pb908
Well-known
Hi, I just recently acquired a mint condition Yashica FC
looks very similar with my Yashica GL, specially the front lettering.
unlucky that when I put battery, metering always show HIGH lamp ON. so I decided to use my "breaking" talent to open all the assembly. Internally, just behind the front plate, there is a big PCB, and all components are lying there. As I begun to reverse engineering the schematic, I found out that the metering is controlled by one chip (I don't know if this is an OP-Amp, or Comparator, or transistor pair inside). but it is similar with the one I found on my Yashica GL.
It is 10pin DIP (Dual in package) chip, some of the pin are lifted out/up not use. the one it uses are:
- one pin for VCC (VBattery) and one pin for ground.
- one pin for the metering cell in series to either resistor or capacitor (selected when I push the shutter, that will be High/Low/Exposure resistor/capacitor)
- one pin connected to HIGH Lamp
- one pin connected to LOW Lamp and the exposure coil to hold the shutter leaf open.
the thing is I don't know what chip is this. so to replicate whatever it's function is hard. there are written but not that clear. What I can read is just NEC xxxxyyyy
looks like it's being made by NEC semiconductor in the past.
if any one open their Yashica and found/know what is the chip, I'd be happy knowing it's function and/or get the replacement.
Thanks a lot !
let me try to post some pictures later on
looks very similar with my Yashica GL, specially the front lettering.
unlucky that when I put battery, metering always show HIGH lamp ON. so I decided to use my "breaking" talent to open all the assembly. Internally, just behind the front plate, there is a big PCB, and all components are lying there. As I begun to reverse engineering the schematic, I found out that the metering is controlled by one chip (I don't know if this is an OP-Amp, or Comparator, or transistor pair inside). but it is similar with the one I found on my Yashica GL.
It is 10pin DIP (Dual in package) chip, some of the pin are lifted out/up not use. the one it uses are:
- one pin for VCC (VBattery) and one pin for ground.
- one pin for the metering cell in series to either resistor or capacitor (selected when I push the shutter, that will be High/Low/Exposure resistor/capacitor)
- one pin connected to HIGH Lamp
- one pin connected to LOW Lamp and the exposure coil to hold the shutter leaf open.
the thing is I don't know what chip is this. so to replicate whatever it's function is hard. there are written but not that clear. What I can read is just NEC xxxxyyyy
looks like it's being made by NEC semiconductor in the past.
if any one open their Yashica and found/know what is the chip, I'd be happy knowing it's function and/or get the replacement.
Thanks a lot !
let me try to post some pictures later on
sevo
Fokutorendaburando
Well, obviously it is a xxxxyyyy by NEC.
HTH Sevo
HTH Sevo
btgc
Veteran
Those FC'c are prone to metering issues, as I read around. Mine works, just underexposes by three stops. Suddenly this makes it hi-speed film shooter 
pb908
Well-known
Ha..ha..ha.. That xxxyyy is actually numbers but it is hard to read..
I was thinking if I can't get this chip replacement, I might try to junk all the pcb board and put a small microcontroller device to control both exposure&timer. May not working as it suppose to be, but at least it can work.
I just realize on Yashica FC, it have 2 coil, which one of them is use for self timer. When you press the small lever on the side of the lens, and turn it down, there is a switch inside that will enable the self timer which will be activated with shutter button. once you press shutter button, it will be hold down by the mechanical component untill exposure is done.. And the small lever will go back up as well.. Nice..
oh, and sorry for the double post.I got internet problem during that time so I don't realize that the first submition is already up.
I was thinking if I can't get this chip replacement, I might try to junk all the pcb board and put a small microcontroller device to control both exposure&timer. May not working as it suppose to be, but at least it can work.
I just realize on Yashica FC, it have 2 coil, which one of them is use for self timer. When you press the small lever on the side of the lens, and turn it down, there is a switch inside that will enable the self timer which will be activated with shutter button. once you press shutter button, it will be hold down by the mechanical component untill exposure is done.. And the small lever will go back up as well.. Nice..
oh, and sorry for the double post.I got internet problem during that time so I don't realize that the first submition is already up.