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.

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!

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.

Purchased a Fairchild Channel F model 1 and the power supply brick was busted open. Wires were ripped out of the transformer and is beyond repair unfortunately. If anyone has an extra power supply laying around or one from a parts console, please message me. I would like to purchase a used power supply.

Spent a few hours on Christmas Eve comparing boards and I might be going crazy but both boards are doing the exact same thing. I relocated all the known good/new chips over to the newly acquired 7800 system, including the reset IC's Osgeld sent me, and so far no prevail. I'd much rather work on this new board due to it being a slightly older board with better traces and just cleaner looking. I'll keep the other board for parts. Moving forward, I've ordered DIP sockets to install on the board so I can swap out all the IC's. Need to check the Ram and OS chip first. Can the TIA and RIOT chips be interchanged from a known working 2600 to the 7800? Best Electronics is listing them too work.

Thanks guys for all the help so far. I think I will have to invest into a logic probe to see if the chips are functioning correctly for further diagnostics. But some good news after I'm almost giving up on this pile of plastic. Local gamestore is closing shop and I was grateful to have known the owner, so they let me look at their repair shop in the back and had a non-functioning 7800 for parts. I grabbed it alongside a few other 2600's to tinker with. It looks to be an earlier model with the expansion port but the board is the same layout. Now I can spend a day comparing both boards. I did snag a holy grail item that was sitting in a box over the side of the room. Early model Fairchild Channel F. Can't wait to look at this beast.

Update, the chips Osgeld sent me came in and the following was replaced with no change: - 4013 (U10) - 74LS174N (U11) - 74LS32N (U12) - 2N3906 (U8) Back to following the repair flowchart that I printed out for the system and it is saying to "check pin3 of 4013 goes low on depression of on/off switch". What does "low on depression" mean and how can I check that?

Yep, continuity is good on all three traces. Checked on both end origins while criss-crossing to see if they tapped into each other. Osgeld is sending me all three 3 chips for the reset circuit. Will update soon.

Crossbow, Dark Chambers, Pole Position 2, Ms Pac Man and Centipede

Surprised I didn't see this before but everything checked good with a continuity test on both ends of the traces for all three. Also no shorting between traces. Double checked continuity at the slot pins and motherboard while I was it. The cartridge guide had a sharp edge on the bottom plastic where it was pressing down on the motherboard and digging into the traces. Poor molding of the piece back in the day. Someone before me may have bashed the game in the slot figuring it would help fix it.

After looking back on the picture again, you might be on to something. I'll check them out later today.

Osgeld, I would be hugely interested in whatever leftovers you might have. PM me and I'll forward payment via Paypal.

Tested it after the regulator didn't work, working good.

I'm following the 7800 repair flowchart and it says to check a low depression on some of the pins. How would one go about doing so?

Before I cracked open the system, I had never seen one so large for a 9v setup.

I use gamevaluenow.com which keeps up with current pricing from ebay auction sites. So far it's been rather accurate and they offer an app.

Here are two vidoes that I uploaded this morning of the 7800 running a 2600 game and what is doing with a 7800 game. I got Venture to work this morning surprisingly. So it seems (3) 2600 games are working with a few presses of the power button. Take note of the different sounds and screens that are shown with the 7800 Dark Chamber game inserted. Each time I press the power button is something different. https://youtu.be/v0mZLunxCH0 https://youtu.be/Zb92OU8_hoM

Yes, one of the first things I tried. Used both a cartridge to clean and a credit card with a cleaning swab soaked in rubbing alcohol. Slot was not dirty at all. All pins look to be in place and not bent. This was before I knew the NTSC versions didn't have a boot screen. And yes, the first two videos didn't have the audio cable attached as I was more worried with the game loading. Audio from both jacks of the AV mod are good. Good to hear. That would be bad since I replaced all the larger electrolytic capacitors.

Zener came in the mail and installed, reading 5v and 5v at pin 14 on the 4103 now. No improvement still. Atari will still boot up Solaris/Pac Man randomly, but will not run any 7800 cartridges. I left Solaris running and picture will randomly glitch or get garbled and then return to normal every through seconds, sometimes it will run fine. I did notice the 6502 chip is running rather warm compared to the rest, don't know if that's normal. Side note, ran my voltmeter over the power supply end and it's measuring 11v. The regulator is measuring 11v input and 5v output to the board, this seems just way too high from the power supply. Is this ok?

Just ordered them, should be here by weeks end so I can update. Thanks for the link. If this doesn't work I'll order a socket and 4013 to test. I'm assuming that with roughly half the voltage required going to the flip flop 4013, it's barely functioning, but allowing the TIA to work?

Reading 2.1 volts at the zener and pin 14 of 4013. I'm assuming this is too low and needs to be 5v. What type of zenner can I replace it with?

2.1 volts constant it's measuring. Originally I was checking it by grounding and probing with the positive. Got Pac man to load and play but is finicky. Rechecked on my 2600 and it works like a charm. The graphics will jitter like a glitch. Solaris is working good but I'm unable to get other 2600 games to load. Still not a single 7800 game will load.

Well I take the back, after trying several games, Solaris magically worked for about 30 seconds. It took a second to load up and then it started to play. Once I was playing, it worked good and then the picture got scrambled and cut off. I got it back up and working again and wiggled the cartridge around and nothing happens, so no loose connection with the pins.

Just checked several working 2600 games on my 2600 and they will not work on the 7800. I checked the voltage at the CR5 and it's giving me 1.3v on one end, the other shorts the system out.