Firepower Diode Testing... Need Help

Zack5959

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I made a post a few weeks back about this problem.
The game just lights up and wont play, but will play just fine if you turn it off then on real quickly. I thought it was the 5101 but someone said it would not play games if the 5101 was bad. The I got a message to check the Diode near the Batteries.

See the pic and follow along....

I have it on Diode test mode on the multimeter.
Red lead on the right side
Black lead on the left.

Reading is -625 (yes negative)

If I switch the leads I get no reading at all.

This diode has been replaced with a larger one, but a negative reading? Is it bad?

Thanks!

FP.jpg
 
did you unsolder and pull it out of circuit to test it? That is really the only way you can be sure.
 
Ok took it out of the circuit and it reads 585 one way and nothing the other..... good right?
 
Are you sure that battery holder is letting juice (consistantly) get to the RAM chip? Remember, all is takes is a nano of a second of lost juice to the RAM.....and you'll get the issue you're seeing. Change that battery holder.....and then see what happens.

Edward
 
Are you sure that battery holder is letting juice (consistantly) get to the RAM chip? Remember, all is takes is a nano of a second of lost juice to the RAM.....and you'll get the issue you're seeing. Change that battery holder.....and then see what happens.

Edward

Yeah, I'm not liking that battery holder either. I see board rot underneath it. You probably need to give that board a vinegar bath to stop the corrosion, and then get a lithium battery conversion done on that board PRONTO.

I'd suspect anything below that battery holder may have issues. Look for discolored anything -- traces, pins, chips, etc. Do you see any green or grayish discoloration anywhere else from acid rot?

Can you send more closeup pics of the battery holder area and areas below it?
 
You could have checked the diode without desoldering it. Assuming that the voltage from the batteries is getting to the diode. Check for voltage at both sides of the diode then the 5101 RAM. If you have voltage on one side of the diode and not the other it's open. There should be a voltage drop of about .5V on one side of the diode (the banded side IIRC). If there's no voltage drop across the diode then it's shorted.

Ultimately you want to have the voltage from the batteries getting to the 5101 RAM with the game off. Check that voltage with fresh batteries installed. You can check at TP7 but I would also check right at the pin on the RAM (pin22). It should be around 4V. If it's much below that I would suspect a battery holder or blocking diode problem.

The battery holder is obviously a problem. I would replace it but you can use the tests above to determine if that's the only problem. I would go with an NVRAM rather than another battery holder personally. No more batteries required.
 
Wow, Ive done some pretty dumb things in my time, but this is up there.

I put the batteries in the wrong way LOL.

Ill get a new holder or Memory Capicitor and report back.
God im a dumbass.
 
Wow, Ive done some pretty dumb things in my time, but this is up there.

I put the batteries in the wrong way LOL.

Ill get a new holder or Memory Capicitor and report back.
God im a dumbass.

I would re-check the blocking diode. And deal with the battery holder, as you mentioned. In the mean time you might be able to work with what's there. With the batteries installed correctly ;)
 
I would re-check the blocking diode. And deal with the battery holder, as you mentioned. In the mean time you might be able to work with what's there. With the batteries installed correctly ;)

The board is on the bench.

WIth the batteries installed, I get 4.72v on the in side of the diode, 4.38 on the out.

Good?
 
So far so good. I would check at the RAM just to be sure but those numbers look good to me.

I have 4.38 on pin 22 of IC 19 (think thats what you wanted?)

No voltage detected anywhere on IC 13 or IC 16
 
Thanks everyone!
Ill plug it in tonight and see if it boots like it should.
 
Got everything back in and same shit. Have to open the coin door and flip the switch off then on fast and the.game plays perfect. 5101 bad???????
 
Well, if you just put the battery in, you're going to have to power cycle it at least once for the CPU to load the base audit data into the 5101.

Did you try it more than once?

-Hans
 
Well, if you just put the battery in, you're going to have to power cycle it at least once for the CPU to load the base audit data into the 5101.

Did you try it more than once?

-Hans

Wow. Works like a charm. Thanks! I love this site.
 
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