Sony ICF-C12W Radio Clock schematics (power)

[stj]

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

5-0-5 then.

[UserXP]

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

Update:
I found a 230VAC transformer that outputs dual 5.5V, it arrived today. It is also shielded, so it could have come from some audio equipment, which is a plus (it's used, but in good shape). Upon measuring its terminals without load applied, it actually outputs 5.7V on center tap and 11.4V total. So it seems to be within the measurements taken from the radio clock unit. Hopefully, it will help converting the unit to work with 220V mains.

[UserXP]

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

Here are the results. The replaced transformer provides ~0.2 lower voltage now that it is loaded than the original one did.

I used a replacement cable clip as the original one was broken.

I connected the input power to the PT with a joint. It is neatly fixed with an M3 screw which conveniently is placed in the hole next to the 220-240V marking - excellent as an input voltage indicator on the back.

I reattached all the wires. The little grey flat cable was especially challenging to solder without melting it, but it turned out great.

The tunner mechanism was too complicated for me to dismantle so I simply taped the string to its rollers so it doesn't unwind and then freed all the guides and rollers. It was worth it, plus it retained original indicator position.

It has been playing radio for the past two hours, works great. More testing and images coming soon.

[UserXP]

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

After a couple of hours of testing, I think this may turn out to be a good conversion. For reference, here are the previous readings with the original PT.

A for black (center tap)
C for one red wire
D for the other red wire.

The voltage between A and C is 5.7V.
The voltage between A and D is 5.9V.
The voltage between C and D is 11.7V

New readings with the replaced PT are:

A for black (center tap)
C for one yellow wire
D for the other yellow wire.

The voltage between A and C is 5.73V.
The voltage between A and D is 5.74V.
The voltage between C and D is 11.4V.

Do you think these voltages will be OK on the long run?

[stj]

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

yes,
remember, in 110v country's the voltage can vary by atleast +-10v so 100-120v
and in 220v country's the allowed variance is worse - 220-250v

the transformer output will vary with it's input so the clock has to be designed to operate over a reasonable range

[UserXP]

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

yes,
remember, in 110v country's the voltage can vary by atleast +-10v so 100-120v
and in 220v country's the allowed variance is worse - 220-250v

the transformer output will vary with it's input so the clock has to be designed to operate over a reasonable range

OK, that sounds great. I didn't observe any overheating or bad voltages. I checked the line that powers the OKI chip, the voltage is about the same or slightly lower than it was with the original power transformer which was run on a 220 to 110 volts power converter. The clock is operational, it shows quite an aqurate time, the radio sounds clear, no crackling, buzzing, humming or any other unwanted noise, the reception is great, so it seems it will work OK.
I also measured some of the filtering capacitors in there. The biggest filtering cap is Elna 16V1000uF, others seem to be Lelon or something like that, the letters are too tiny for me to see. But they all measure within their ratings, even after 40 years of age.
I wish I could see a modern device today lasting up to 40 years with no required service. In the past, things were built to last. Now they seem to have a planned obsolescence with a built in expiry date.

Thank you, guys, for helping me fix another piece of great equipment, this old-timer digital clock radio from Sony. Cheers!