Asteroids A/R board and cap kit

dogbowl

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Just received a Bob Roberts cap kit (His Atari A/R II-01 kit) and I have a question on the caps he included.

My A/R board has 3 1000u 25v caps but in the kit Bob included only 1 1000u 25v cap and 2 3300u 35v caps.

From what I can find, those larger ones are the capacitors that Asteroids Deluxe uses.

Would it be safe to use those on my asteroids? Would that then cause the sound issues people have when swapping A/R boards between Asteroids and Asteroid Deluxe machines?
 
My understanding is you can always go up on caps.

Karen

You can go up on voltage, NOT microfarads! You'll need to get the right uf caps at the same voltage or more. Do not replace a 1000uf cap with a 3300uf, you could screw something up royally!
 
The two 3300 caps are for the speakers.. Your Absolutly fine installing them.. Won't do any damage.. Pm me if you have any other questions
 
I just found the instructions for the cap kit and Bob Roberts does specify that the 3300u cap as an "upgrade". I can only assume that they are safe to use.
Oddly enough, he doesn't include C6 or C16 - the two smaller caps on the board. Anyone know why that might be?

(FYI, just tested out the AR board with these higher caps and all seems good)
 
Not sure why he doesn't include those caps? When I rebuild ARs I replace every cap, the bottle cap tranny, and the trannies/reglators attached to heatsink..

Most of the time the large 2200 and 3300 caps for speakers don't really need to be changed, but I'll do it anyway..

Reflow the solder under each molex connector, as they become brittle over time.
 
I recapped my Asteroids Deluxe AR1 board with Bob's kit, all caps were replaced and it works great.
 
You can go up on voltage, NOT microfarads! You'll need to get the right uf caps at the same voltage or more. Do not replace a 1000uf cap with a 3300uf, you could screw something up royally!

Really? I have always heard that you can USUALLY go up in both volts and farads. Some circuits require specific values but you won't damage anything by using higher values, especially in voltage smoothing circuits on PS boards.

Using lower values could make the cap fail catastrophically (KaBOOM!).
 
See this post: http://forums.arcade-museum.com/showpost.php?p=1927819&postcount=13

I actually did the calculations for the change in frequency reponce (differeny filter cut-off frequencies for each cap) but I forget what the results were. IMHO, it's really not really a big deal in this application; I doubt anyone will be able to hear a difference between the 1000 or 3300uF caps.
 
See this post:
I actually did the calculations for the change in frequency reponce (different filter cut-off frequencies for each cap) but I forget what the results were.

The output cap, along with the load resistance (the speaker(s)) form a high-pass RC filter circuit. The "cut-off" (roll-off) frequency with the OEM 1000uF cap (assuming a 4 ohm load) is about 40Hz. With a 3300uF cap, it goes down to about 12Hz.

I don't know if any of the sound circuitry generates much sound at frequencies below 40Hz, nor if the speaker(s) could reproduce them... but going from a 1000uF to 3300uF output coupling cap should theoretically "lower the floor", and increase the bass output a bit.
 
Would that then cause the sound issues people have when swapping A/R boards between Asteroids and Asteroid Deluxe machines?

What sound issues, specifically, do people have when swapping A/R boards between Asteroids and Asteroids Deluxe machines??
 
Oh, good, it has been documented. That saves me the trouble.

I reached essentially the same conclusion: the AR board on AD divides the input signal by 11 right off the bat. This is presumably because AD generates a larger audio signal level than Asteroids. And that difference is due to the different values of R86 (same callout on both boards). That resistor provides the negative feedback to the opamp. It's a 1K on Ast and a 10K on AD.

For fun, I did a SPICE analysis of the input RC networks of both games, to see their relative frequency responses...
 
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