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PostPosted: Mon May 13, 2019 10:39 pm 
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Location: Lake Forest, CA
Anyone know what it means when the voltage regulator outputs 5V when breadboarded, but NOT when installed into the power modulator? Needless to say, my nes won’t power on. I already did a full cap replacement on power modulator and nes mobo, same result.

I do have Tim Worthington’s NESRGB board installed and the console was working well for weeks. Then all of a sudden, the modulator has become finicky. Tested everything, pin 1 of the regulator receives 12V, pin 3 outputs nothing. I know it’s not the regulators as I’ve tried multiple, and have also pulled out and tested hooked up to a 9V battery separately, and they output fine 5V there!

There’s two NPN transistors in the power regulator labeled C1740, that I’ve pulled to test. Although I think those are related to the stock A/V outs. Those shouldn’t have to be installed for the regulator to output 5V should they? I think they’re bad: black probe on middle pin and red probe on pin 1, I get 0. Move red probe to pin 3, then I get 0.68V-ish.


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PostPosted: Mon May 13, 2019 11:04 pm 
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subotai wrote:
Anyone know what it means when the voltage regulator outputs 5V when breadboarded, but NOT when installed into the power modulator?
Something's shorting its output. Check what else is getting hot when you try to turn on the NES.

Quote:
There’s two NPN transistors in the power regulator labeled C1740, that I’ve pulled to test. Although I think those are related to the stock A/V outs.
Correct.


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PostPosted: Tue May 14, 2019 8:40 am 
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You are saying that from pin 2 to pin 1 you get 0V, and from pin 2 to pin 3 you get 0.68V?

Does the regulator get hot? Be careful checking, it might get REALLY hot. Or it could be room temperature, let us know.

With the regulator removed, what voltage do you get from pin 2 to pin 1 on the circuit board?


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PostPosted: Tue May 14, 2019 1:54 pm 
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Ben Boldt wrote:
You are saying that from pin 2 to pin 1 you get 0V, and from pin 2 to pin 3 you get 0.68V?


...when testing the NPN TRANSISTORS, NOT when testing the 7805, correct. You did a little bait and switch there, you got my quote about the transistors, yet put a pic up about the regulator.


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PostPosted: Tue May 14, 2019 10:03 pm 
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Did you really mean "bait and switch"? I had to look that up.

I was trying to help you and I misunderstood. I did think you were talking about the regulator.


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PostPosted: Wed May 15, 2019 1:10 am 
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I’m not necessarily saying your bait & switch was intentional :) . Anyways, I solved the issue.

If PS2 isn’t hooked up properly, then you’ll repro my problem. PS2 is one of the 5 bulky pins that interface to the NES mobo from the power modulator. I’m going to take a guess and say it stands for “Power Switch, pin 2”. There’s a also a PS1 pin, right next to it, and guess where these route to? Straight to the power switch’s pin 1 and 2.

So the way these pins became disconnected was that....well, I disconnected them since I desoldered the power module to get at the caps needed to be replaced. So I must have killed some plated vias is my guess. Once I ran conductor from ps1 and ps2 to legs of .01u caps on the mobo that we’re along the traces for pin1 and pin2, viola it worked again.


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