My Heavy Sixer acts strange...

[Lodmot]

I have a heavy sixer 2600 model. I originally bought it for 34 dollars in non-working condition for the sole purpose of seeing if I could actually get it working.

When I first got it, it had no RF cable, wouldn't turn on, and had a bad PIA chip. I've given it an RF cable, replaced the PIA and fixed the switchboard so that it turns on now. At this point, the system is nearly perfect in functionality except for one last issue.

 

What happens is, at first, the system seems to play fine without any errors. But then over time, the fire button will automatically get triggered by itself. The weird part is, it happens only occasionally at first, then it slowly increases in the rate it does it. By the time 30 minutes has gone by, the fire button will act as if it's being completely held down all the time, even when you're not doing anything. The effect also happens without controllers plugged in, so it's obviously the system itself. I should also note that while this glitch is occurring, the system will however still detect regular fire button presses from the controller as it should be.

 

Upon researching the way the 2600 works, it seems like the issue has to do with the RIOT chip. I've already replaced all 3 chips, and from what I gather, the problem is still there anyway. I'm hoping there's an easy solution to this problem that doesn't require using a soldering iron, because I really would hate to mess up this unit, because it's a heavy sixer and such.. If I have to though, I probably will.

 

Even if the problem is the RIOT chip, I've looked around online for a spare RIOT chip which I can purchase, and found absolutely nothing.

 

Anyone got any ideas? Thankies.

Edited April 3, 2012 by Lodmot

[Syntaxerror999]

If you need a spare RIOT best electronics has them in stock.

 

http://www.best-electronics-ca.com

 

However according to the schematic the joystick fire button (pin 6) connects to the TIA (pins 35 and 36 respectively.) However along the same circut pathway on the heavy sixer for each controls fire button is a 22 upf capacitor and a 6.2v IN4736 zener diode leading into ground. A 10k ohm resistor leading into + and just before the TIA chip a single IC hex buffer (4050b). (Info from the Atari field service manual...also avalable at best electronics)

 

If I had to guess is say its the capacitor or the hex buffer that's the problem. If its on the silkscreen the caps are C236 and C237 the diodes are CR202, and CR203, the resistors R226 and R225 and the hex buffer is A203.

 

As a side note on later board versions its a little different. A 470pf cap leading to ground a 220ohm resistor just before the TIA and branching off from the 220ohm resistor is a 10k ohm resistor just before +. There is no IC hex buffer.

Edited April 3, 2012 by Syntaxerror999

[Lodmot]

Interesting..

Isn't there a way you can check a capacitor by seeing whether it buldges or leaks?

In a well-lit room, I can probably backtrack pin 6 to the TIA by its trace on the board and see what components are on it, and where they are on the board.

Edited April 3, 2012 by Lodmot

[Syntaxerror999]

I believe the cap in question is a ceramic disc and I don't know if they plump like the drums do. As for testing them I think you need an o scope and its usage is beyond my skills. To help you find the parts, download this file...

 

http://www.google.com/url?sa=t&source=web&cd=1&ved=0CCMQFjAA&url=http%3A%2F%2Fwww.atariguide.com%2Fpdfs%2FAtari_2600_VCS_Domestic_Field_Service_Manual.pdf&ei=BT17T4-yJITOiALNnZF2&usg=AFQjCNE1xZ6bgTQyDSLjWTZ7BiF0rgDOFA

 

And go to section 2 page 4

[Lodmot]

Alrighty. Thanks for the help.

I'm glad to know this now, because a cap will be much easier to replace than a 16 pin chip xDD

I'm nervous about messing up my heavy sixer when I do it anyway.

[Syntaxerror999]

Let us know how it went.

[Lodmot]

I shall. :3

[Syntaxerror999]

Check out page 4-27 of the doc I gave you. Covers issues with joystick and paddle fire line issues.

[Lodmot]

Ah, boy... This is gonna be hard for me to decypher.

I'm not really all that good with electronics.

It's probably easier if I'm looking at this diagram while I have the unit apart in front of me.

[Syntaxerror999]

Something I should of asked... Is it just the left fire doing this or is it both? If its both then that rules out the caps,diode,and resistors... If its both then a common part is at fault... ie the hex buffer or the TIA. Following the flowchart with the power on and a voltage checker should help you... But one thing you COULD try is to bypass everything between pin 6 and the TIA with a mockup of the latter versions boards more simplistic circutry on a breadboard to at least get it working properly. The center pin of the voltage regulator (looks like a big transistor with a heat sink should make a good ground and the right pin (outputting 5 v ) should make a good +... But don't confuse it with the left pin which is an input of 9v!!!! Correct orientation is with the serial number facing you and the metal plate that attaches to the heat sink facing up.

 

Of course this would require cutting a trace or bending the needed TIA pins up... Both of which sounds like a route you'd be unwilling to take. So desolder pin 6 of the controler port from the board, then get a spare chip socket, place the TIA in it, bend the corasponding pin in the spare socket out, solder to that and insert the whole thing into the origional socket. This sandwhiching will not interfere with the TIA as I have tested it myself.

Edited April 4, 2012 by Syntaxerror999

[Lodmot]

Uhh..... well.... that would probably work.

Part of the problem is, I am not trained in electronics.

However, yes, both controllers do it, but it seems to happen at different times, they don't press the fire button at the same time.

I stupidly threw out a spare board from a light-sixer that I was practicing using the soldering iron on, so I'd have to buy it elsewhere.

I seem to remember switching the TIA and the problem was still there. (I actually kept the three removable chips from the board I threw out by the way)