Color Cells CC784 Repair & Restoration Log

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

I see the ones you mean now, the resistor is at the top here and the diode is at the bottom. So remove the resistor when adding the CR2032 socket ?

Did this fix work? I noticed that R4 does not seem to be in parallel with D3... Which means that the path of R4 is the only continuation from the positive terminal of the battery. One would need to jumper in place of R4 to complete the circuit.... Doesn't seem right.

[stj]

Re: Color Cells CC784 Repair & Restoration Log

it's been a long time, just look at the battery circuit and change it so you have a diode from the battery to the ram and another diode from the 5v to the ram
i think it was that simple.

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

I understand it was quite awhile ago. 2015 I think was when the OP was made lol. I am not quite sure which IC is the RAM.
I attached some full shots of the board, as well as images cropped in on the battery circuit with a few annotations:






I hope this will help jog your memory.

The Volt reading before R4 across D3 is 5.1VDC, and after R4 steps it down is around 4.4VDC. This is the resulting potential at the battery terminals.

So what you are suggesting is the removal of R4, and replacing it with another diode?

[stj]

Re: Color Cells CC784 Repair & Restoration Log

you got the ram - it's the 6116
replace R4 with a low voltdrop diode

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

Awesome, assuming the cathode of the schottky facing towards D3 and anode towards the positive terminal on the new battery holder.

Assuming a common 1N4148 diode work well enough?

[stj]

Re: Color Cells CC784 Repair & Restoration Log

4148 will work, but a BAT43 will let you run the battery longer
the lower the voltdrop of the diode, the lower you can run the battery down before it cant power the ram

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

Excellent thank you for the help. I'll report back in my success!

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

Modifications finished, here is the end result:



The voltage across the battery leads live is 0.50V. And it seems to be keeping memory so far..

Although it has an issue where the set time does not progress. This issue was present before the battery modification, not sure how or if this can be repaired.

But the unit seems fine other than that. Thank you all for the help!

[stj]

Re: Color Cells CC784 Repair & Restoration Log

are you using a dc psu or an ac one?
it looks like it has a rectifier for ac so maybe the time is calculated from the ac waveform

[Sheeshbajeesh]

Re: Color Cells CC784 Repair & Restoration Log

are you using a dc psu or an ac one?
it looks like it has a rectifier for ac so maybe the time is calculated from the ac waveform

So yes, it uses a transformer to pull the mains down to 9.5VAC at 4.2A, then there is a rectifying bridge on the main board after.

[stj]

Re: Color Cells CC784 Repair & Restoration Log

so it's probably tapping a signal before the smoothing caps to count the ac pulses.
it has to - it has no clock chip or crystal.