Bad Bridge

Fudd

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Pole Position just went out, pcb board lights are out, voltages at the test lugs are extremely high, 20v on the cpu side and 40v on the video side.....needless to say i shut it off rather quickly...and i double checked those voltages as well.

replaced the 2 2n3055's on the ar2 to be safe and nothing, i just rebuilt both ar2's in the past 6 months.

tried a new big blue and nothing

tested the bridge and my readings are around .100 to .200 on 2 of them and on the 3rd it starts at .200 and climbs and never stops. so it looks like a bad bridge, whats the part# and would radioshack carry something like that?

this might be the part# 35A 200V KBPC-3502
 
They should. Otherwise get some from mouser.com or digikey.com
 
No... Radio Shack doesn't.

They carry a 25A bridge: Catalog #: 276-1185, but not a 35A one.

To properly test the bridge, unplug it... Otherwise you're reading through the transformer and through the caps and the rest of the circuit.
 
Anybody have the correct part#??

manual says its a 3A-MDA3501 does that mean 35amp 100v?

i seen another thread that said it was 35amp 200v, also does it matter if the voltage is higher? say could i use a 35amp 600v?
 
You can even go a bit lower on PRV (peak reverse voltage)... the rule of thumb is 2x the voltage it'll be handling on a regular basis. You can go higher just fine.

Current... I'd stay with the existing current rating of 35A. You can go higher, provided it'll even fit where the part is supposed to be mounted.

BUT... Are you really sure it's bad? You need to check it out of the circuit to see if it's really shorted. The AC sides will read shorted because of the transformer... and the DC sides will read low then climb like crazy because of the big caps you are reading.

If a bridge is bad you will generally eat fuses like candy.
 
replaced the bridge today, put it on the meter and it checked out ok but replaced it just because of the sight of it. still getting 20v on the cpu and 40v on the video side....what next, big blue? r29, r30 on the ar2s?
 

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Q1, Q2, and Q3 on the A/R board... along with any resistor that look burnt.
 
ok, q1, q2, q3, bride, big blues have now been replaced and i'm still getting 20v on the cpu side and 40v on the video side..i checked all the resistors and they ohmed out correctly while soldered...i'm guessing i need to go thru and remove one leg of each to find the culprit....it really cant be anything else besides a resistor at this point can it?

but doesn't one ar2 run the video 5v and one ar2 run the cpu 5v?? if one ar2 had a bad resistor it wouldnt make both run high voltage would it?
 
ok, q1, q2, q3, bride, big blues have now been replaced and i'm still getting 20v on the cpu side and 40v on the video side..i checked all the resistors and they ohmed out correctly while soldered...i'm guessing i need to go thru and remove one leg of each to find the culprit....it really cant be anything else besides a resistor at this point can it?

but doesn't one ar2 run the video 5v and one ar2 run the cpu 5v?? if one ar2 had a bad resistor it wouldnt make both run high voltage would it?
Yeah both ARII boards supply the +5 to only one board...not sure if one having a problem could affect the other...my educated guess would be no.
 
I honestly don't see how this is possible. I've NEVER seen an AR-II fail this way. Are you sure you're measuring the voltage correctly? Try measuring the 10.3v unregulated line at the ARII. What do you get there?

Think about it - the ARII takes only one input from the transformer block - the 10.3v unregulated DC. How would it output 40 volts?

-Ian
 
I honestly don't see how this is possible. I've NEVER seen an AR-II fail this way. Are you sure you're measuring the voltage correctly? Try measuring the 10.3v unregulated line at the ARII. What do you get there?

Think about it - the ARII takes only one input from the transformer block - the 10.3v unregulated DC. How would it output 40 volts?

-Ian

Man, I was thinking the same think. I don't see how this is possible. Maybe (and this is a BIG maybe) if the transformer was shorting in some oddball way....but even then, I'd expect fuses to blow. Have you checked your meter? Are the batteries going bad? Did it take a high voltage zap?

Edward
 
I've been using my meter for other game projects and it works fine. Its even auto ranging so i dont see how i could screw it up. im beginning to think the problem is in the power brick since both cpu and video boards have high voltage.

going to check the 10.3v later tonight.
 
I've been using my meter for other game projects and it works fine. Its even auto ranging so i dont see how i could screw it up.

I don't know... but those readings really don't make sense. Use the meter to check a battery or something and see if that comes out right. I just can't imagine a situation where an ARII could output 40 volts without being on fire at the time.

-Ian
 
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