Sony ICF-C12W Radio Clock schematics (power)

[stj]

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

ok
it's pins 41 and 42 on the chip need to be re-wired for 24 hour mode.
41 would need to be disconnected and 42 would need to be jumpered to a different display pin.

you cant use the buttons to switch between 12 and 24 hour mode

[UserXP]

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

Here it is, assembled and functional. After 40 years, it works and looks great!
Thanks, everybody, for helping me out.

When there is an 80' music hit on a local radio station played through this clock radio, it's like a time capsule.

[UserXP]

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

One more question. Is the transformet in this unit a center tap one, and would it be designated as 13V, 6,5-0-6,5?

[eccerr0r]

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

There's a tap for the filament heater, does not appear to be center tapped however - off center tap...

[UserXP]

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

There's a tap for the filament heater, does not appear to be center tapped however - off center tap...

So finding a suitable 220-240VAC transformer with that specific output will be next to impossible?

I found a 6-0-6 transformer which gives a total of 12V, so I hoped it would work. But it would be off-center, right? Would it work or would it over/undervolt some of the components and damage them?

[eccerr0r]

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

Chances are if it's 12V center tapped, the center tap would be 6V and way too high for the heater.

[UserXP]

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

I didn't know there is a heating element inside. A heater?
So, could a resistor be inserted between the center tap 6V output to drop the voltage to the required 5.2V?
I guess the output voltage of the PT would also drop a bit after load is applied.

I found several PTs at a local shop which are dual 6-0-6 volts, a total of 12V of various VA, power and current. They are all 220VAC 50Hz input.
I tried leaving the clock radio running for almost six hours to test the clock. It works flawlessly after the Pin12 mod, but the rated 100W power converter I used became hot, even though it had just 5W of load applied. I wouldn't leave it running 24/7.

Any thoughts on this power modification? Schematics suggest output should be 11V and 5.2V center tap. That would seem to be a 5.2-0-5.8 transformer, right?

[stj]

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

try looking for a "bell transformer", 4.5v - 0 - 4.5v
aka 9v centertapped.

[UserXP]

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

try looking for a "bell transformer", 4.5v - 0 - 4.5v
aka 9v centertapped.

Bell transformers are what I looked for and found. The original PT is also of that type. It's the proper rating that needs to be selected.

[stj]

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

how big is the original one?

[UserXP]

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

It is small. Maybe 2.5x2.5x4cm roughly. The longest dimension is the base with holes for being fixed to the casing with two screws. Based on its small size, it is probably a 5W, 2x0.125A or so. I'm just guessing.

[eccerr0r]

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

Since you have the step down working, what is the voltage of the winding and tap?

[UserXP]

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

I will check with my multimeter. I followed the traces, black wire is A, red wires are C (half voltage) and D (full voltage). I see that black goes through a resistor to the first pin of the display marked as F. Is that the filament (heater) contact you were referring to?

[UserXP]

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

Chances are if it's 12V center tapped, the center tap would be 6V and way too high for the heater.

Could the marking T6-13CH on the original mean something like Transformer, center tap 6V, total voltage 13V, CHina? Maybe it's a 6-0-7, but Sony marked the two output voltages on it. In that case, a 6-0-6 12V transformer would provide the correct voltage for the 6V center tap, but slightly lower overall voltage (12V instead of 13V)?

The schematics also show the pin setup for the 24 hour mode. Pins 41 and 42 indeed need to go to different pins of the display, plus Pin18 to 11V connected. It looks tempting, but I would need to tear or break the leads and rewire the pins. It's just an idea, but the power transformer mod would be the priority, I don't mind the AM/PM symbols that much.

What are your thoughts on this PT label?

[R_J]

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

The original transformer is likely closer to a 10v CT, 5-0-5, this will give you around 13VDC. The AC voltage listed for the transformer is not the same as the DC voltage after it is rectified and filtered.

[UserXP]

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

The original transformer is likely closer to a 10v CT, 5-0-5, this will give you around 13VDC. The AC voltage listed for the transformer is not the same as the DC voltage after it is rectified and filtered.

Thanks. If that's the case, then teplacing it wil be "go to eBay and search", which would bring Chinese sellers whose pictures of the products are usually generic/stock, plus the 50 day long shipping.
The lowest dual output PTs I can find in a local electronics shop is 6-0-6. :/

[eccerr0r]

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

Again you have a multimeter, measure the voltage, go from there. Don't want to hook up your filament and have it burn out, might well throw out the whole clock if this happens...

[UserXP]

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

I measured it.

On the diagram, these wires are labelled:
A for black
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.

This is with load applied as the device turns the display on immediatelly after powering on.

I suppose we need to achieve the 5.7 and 11.7 values (although, according to schematics, they should be slightly lower). But then again, it is powered through a step down converter, maybe it's not producing 110-120V precisely.

Do these measurements help? Attached is the size of the transformer.

[UserXP]

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

This is measured exactly at the point the three output wires are soldered onto the PCB. The rotary switch was set to OFF, only the display switched on.

[eccerr0r]

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

Well you got your answer now, go get something that matches when you feed it your desired input voltage and fits in the allotted space!