Pole Position blowing 25A Fuse

Phetishboy

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My Pole Position was dead a few weeks back, so I replaced my big blues, cleaned up my transformer block and tonight replaced my 25V fuse. Game fired right up, I raced almost a complete race and the game died during the 2nd to last lap. Turned off the machine. Checked it out, the 25A fuse was blown again. Put in a new one, turned it back on. Booted right up. I checked the 22, 10.3 and the 5VDC both were where they should be. Let my son race 2 races, then shut it off. Turned it back on, and he raced a half a race and the fuse blew again. Before I waste this entire 5 pack of fuses, what should I be checking/replacing? These are 25A 32V sloblows, but they look different than the one I replaced. I got them from Bob.
 
If I'm not mistaken that fuse should be a 20A 32V (@ F3) I think the only thing that would blow that fuse and not blow any of the others is a bad bridge rectifier or the related wiring. Since it works intermittently, You should check the connections at the bridge rectifier and see if they are burnt or corroded.
I believe they are under the metal housing.
 
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I was curious so I pulled up the schematic and it looks like only the
unregulated 10.3V would be affected. This is the supply power to both A/RII boards (also the coin mech lockout coils but they are fused with F2) . If you have an ammeter you could amp out the wires feeding each A/R board (pins 3 and 6) to see which one is pulling the most current. There could be a whole bunch of different issues causing the excessive draw if it turns out to be an A/RII or you could just rebuild them both. If that turns out to be the issue.
 
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I was curious so I pulled up the schematic and it looks like only the
unregulated 10.3V would be affected. This is the supply power to both A/RII boards (also the coin mech lockout coils but they are fused with F2) . If you have an ammeter you could amp out the wires feeding each A/R board (pins 3 and 6) to see which one is pulling the most current. There could be a whole bunch of different issues causing the excessive draw if it turns out to be an A/RII or you could just rebuild them both. If that turns out to be the issue.

ammeter, eh? Never heard of it. I do have 2 rebuild kits here. You think the AR II's are causing it?
 
ammeter, eh? Never heard of it. I do have 2 rebuild kits here. You think the AR II's are causing it?

Well, I would definitely check the connections to each board and then physically inspect each A/R for hot components (just after the fuse has blown). Also visually inspect them for burned, discolored components and cold solder joints.
I would suspect either A/R, their related wiring, the wiring from the fuse to the bridge rectifier and after it as well. I found that some power bricks did call for a 25 A slow blow, so I'm sure yours is one of those (although it calls for 20A in the schematic).
 
The fuse (20A, 25A whichever it is) is on the AC side of the rectifier. I think the issue has to do with the fact that the DC side is filtered with a large capacitor (2 actually), which means the AC-side voltage is only greater than the DC-side for a small portion of the AC cycle. So the current is very large for that short time when the diodes are forward-biased and then 0 for the rest of the cycle (when the diodes are reverse-biased). So even if the current on the DC side is never out of hand, on the AC side is going back and forth between huge and nothing.

But this would mean it's a design flaw, and that couldn't be, as there are so many PPs working flawlessly with this design...

I might try taking one of the Big Blues out of the circuit. This would allow the voltage on the DC side to drop more quickly, and thus cause the AC-side to charge it a higher percentage of time, lowering the average current required to supply the same amount of power. This will increase the ripple going into the ARIIs, but they should be able to deal.

Looks to me like Atari was a bit cheap on PP. Double ARIIs, double filter caps, but only 1 xformer and bridge rectifier circuit to drive it all. Should have had a full power block for EACH ARII, IMHO. Cheap batards.
 
If I'm not mistaken that fuse should be a 20A 32V (@ F3)

As far as I know Atari sent out a bulletin at some point to 'up' the fuse to a 25A.

As to removing a big blue out of the circuit, really? I can do that? What do I do with the pos and neg leads that will be hanging there? Connect them with a bolt or something?

Both fuse block and crimp connectors have been replaced, though admittedly the insulated housings that plug into the tabs for the fuse in question are now black. Elutz actually told me to lose them (ON THAT LINE AT LEAST) and solder directly to the tabs.
 
Yup, What Dave mentioned.....check that fuse holder. Pole Positions devour them. I always cut the quick connects off of F3 when I replace the fuse block. Solder the wires directly to the fuse block. Quick connects can not handle the amps this ncircuit draws. The other fuses are fine with quick connects.....no need to solder those. Also.....what Greg mentioned....check the bridge. Look for browning/burnt quick connects on its legs, and discolored wiring leading to it. I also solder the wires directly to the bridge. This suffers just like the fuse at F3. Next, make sure the edge connectors at the mother board are good and tight. And lastly, check diodes CR2 (on the video board) and CR2 (on the CPU board). Look for cold solder joints, excessive heat, discoloration, etc. These diodes run hot and burt out.

Regarding fuse F3......Atari released a service bulletin advising to increase it's value to 25 amps. This (in my opinion) wasn't really a "fix".......it's just a delay tactic. This circuit runs at it's maximum threshold. Shit's gonna burn up. As Darren mentioned......these things were designed like ass.

Edward
 
Both fuse block and crimp connectors have been replaced, though admittedly the insulated housings that plug into the tabs for the fuse in question are now black. Elutz actually told me to lose them (ON THAT LINE AT LEAST) and solder directly to the tabs.

Phet, what am I gonna do with you??;)

Get a new fuse holder, cut off that burnt quick connector(s), cut out any browning wire until you get "good copper", solder that shit directly to the fuse holder.....enjoy Pole Position. (also, check that other stuff in my previous post).

Edward
 
I am telling you, either solder the wires on to the fuse holder or replace the quick disconnects. This is a known problem, and it also exists on Paperboy games too. Same BS fix with the 25a fuse too on Paperboy.

What is it going to cost you to try this? a little time? some solder? you only have to do the 1 fuse holder.

"Trust Me" I used to work for the government.
 
Phet, what am I gonna do with you??;)

Get a new fuse holder, cut off that burnt quick connector(s), cut out any browning wire until you get "good copper", solder that shit directly to the fuse holder.....enjoy Pole Position. (also, check that other stuff in my previous post).

Edward

Some people's children(Phet, Frizz)... they just don't listen. You tell them again and again not to pee on the electric fence, but they just have to experience that tingling sensation for themselves.:D
 
I am telling you, either solder the wires on to the fuse holder or replace the quick disconnects. This is a known problem, and it also exists on Paperboy games too. Same BS fix with the 25a fuse too on Paperboy.

What is it going to cost you to try this? a little time? some solder? you only have to do the 1 fuse holder.

"Trust Me" I used to work for the government.

Dave, this happens to ALL classic Atari games at some point.....Centipede, Tempest, Black Widow.......to name a few I've fixed over the years.

What's it going to cost him???......well, if he keeps it up.....it will eventually kill his transformer. So, I guess it'll cost him a transformer assembly:D

Edward
 
I had this problem with my Dig Dug, it was my first "it was just a fuse" game.

Yup, put enough hours on an Atari game.....and it's gonna happen. When you have a spare moment.....and if you have an amp meter rated high enough......pull that fuse and throw an amp meter across it. You will now be wondering why this isn't happening more often!

NOTE: make sure you have a high rated amp meter.

Edward
 
Why do I feel like Halley Osmet in Second Hand Lions? OK, OK, I'll replace the fuse holder, Dad(s). As to the bridge rectifier, haven't noticed anything burnt near it, but I'll check again.
 
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