J.Ivy Posted June 2, 2014 Share Posted June 2, 2014 So this is a simple thing, yet I still need help. The LED for my 7800 has burned out. Id like to replace it with a modern blue one (im tired of red), its a new millenia, its getting updated So im at a loss to find out just what voltage of LED I need for this. If anyone knowns what the on/off buttons LED voltage is, please let me know. Thanks for all your help. Quote Link to comment Share on other sites More sharing options...
jaybird3rd Posted June 2, 2014 Share Posted June 2, 2014 Red LEDs typically have a recommended forward voltage of 2.0 to 2.4 volts. These LEDs cannot be safely connected to a 5V supply without a current-limiting resistor, so the 7800 already has one for the old LED. It's been a while since I've looked at mine, so don't take my word for it, but it's probably a 150-ohm resistor (or some value very close to that). LEDs of other colors should also work with it, even though green and blue LEDs have a somewhat higher recommended forward voltage (3.0 to 3.4 volts). I put a green LED in one of my 7800s without changing the resistor, and it worked fine. To be on the safe side, you should check the specifications of the LED you intend to use (the manufacturer's recommended forward voltage and current), and then use a calculator like this one to determine the best value for the resistor; the larger the value, the lower the forward voltage across the LED will be. Using a resistor with a larger value than the one indicated by the calculator should be safe; the LED just won't shine as brightly as it otherwise would. Quote Link to comment Share on other sites More sharing options...
J.Ivy Posted June 2, 2014 Author Share Posted June 2, 2014 Thank you so much for the help. I will get on this in the morning, ive been getting my old 7800 back to funtional shape and well.. without the on/off LED, its not nearly as cool looking. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted June 3, 2014 Share Posted June 3, 2014 Didn't know anything about this with the resistor until now. You sure on this? I got a blue 5v one installed in mine and it has been working for well over 10 years now? Also put a UV one on my LHE modded one that is also a 5v and it seems to work just fine as well. But now that you mention this, I always wondered if the 5v blue LED on my 5200 wasn't part of the reason that 5200 started to behave so oddly out of the blue about 3 years ago? I figure if the current is only 3v then the LED would be dimmer then it should be but the blue ones I've used are near blinding when the consoles are powered on! 1 Quote Link to comment Share on other sites More sharing options...
uglyclone Posted June 3, 2014 Share Posted June 3, 2014 I don't have a clue when it comes to voltage, soldering etc. But I really want to have the power LED in my 7800 changed out. What I would like is a "Rainbow" LED that would slowly cycle through the colors, and kinda go along with the lines featured on the 7800 console and start up screen. Anyone know if something like this would work? http://www.411techsystems.com/Rainbow-Flashing-5mm-LED_p_40.html Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted June 5, 2014 Share Posted June 5, 2014 I don't have a clue when it comes to voltage, soldering etc. But I really want to have the power LED in my 7800 changed out. What I would like is a "Rainbow" LED that would slowly cycle through the colors, and kinda go along with the lines featured on the 7800 console and start up screen. Anyone know if something like this would work? http://www.411techsystems.com/Rainbow-Flashing-5mm-LED_p_40.html My guess is yes that would likely work just fine. And after thinking about it, most of the original LEDs were roughly 5v or 3.4 variants to begin with. So the limiting resistors being talked about likely already exist on the boards those LEDs are soldered into. That would explain why all the ones I've done are still going strong today. Quote Link to comment Share on other sites More sharing options...
Dauber Posted April 1, 2017 Share Posted April 1, 2017 Sorry to resurrect this oldie (hey, could have done this to CPUWIZ's 2002 thread ), but...I got an AV mod that surprisingly came with one of those "rainbow" LEDs, and I think I want to go ahead and put that sucker in. Only thing is...there were no instructions, and I can't find anything online. Which way does the light go?? Want to make sure I arrange the long pin and short pin correctly. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 1, 2017 Share Posted April 1, 2017 Okay...if you have a meter, then the easiest way to know is to find out which hole on the mainboard is attached to ground. That will be the negative leg or shortest leg side. The longest leg is the + or anode side of the LED and needs to be attached to the +voltage. So again, using a meter, one of the two holes the legs where going into, will beep on ground and that is the negative side. Quote Link to comment Share on other sites More sharing options...
Dauber Posted April 1, 2017 Share Posted April 1, 2017 And therein lies the problem: my multimeter decided to give up the ghost. Argghrhh... Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 1, 2017 Share Posted April 1, 2017 Gotcha...well.. I don't have my 7800 apart right off hand to tell you for sure. But if you setup a temporary connection with it that you can easily connect/disconnect, then you could just plug it in and when you press power if it lights up...you're good. If not, then quickly turn power off and reverse. I've done that...quite a few times... Quote Link to comment Share on other sites More sharing options...
iesposta Posted April 1, 2017 Share Posted April 1, 2017 Great idea using a color changing LED! I put a mini blue IN the 2600 power switch. It's too bright, and if the console is in front of you as intended (12-15 ft RF cable!) the switch angle shines right in your eyes! So I should add more resistance? Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted April 1, 2017 Share Posted April 1, 2017 How large is the resistor you have on it now? Usually something along 100 - 150 ohms is more than enough in most cases. I do have a calculator for this, but it usually wants some odd ball value to be used. So I usually start with at least 100ohms and then either decrease or increase as needed from there. Quote Link to comment Share on other sites More sharing options...
iesposta Posted April 1, 2017 Share Posted April 1, 2017 How large is the resistor you have on it now? Usually something along 100 - 150 ohms is more than enough in most cases. I do have a calculator for this, but it usually wants some odd ball value to be used. So I usually start with at least 100ohms and then either decrease or increase as needed from there. Don't remember it was years ago and I used 2 scrap resistors in series right off the 5V regulator. LED was also scrap, so I didn't know needed Voltage. The picture of it lit was a 1.5V button battery and that was dim. Quote Link to comment Share on other sites More sharing options...
Osgeld Posted April 1, 2017 Share Posted April 1, 2017 More resistance less light led s are current driven Quote Link to comment Share on other sites More sharing options...
Osgeld Posted April 1, 2017 Share Posted April 1, 2017 (edited) ok now that I am back home, lets have a (simple) crash course on LED's Voltage: All diodes have a forward voltage, you must meet or exceed this voltage before the diode will start conducting, so if your LED has a fV of 2 volts you must provide at least 2 volts before the junction inside the LED starts to conduct, and thus light up, you can exceed this voltage, and its very common to as well Current: Current is what you want to pay attention to, you can pretty much guess that any dumb old though hole LED found anywhere is going to max out at 20ma (0.020 amps) if you exceed the current rating of the LED it will shorten its life, depending on how much it could take years or it could just pop and fizzle, if you go below the current rating of the LED, it simply wont put out as much light as it potentially could This is not a linear function ... IE half the current doesn't mean half the light Resistance: This is the simplest way to control how much current is passing though the LED is with a resistor, and you can calculate how much you need by (Vin - Vled) / current so if Vin is 5 volts minus a Vled of 2.1 volts = 2.9 volts ... 2.9 / 0.02 = 145 (ohms) or for a blue or white LED which usually hovers around 3.1 volts for 20ma you would need 100 ohms Are you safe to swap a red led already in something for a blue or green or neon pink, pretty much yea Edited April 1, 2017 by Osgeld 3 Quote Link to comment Share on other sites More sharing options...
Dauber Posted April 2, 2017 Share Posted April 2, 2017 Well, taking a chance, I desoldered the LED, and found that it was actually pretty obvious which way to orient it. Color-changing LED works great. Quote Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.