trouble with a couple of cartridges

[Erzak]

I bought a collection of 20 used 7800 cartridges on eBay, all of them work, but for two of them, they only work if I apply some pressure to the cartridge, pulling it slightly towards me.  The two carts are Galaga and Donkey Kong Junior.  I already had a copy of Galaga, and it works fine.  I read in an older thread about some games having thinner PCBs, and that causing issues with some carts, but I'd think both my copies of Galaga would have the same PCB?  I haven't tried anything as far as cleaning or checking the cartridge slot, other than using canned air on it when I first got the 7800 a few months ago.  I cleaned the contacts on the cartridge PCBs with IPA and q-tips.  Anything else to try?  Also, regarding cleaning, what is recommended to clean up the outside of a cartridge, just a damp paper towel, etc?  Unfortunately someone put their initials on a few with a marker, so not expecting that to come off too easily, but the price was good (I think), ~$15/game including Dark Chambers & Ballblazer.

[351cougar]

there are also threads on cart connector mating issues and suggested fixes maybe it was in 2600 forums? I don't remember. The pull it out slightly and it works rang a bell

[Erzak]

Thanks, will do some more searching.  I wound up removing the cartridge slot from the board so I could examine the connector better, and it seems to be in good condition.  Wondering now if there is a cracked trace in the problematic cartridge, since I have to flex it pretty significantly to get it to work.  Just watched a YT video on opening a 7800 cart, so will try that soon.

[-Joe-]

Hi Erzak,

 

 I always clean my Atari 2600 / 7800 cartridges by using 91% Isopropyl Alcohol + Q-Tips. I start by cleaning the outside of the cart ( but always avoid the labels ). Then I focus on the contacts. Afterwords, I personally use a flat pink eraser to clean the contacts ( at least 1 side because the eraser will fit ). Then I clean the contacts again with Iso. to ensure there is no eraser residue. I do a final wipe with some DeOxit D5 & G5 Gold on the contacts ( to protect ) ! Now you should have a nice, clean, ready to use cartridge ( unless there is something wrong with a trace, etc. ) I've only had 1 cartridge not work ( out of 300+ ) and it was a well used River Raid 2600 cart.

 

 As for the PCB being " Thin " , I have read about this....but have only heard of Atari 2600+ users talk about this issue . I have a 2600+ and have never had any issues myself. Only loading Activision games need some slight care that I have experienced.

 

 I would also recommend purchasing a " 1UP Atari 2600 / 7800 Console Cleaner ". They are available on their website or eBay. Just ordered 1 myself 👍

[Erzak]

I opened up the Donkey Kong Jr. cart to see if perhaps there was a crack on the PCB or something that would explain why it only works if I put pressure on the front side of the cartridge.  I don't see anything obvious.  The PCB alone behaves the same way, if I plug it in firmly, I get the Atari splash screen and then nothing else.  If I apply pressure to what would be the label side (pulling it towards the front of the console, then the game boots up fine.  Took some photos of the PCB, a couple of the contacts are a bit discolored, I cleaned them off, didn't change anything.  I do notice four solder balls on the PCB, any clue what those are for?

[Jinks]

Clean your pins. Easy fix. No reason to take it apart in the first place. Look how dirty they are! Btw may as well clean all your carts if you are not familiar with the process. 

[Erzak]

2 minutes ago, Jinks said:

Clean your pins. Easy fix. No reason to take it apart in the first place. Look how dirty they are! Btw may as well clean all your carts if you are not familiar with the process. 

I have cleaned them.  IPA, contact cleaner, used a soft brush.  This is the only cart I have that behaves this way.  What else would you suggest cleaning them with?

[Jinks]

An eraser.  They should be shiney copper. The picture you had posted is very dirty. 

Edited April 6 by Jinks

[Erzak]

1 hour ago, Jinks said:

An eraser.  They should be shiney copper. The picture you had posted is very dirty. 

Pretty sure it was just the lighting in that photo, they are shiny.  Here's a better one.  I went over them with an eraser and then IPA, still behaves the same way.

[+Mitch]

It is hard to tell for sure from the pic, but the capacitor by the cart edge looks like it is bent down and possible shorting something. Try straightening it up.

 

Mitch

[Erzak]

Got it working!  Even though the solder joints looked good, I hit each pin on the IC with my soldering iron and reflowed them a bit, and it works perfectly now.  Must have a cold solder joint someplace, and when I flexed the PCB, it was making contact.  Had to turn my soldering iron up to ~620, doubt they were using leaf-free solder back in the 80's!

[Jinks]

Great! Glad you figured it out!