccerr0r]

Re: Sony ICF-C12W Radio Clock schematics (power)

The battery is a 6F22/PP3 and is likely offboard on the bottom of the unit if past experience with Sony "dream machines" goes.

It might just work with a step down 220V to 120V, else you'll need to replace the transformer as stj suggests. The worst case scenario is that the autodetect of 50/60Hz doesn't work and your clock will run slow. Looks like you will need around 10V RMS with CT on the secondary, so you can get 13+V P-P as the radio section appears to want 12VDC after the ripple filter.