7805 Power Regulator question

Rob · Post by **Rob** » Tue Mar 08, 2005 1:14 pm

In chapter 3 pg 51 it has a diagram of the 7805 chip. My question is can the Input lead and the Output lead be reversed, or does it have to be exactly as labeled in the book?

JackFrost22 · Post by **JackFrost22** » Tue Mar 08, 2005 1:29 pm

Its a standered but always check the pinout on the box

Rob · Post by **Rob** » Tue Mar 08, 2005 1:38 pm

Ok, what did you just say? I am not following. Ben uses the 7805 thoughout the book, so let's keep it simple and use that regulator as an example.

HK-47 · Post by **HK-47** » Tue Mar 08, 2005 2:12 pm

Most 7805s are like that, but there is a few that are reversed. Thoughout the book, follow that example and you'll be good.

Rob · Post by **Rob** » Tue Mar 08, 2005 2:24 pm

OK, after doing some research, it looks like the 7805 has a specific input and output location, and thus cannot be reversed. From what I read, connecting it in reverse will almost immediatly destroy the chip - good to know. What I am leading up to with this topic anyway is that I am 98% complete with the portable Nes in Ben's book, but just can't seem to get enough voltage to the psone screen (+7.5 volts) from the wire on the right board (pg 159). If you look at pg 158, or 160, on the front right board- notice the position of the 7805 chip, as far as pin input/output. Now, on pg 159, it tells you to connect the Unregulated Power In wire to "X", but if I am not mistakin', that pin is actually the Output chip. I emailed Ben about this, but have not gotten a response. This could possible explain why I just can't get enough voltage to the psone screen. Can any other technical individual with ben's book look this over and see if I am right, or just going "batty" trying to solve my problem.

HK-47 · Post by **HK-47** » Tue Mar 08, 2005 2:38 pm

Your right... Thats wierd... That diagram is screwed... I think ben needs to look at this. Or maybe Im looking at the wrong datasheet. Though Ben should see this.

Rob · Post by **Rob** » Tue Mar 08, 2005 3:10 pm

Damn, I am glad it's not me going crazy. I have spent countless hours going over my wiring and re going over it, because I just can't get it to work.

jgibson · Post by **jgibson** » Tue Mar 08, 2005 3:38 pm

Which regulator is the correct one to use, a 7805 or the unregulated one? Also, Ben doesn't mention the catalog number of the 1 uf and the .1 uf capacitors. Does anyone know where I can get the correct ones. I saw a previous post that said that the 1 uf is 50 volts DC and the .1 uf has 104M written on it. I know nothing about capacitors and this has been a little confusing. I have a 1 uf capacitor rated at 250 volts DC and a .1 uf with 104 written on it but no M. Will these caps work?

Post by **Gamelver** » Tue Mar 08, 2005 3:46 pm

Rob: just solder a wire from the input of the 7805 to the input of the psone screen.....should work

Rob · Post by **Rob** » Tue Mar 08, 2005 4:20 pm

Gamelver, what about the rest of the wiring around the regulator (X,Y,Z)? It say's "Z" goes to the psone screen- do I also connect this to the screen, or just not connect use that connection. Or what about "X" the unregulated power in? Perhaps it would be easisest if you tell me where X,Y,Z come from and go to, because I think the diagram in the book is messed up. Thanks for the help.

jgibson, Yes, the detail is missing on a couple of these parts- I basically looked closely at the picture to see what Ben used. For the sake of simplicity, stick with using the 7805's. For the 1UF capacitor, you can actually take one off the inside of the RF unit on the NES- it's a 1uf 50v. You could still probably get away fine with the 250v one, except it may be a bigger cap, not sure. For the orange cap, as long as it's a .1 uf you should be fine. If you think this is fun, wait until you get to where I am at, unless ofcourse this issue get's resolved.

Post by **Gamelver** » Tue Mar 08, 2005 4:30 pm

all right, I'll actually take a look at the diagrams

......hopefully I can help you out

....

Post by **Gamelver** » Tue Mar 08, 2005 4:40 pm

hmmm...now that I look at it, I see that the screen gets its power from the 9v converted into 7.5v via resitors and capacitors.....I guess you should just go over ben's troubleshooting thing at the end, there's a part on the screen, and if all else fails, get some new components (like a new 7805, capcitors, etc.)...

Rob · Post by **Rob** » Tue Mar 08, 2005 5:14 pm

Well, my whole point is that if you follow his guide exactly, aren't we putting the voltage to the wrong pin on the regulator. Read my long winded post above for exact details.

Post by **Gamelver** » Tue Mar 08, 2005 7:46 pm

oh.....well, if you follow the diagram correctly, then you are inputting into the right pin, unless you have some kind of wierd 7805

....

HK-47 · Post by **HK-47** » Tue Mar 08, 2005 7:53 pm

Gamelver wrote:oh.....well, if you follow the diagram correctly, then you are inputting into the right pin, unless you have some kind of wierd 7805 ....

Well its a lm317t not a 7805, its an adj. reg...