Re: Atari STUNT CYCLE - service bulletins?

John Robertson wrote:
> Rodger Boots wrote:
>> My God, that is one total abortion of what should be a simple circuit!!!
>>
>> I don't see any good reason a 5K pot shouldn't work, they don't
>> mention what taper (linear, log, reverse log, etc.) the pot should be.
>>
>> What is the problem exactly, doesn't go slow enough, doesn't go fast
>> enough, what? I assume (very dangerous) that it doesn't go slow
>> enough. If that's the case maybe Q14 isn't grounding one end of the pot.

Actually it turned out to be a defective 4016 CMOS switch! I was not
paying attention to the fact that adjusting the added trim pot changed
the idle and run speed of the motorcycle. This trim pot is only supposed
to be effective on the higher wheelie and sets the maximum speed of the
bike. What was happening was the 4016 was behaving as if it had both
switches closed leaving the bike always running in high gear and hence
unable to accelerate correctly - leading to the inability to jump more
than 15 or so buses. Now it jumps just to the right edge of the screen
at maximum acceleration, throttle wound open keeping the bike in the
highest wheelie without flipping over.

Game now works well, customer will be pleased, I certainly am happy to
have figured it out - just wish I hadn't wasted so much time thinking it
was a bad transistor...turns out the 2N3565 can be substituted by other
similar NPN transistors with little effect on the acceleration range/speed.

John :-#)#
>
> Hi Roger,
>
> It IS a very nasty circuit...I've been trying to repair one here,
> can't get it quite fast enough for jumping 21 buses, nor slow enough
> to crash unless you use a little throttle to clear the starting 8 buses.
>
> The theory of how it works is on page 8 & 9 of the operators manual.
>
> R2 and R3 feedbacks are throttle voltage dependent and affect the lift
> of the motorcycle vs speed, when you lift the front wheel the first
> step it won't accelerate as fast as if the wheel is on the ground, and
> the second lift step does not do much either, yet putting the 100KR
> pot in place of R36 (as recommended by Atari) does affect the low
> speed and also the maximum speed. It would have been nice if there was
> a suggestion of tuning the circuit included with the page titled
> "Stunt Cycle - Return Throttle Modification (B-0023)"
>
> I've tried the recommended mods, but I do not have the original
> transistor - 2N3565 and have tried a PN3565, 2n2222, and a few other
> 2N NPNs - none of which worked much better than any other one. Reading
> the manual and it uses a current amp for the 556 frequency
> change...not one of my better subjects.
>
> So, now it works, just not as well as it should. I've tried a few
> tricks - changed a few resistances, but as I don't
> really understand the operation of this circuit I can't really do much.
>
> Must see if I can turn up more service bulletins!
>
> Darn.
>
> John :-#(#
>
>>
>> On Wed, Aug 4, 2010 at 7:28 PM, John Robertson <pinball@telus.net
>> <mailto:pinball@telus.net>> wrote:
>>
>> Well, not a lot of action on this mail list these days...sigh.
>>
>> Working on a Stunt Cycle and having trouble balancing the
>> throttle - the manual and the two sheets about various mods don't
>> help much.
>>
>> The schematic calls for a 5K pot for the throttle (works poorly
>> with that installed), the board works better with the 25K pot
>> on the CTS-1 that I use - so I put the 25K pot in (as was in
>> when the game came to the shop), but the range of throttle is not
>> satisfactory. I added the 100K trim pot in place of R68, and that
>> allows one to adjust the minimum throttle and affects the high
>> end, but there are no instructions about its adjustment...
>>
>> So, does anyone have any service bulletins for the game?
>>
>> Thanks,
>>
>> John :-#(#
>>
>> --
>> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
>> Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
>> www.flippers.com <http://www.flippers.com>
>> "Old pinballers never die, they just flip out"
>>
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>>
>
>
> --
> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
> Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
> www.flippers.com
> "Old pinballers never die, they just flip out"
>

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
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