Fairchild Channel F System 2 Chip

[Nmitchn47]

Hey guys, just received my first Fairchild Channel F System 2 as a bday gift and was told it wasn't working. System turns on, led light is on and screen shows vertical lines in green, black & white. No sounds when anything is pressed. Unhooked the ribbon cable from the cartridge reader and no change as well. I swapped out the SL31291 chip with my Fairchild System 1 and it worked just fine, so it tells me the CPU is fine. No burnt spots or heavy oxidation on either side of the board. I looked into the VES manual and the technical guide is suggesting it's a possible PSU problem. Since this system is more compact, I can not make out what chip does what to isolate my problem. Anyone knowledgeable with this or the grandstand clone?

 

- SL31291 (CPU)

- SL31253 ??

- SL31254 ??

- FCM 9102 ??

- FCM 9101/N ??

- SCM90004C (x4) (RAM)

 

I'm going to check voltages tonight to be certain I don't have a feed problem. Thanks.

[Nmitchn47]

Power supply is good, capacitors and regulators are working. Definitely a chip issue at this point. Hopefully someone can chime in on what the chips are, primarily FCM 9102  & FCM 9101/N. Thanks!

[Nmitchn47]

7805 regulator was bad, open output leg at 153v. Checked it before and thought I read 5.2v, but after seeing high voltage at the F8 Chip, I went back. System purrs now. 

[student]

Resuming to add info some:

 

- SL31291 (CPU) = should be 3850 CPU

- SL31253 = should be one of the 2 3851 PSU

- SL31254 = should be the other one of the 2 3851 PSU

 

 

- FCM 9102 = seems to be used for controllers/audio/buffer

- FCM 9101/N = seems to be used for video; in some units it is labeled FCM 9111, maybe a newer revision.

 

Both FCM 9101 and 9102 seems to be chips integrating other components/circutiry that can be found on early fairchild hardware revisions (probably to save costs).