Difficulty Switches??

[yelrah39]

hi  ive got an Atari 2600 question? i picked up a 6-switch. everything works as it should. my problem is, it only plays in the difficult mode?? even with both switches in the easy mode it still plays in the hard mode? ive repaired around 100 of these and never came across this before.. the chips are good and the 2 difficulty switches both tested good. the unit works perfect except for this. its both players not just one. im thinking its the Hex Buffer Cd4050? ive had to replace this before because the tank in combat kept firing. just looking for a little advise. thanks yelrah39

[alex_79]

2 hours ago, yelrah39 said:

im thinking its the Hex Buffer Cd4050?

No, the difficulty switches are not connected to the CD4050 (check the schematics in the 2600 service manual). They are connected directly to 2 pins of the RIOT (6532) chip. They connect those pins to GND when in "B" position, and leave them disconnected in "A" position.

Oxidation/dirt inside the switches themselves might result in them not making contact when closed, and so the games would see them always in  "A" position.

So, if you're sure that they are mechanically good, and there aren't cold solder joints or broken traces on the board, then the culprit is likely the RIOT chip.

 

BTW, you posted in the wrong sub-forum. This is for discussing about programming games for the 2600. You should have posted this question in either the main Atari 2600 or the Hardware sub-forums instead.😉

 

[yelrah39]

hi both switches are good and i tried another RIOT chip from a working machine and it still only shows it in difficult position?? dont really see any cold solders? ill recheck. thanks

[Mr SQL]

On 2/11/2023 at 5:06 PM, yelrah39 said:

hi both switches are good and i tried another RIOT chip from a working machine and it still only shows it in difficult position?? dont really see any cold solders? ill recheck. thanks

 

The switches may be oxidized.

 

RUN this program and try working the switches back and forth while pushing down slightly and then pulling up slightly.

 

You may see one or both difficulty switch status change intermittently if the switch is having trouble staying set, the process can remove oxidation preventing the switch from activating. 

 

This program will also test the BW/Color switch, I encountered a similar problem with that switch.

 

throwswitches.bin

[yelrah39]

Thanks, I found the problem. It was a cold solder on the ground of the left switch. Thanks again