Quick A/R II question regarding Fuses 4 & 5.

Jeff F

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Could two shorted diodes in the rectifier section at CR5-8 cause both F4 and F5 to blow? I've seen one blow before... not both.

(don't have anything in front of me except the A/R II right now so I can't test it out with the new diodes yet)

TIA, :beerchug:
Jeff

[edit]Forgot to add F4 and F5 in a Tempest block...
 
Check the orientation of the large filter caps on the AR-II. I bet you have one or more in backwards!

Could two shorted diodes in the rectifier section at CR5-8 cause both F4 and F5 to blow? I've seen one blow before... not both.

(don't have anything in front of me except the A/R II right now so I can't test it out with the new diodes yet)

TIA, :beerchug:
Jeff

[edit]Forgot to add F4 and F5 in a Tempest block...
 
Just checked, no luck. Although, I wish it was in backwards because I'd feel better about not blowing another fuse then. :)

I'll add that this was in a Tempest I sold this weekend and it worked fine until it was moved to it's final resting place(of course). Then after one game at the new owner's place it blew those fuses. :(
 
With the AR-II out-of-circuit you should be able to measure the diode drops across the rectifier. I would start there.

You could also try replacing the fuses and firing it up without the AR-II present, just to isolate the problem to downstream.

[edit] I see you already replaced them. Just plug it in and watch for magic smoke! :)
 
Made progress tonight... but it's still not working. The fuses aren't blowing anymore and we have +22v and -22v back. But on the Tempest board the 7815 was blown. After changing that out, I still didn't get +15v but damn the 7815 got hot quick. Ended up being a shorted CR4, 1N100. Only parts store open after 6pm was Radio Shack and of course they didn't have it. Our "real" electronics store carries NTE and it looks like NTE109 is a cross.

Tomorrow is another day.

Thanks for the help bit_s! :beerchug:
 
Local parts place had the diode. Now all the voltages are good but the watch dog is barking. Going to check the ROMs tonight after work to see if it's something that simple. ;)

/jeff says as he crosses his fingers and knocks on wood...
 
Just wanted to close this one out...

ROM 112 failed checksum and the 6502 was defective. Burned a new 112 and replaced the 6502 and we have deflection. ;) Only bummer was it took me an hour to get my Needhams PB-10 computer running since I moved it to the shed a few weeks ago... boy I hate computers! :)
 
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