View Full Version : TV Output resistors values?

11-12-2010, 11:31 AM

For the TV Output on the PPDB, the resistors are 1100, 560 and 270.

I have thousands of resistors, but not those values :(

The closest I have are:
For 270 => 220 and 330.
For 560 => 330 and 470.
For 1100 => 1000 and 1200.

So my question is:
Can I go with 1000, 330, 220 instead of 1100, 560, 270? Or does those values need to be accurate?



11-12-2010, 01:05 PM
Just buy the right ones, they don't cost much. Of course, you could always build up something close by putting the ones you have in series and parallel; I think there is software around to do the sums for you.

11-12-2010, 01:08 PM
But if I buy some, I will not have them before Monday ;)

Do you have any link for a software able to help me with that? Else I will try to do some calculation.



11-12-2010, 01:25 PM
(2) 2.2k resistors in parallel will give you 1100 ohms. A 220 and 330 in series is 550 ohms which is probably close enough. Add another 10 ohm resistor in series , if you have one, to get a nominal 560 ohms. If you have any 100 ohm resistors, put one in series with (2) 330 in parallel to get 265 ohms, which is close to 270.


11-12-2010, 01:32 PM
I have 10 ohms, I have 100 ohms, I have 2.2k... Look like I have all what I need! Super!

I even have 1 ohms so I can put 5 in series for 265 ;) Or 2 x 10 ohms parallel.

Thanks. I will try that right away!


11-12-2010, 02:06 PM
It will work also with:
220, 470, 1000 Ohm

The values are not that critical, they just must build a 3 bit DAC, so the relation must be near to 1:2:4.
If you want it exact, use two 470 in parallel instead of the 220R.


11-12-2010, 02:11 PM
Ok! I see!

so I can you an R value with 2 R in parallel, 1 R and 2 R in series?

It's already too late, but if what I just did is not working fine, I will try that way.



Toby Seckshund
11-12-2010, 03:31 PM
As long as you are not trying to make some sort of test generator then as close as possible will be ok. I have always used 220, 470,1k2 as I usually only have E12 series resistors here.
Usually it is one of those bags of 600s, 10 of most values.

11-12-2010, 03:47 PM
I just figured my mistake :(

I'm using this breakout board: http://www.sparkfun.com/commerce/product_info.php?products_id=8826 and there is 3 pins. I thought BRL and BRK are the same so just choosed one randomly.... Wrong choice :(

So I'm back with the solution Lev proposed since I already soldered it and it's now working fine.

Thanks all for your help.


11-12-2010, 04:45 PM
Finally, it's not working ;)

It worked for 30 seconds then the display stopped.

I just plugged back the option with the 5 x 470 and seems to we working fine (way longer than 30 seconds).

So back to the soldering iron. Just to bad I already soldered the RCA Jack to the breakout bord, else I will have make my own board with it.


11-12-2010, 10:40 PM
Phil is the expert here, but I would thave thought 222, 470, 1000 would have been close enough. However, from Phil's comments in other threads, some monitors cannot handle a non-true 75 ohm impedance. He suggested a resistor and capacitor across the output to ground. IIRC 191R and 100pF. So I would try a 220R (which you have) across the output ans see if that helps.

The other possibility is that the TV program is not tuned correctly, or you are outputting NTSC to a PAL monitor. You may have to tell us what code you are running.

11-13-2010, 12:03 AM
I used 470 resistors.

2 in //.
1 alone
2 in serie.

The screen is now on for hours and working fine. Just the colors which are a bit different than from the PPDB but I will adjust that on the software side. So so far I'm fine with the result ;)


Phil Pilgrim (PhiPi)
11-13-2010, 12:14 AM
If your colors seem a little washed out (and they probably will be with those values), you can also add resistance across the final output terminals. I'd try a pair of 470-ohm resistors in parallel. See here:



11-13-2010, 01:26 AM
Very interesting! It's to late for the board I did, but I will keep that link.



11-13-2010, 09:09 AM
Thanks Phil. I knew it was your baby but didn't have time to find the link.