6-Switch Tele-Games "Game Select" Crash.

[zborgerd]

Hello all.

 

I just picked up a 6-Switch Tele-games that works well, with one exception. The "Game Select" switch causes the console to freeze, or crash, when pressed. I've also observed the game mode increment repeatedly on at least two situations when pressed, but it's hard to replicate. Generally, the CPU just bombs and the image becomes distorted or black. In some games, it appears to continue to run the program but in a glitched state - never actually changing the game mode.

 

There was another post about the subject where someone had the never-ending mode increment problem, and I think that it was suggested to clean the switches. I've tried that, but it doesn't seem to help.

 

Looking at the schematics, the switches are pretty simple. Just seems to pull the pin on the RIOT to the common when the switch is closed.

 

Anyone seen this behavior before? Maybe a bad RIOT or problem between the address or data lines on the 6507? Maybe RAM? I've checked the traces and everything appears to be in good order with no physical damage. Initial observations would tell me that something is writing bad data to the RAM or the RAM is just defective. But games seem to run fine as long as the game select switch is never pressed.

 

This Tele-games is unusual, in the respect that it appears to physically be a light-sixer shell, made in Sunnyvale, but everything on the PCB appears to make it a heavy-sixer; from the heatsink on the VREG, to the missing channel select switch, to the ribbon cable. I can see no obvious signs that it's ever been serviced or opened previously.

 

Thanks!

Edited October 27, 2013 by zborgerd

[Syntaxerror999]

I'd say your assumption that the RIOT is bad... But double Check to see if the line for the switch isn't shorting out an address or Data line.

[zborgerd]

I'd say your assumption that the RIOT is bad... But double Check to see if the line for the switch isn't shorting out an address or Data line.

 

Thanks for the response. I also emailed Best Electronics with the details above and they responded that the RIOT is probably the first thing to check as well. I'm probably going to order a few of the various chips for future projects anyway. Might be a fun project to restore this one.

[shadow460]

I've seen quite a few consoles with bad RIOT chips as well. Matter of fact, I just replaced one this evening. BTW, RIOT is where you RAM is anyway, save for whatever onboard RAM your cartridge has. Changing the RIOT will eliminate the console's faulty RAM.

[zborgerd]

This is going to be one of my holiday vacation projects next week along with replacing caps on a Turbo Express. I have all three IC's. I'm going to check out the board and then start by replacing the RIOT unless I find anything else that's obvious.

[zborgerd]

Sure enough, replacing the RIOT resolved my problems. I was surprised to see that there were actually DIP sockets in this thing. Maybe that was typical for the 6-swtich units (I've seen a few other photos online that show this)? I was expecting to install DIP sockets for easy future replacement.

 

I was also surprised to see that the ICs appear to have been sourced from different companies (maybe not, since MOS licensed out 6502/7 and similar chips to everyone under the sun). The bad one in question here was a Rockwell chip.

 

While I had it opened, I also replaced the .22 uF capacitors to stabilize the incoming voltage, and this alleviated the weaker video when pressing the game select switch. I'm going to perform a similar repair on my 4-switch vader.

 

Thanks to everyone for all of the good info here!