Sony ICF-C12W Radio Clock schematics (power)

**R_J** · 11-30-2021, 11:46 AM

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

If you only want the radio to operate, changing the voltage would be ok but for the clock to operate, the input voltage is not the only problem, the frequency will be wrong and the clock usually uses the zero cross of the a/c sign wave to keep time.

Are you sure it does not have selectable voltage/frequency input? I see some specs on the internet that suggest it might. https://www.radiomuseum.org/r/sony_d...o_icf_c_2.html

**stj** · 11-30-2021, 01:51 PM

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

if it has a backup battery then it probably wont use the mains for timing,
but looking at this schematic, it probably has a special transformer to drive the vfd heaters

Attached Files

sony_icf-c10l_sm.pdf (7.77 MB, 34 views)

**eccerr0r** · 11-30-2021, 04:32 PM

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...

**stj** · 11-30-2021, 05:08 PM

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

well the transformer in the schem is 5-0-5 so maybe a 4.5-0-4.5 bell transformer would fit.

**UserXP** · 11-30-2021, 05:34 PM

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

Thank you all for this info.

Yes, I would like both the clock and the radio to operate. A full feature device.

No, I can't see anything inside that resembles a backup battery on the PCB. There is also no battery compartment.

No, this one does not have a voltage selector switch, although I saw a version with a round hole and a switch to set the input voltage. On the back of the case it says Input: 120V, 60Hz. But I guess all USA designated devices have this voltage rating.

The power cable goes directly into the transformer. It is rather a small one and completely encased in metal shielding of some kind (I will provide images if that would help). On the other side of the transformer there are those three wires coming out directly to the main PCB. There is also a small daughter PCB housing a LED display, a big chip and buttons for the settings and actions.

Do you think a socket power converter would be enough to start up the device? I came across this clock radio and took it because of nostalgia. It looks nice, isn't scratched and would make a great prop from the 80s. If we manage to bring it back to life, it would be icing on the cake.

**eccerr0r** · 11-30-2021, 05:52 PM

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.

**UserXP** · 11-30-2021, 06:14 PM

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.

**UserXP** · 11-30-2021, 06:47 PM

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.

Attached Files

icf-c12l.pdf (7.83 MB, 24 views)

**R_J** · 11-30-2021, 07:37 PM

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** · 12-01-2021, 02:57 AM

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.

**eccerr0r** · 12-01-2021, 10:43 AM

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.

**R_J** · 12-01-2021, 10:51 AM

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"

Attached Files

**UserXP** · 12-01-2021, 11:04 AM

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** · 12-01-2021, 11:10 AM

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** · 12-01-2021, 11:15 AM

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.

**UserXP** · 12-19-2021, 08:24 AM

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

Originally posted by eccerr0r

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** · 12-19-2021, 09:38 AM

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?

**eccerr0r** · 12-19-2021, 01:53 PM

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?

**R_J** · 12-19-2021, 05:29 PM

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

Sony ICF-C12W Radio Clock schematics (power)

Sony ICF-C12W Radio Clock schematics (power)

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