Odd Cap on Asteroids Board

daley

Member

Donor 2011
Joined
Nov 15, 2011
Messages
396
Reaction score
0
Location
San Rafael, California
So, I am doing a Cap kit on my Asteroids board and I pulled a cap (C25) off the board that doesn't match specifications.

I first noticed due to the fact that there wasn't a matching cap in the kit I got from Bob Roberts. Double checked the picture on Bob's website:

http://therealbobroberts.net/asteroids.jpg

Then confirmed by checking the Asteroids manual.

The cap (C25) I pulled was a 4.7uf 50v, while specs (Asteroids manual) says that it should be a 1uf 50v (which is what Bob Roberts says it should be as well).

All the caps looked like they were original, and by that I mean they were covered in years of dust :)

So, two questions: 1. Any chance my board is different and I should replace it with a like 4.7 uf or go ahead and stick in the 1 uf? and 2. Assuming the 4.7 uf was installed by someone else at some point, could this have been causing/caused some yet unknown damage?
 
C25 is just in a circuit that holds the RESET line low for a brief period when it's powered on (or when you press the reset button).

It, along with R33, form an "RC" circuit. The time constant of it can be calculated by multiplying the capacatance by the resistance: TC = R*C = 10000ohms * 1 microFarad = 10ms. With a 4.7µF cap, the time constant will be more like 50ms.

I wouldn't think the difference is any big deal. It should work fine with either value. Changing the cap value will not cause and damage, only change the duration of the reset pulse. You can put in the 1µF or get a 4.7µF for it.

And for the record... In general, I'm not a big fan of "cap kits" for PCBs. The caps on PCBs have a much better existance than those in monitors and power supplies, as the don't get as hot, nor see as harsh of duty. I'm sure Bob only put together the kit to satisfy demand for people who developed a phobia of all "old" electrolytic caps... but I doubt very many electrolytics on Asteroids PCBs have gone bad.
 
Last edited:
Thanks, went ahead and put the 1uf in.

I wont lie I probably fall into the 'phobia' category. In this specific instance I am doing the shotgun approach to fixing the game. I pulled everything out to clean/restore the cab and while I have it all out I am essentially working on everything. Monitor cap kit, PCB cap kit, A/R repair kit, and power supply kit.
 
I wont lie I probably fall into the 'phobia' category. In this specific instance I am doing the shotgun approach to fixing the game. I pulled everything out to clean/restore the cab and while I have it all out I am essentially working on everything. Monitor cap kit, PCB cap kit, A/R repair kit, and power supply kit.

No biggie. It's the classic "preventative maintanence" or "if it isn't bad yet, it will be soon" vs. the "if it ain't broke don't fix it" or "more possibility for causing real problems when fixing non-existant ones" philosophical dichotomy. There is no Right Answer...

Personally, I started out in the former camp, but recently have been migrating to the latter.
 
Thanks, went ahead and put the 1uf in.

I wont lie I probably fall into the 'phobia' category. In this specific instance I am doing the shotgun approach to fixing the game. I pulled everything out to clean/restore the cab and while I have it all out I am essentially working on everything. Monitor cap kit, PCB cap kit, A/R repair kit, and power supply kit.

When I had my Asteroids I did this too. Bought everything Bob had to offer. Make sure you reflow the header pins on the monitor PCBs- this seems to be imperative preventative maintenance too.
 
Back
Top Bottom