Is this Atari 7800 even worth trying to repair?

[+-^CrossBow^-]

You know...as 2 of the chips in the 7800 are the same as those used in 2600s, it is also wise to look for lots of busted 2600s on the bay etc. This is what I tend to do. Actually the small retro store just 5min from my house tends to get small piles of 2600s and they simple don't want to mess with them so I I've gotten a few of them for crazy cheap in the past to keep on hand for use as spare parts systems.

 

[livingonwheels]

That’s a good idea. I’m reluctant to purchase chips from eBay from China. I had ordered a few sets of chips from China for repairs on a couple Colecovision consoles, and it turned out that the chips were no good. Many hours wasted wondering why the chips weren’t working after I had installed them. I’m in the process of getting another 7800 through a trade on GameTZ. He said it worked last time he used it, so I’m hoping I can experiment a bit with the chips on that unit to find out exactly which chips are defective on this one. I will definitely order that tool you recommended though, for I don’t want to destroy a perfectly working console trying to fix the broken one.

[livingonwheels]

I replaced the RIOT chip today (6532) but it made no difference. I figure I may as well replace the 6502C as suggested. Which chip is that, for none of the chips on the board are labeled 6502C?

[+DrVenkman]

55 minutes ago, livingonwheels said:

Which chip is that, for none of the chips on the board are labeled 6502C?

Bottom left in your photo, labeled with the Atari part number CO14806C. 

[christo930]

On 12/17/2019 at 2:43 PM, ChildOfCv said:

Not quite.  Look at the very top of the first picture.

Do you have a kill-a-watt?  If so, you should plug it into the kill-o-watt and then plug a good 7800 into it and see if there is excessive draw.  You could always use a DC source and measure it if you don't have a kill-o-watt. Kill-0-watt meters are great for troubleshooting electronics.

 

If you haven't done so already, you should over the entire board with a magnifying glass.  While certainly not always or even most of the time, but at least some of the time, you will find physical problems with the board.  Given all the rust, there is reason to suspect physical damage.

[livingonwheels]

I just used a kill-a-watt meter. I'm was getting 8.8 watts on both the damaged, and a working 7800. But after 10 minutes I was getting 11.6 on the damaged console. I turned it off and on again and now it's hovering around 8.6 after 10 minutes. I still have to check the working console after 10 minutes to see what happens.

I see the CO14806C on eBay for $20. Seems too high (I paid $1.50 from AliExpress for the RIOT chip, so no big loss there). I'll see if I can find a damaged Atari 2600 and use the chip from that.

I was going to remove the chips from my working 7800 but decided against it, for I didn't want to potentially ruin a good working unit.

EDIT: I found the C014806C chip, used, on Ebay for $13. Is this the correct chip (they seem to all have different numbers on them):

https://www.ebay.com/itm/Atari-5200-Parts-1-x-ATARI-Sally-CPU-Chip-C014806-Tested-and-Working/123714376478?hash=item1ccdf3931e:g:FroAAOSwT4tZs3qH

Edited January 23, 2020 by livingonwheels

[+DrVenkman]

22 hours ago, livingonwheels said:

'll see if I can find a damaged Atari 2600 and use the chip from that.

That's not going to work, unfortunately. The 2600 uses a 6507, a reduced pin-count version of the 6502. Further, the SALLY used in the 7800 is an Atari-specific version of the 6502. SALLY is not particularly rare though - it was used by Atari for most 400/800 machines made after about 1982, it was used in all the XL and XE computers and the XEGS, and it was used in the 5200 and 7800. Best Electronics has SALLY chips for $8 brand new but there are caveats: Brad (the only) has very particular quirks about how he does business, his website is an antiquated mess, and there is a minimum order size.