Please help me identify a few resistors - Page 1
Forum section: electronics / beginners

author: jpyerry
author_rank: Newbie
timestamp: January 18, 2013, 11:58:56 pm
content: Hi guys,I was hoping you guys might help me identify a couple resistors. Normally I wouldn't bother you with a simple question like this, but after looking at the color codes, I just can't make heads or tails of these resistors. For instance the one five band resistor: orange, blue, black, silver, green, I calculate should be 3.60 ohm with a tolerance of .5%. After doing a parts search, it appears that nobody even makes such a resistor. I don't know, maybe I am color blind and am just finding out, but I would really appreciate some help with this one. I have attached some pictures to help.Like I said, I really hate to trouble you guys with such a simple question, but I would really appreciate some help with this.Thanks in advance,Justin

author: notsob
author_rank: Frequent Contributor
timestamp: January 19, 2013, 12:45:12 am
content: Perhaps you should get yourself a multimeter, to aid you in learning resistor colour codes.

author: PA4TIM
author_rank: Super Contributor
timestamp: January 19, 2013, 12:48:10 am
content: Why do'nt you measure them ? Then you know. The first looks what you think. In measurement stuff I find the strangest values. Sometimes it also can be inductors or diodes.

author: jpyerry
author_rank: Newbie
timestamp: January 19, 2013, 01:39:55 am
content: Alright then,To answer the first reply, I do own a multimeter, a Fluke 189.I have measured them, but since I am trying to troubleshoot a malfunctioning piece of electronics, I would like to know what the expected values of each of the resistors are, so I can measure and figure out if they are out of specification.So, for the one five banded one, my meter measures its resistance as 3.7 ohms, and if the tolerance on this resistor is 0.5%, then the resistor is out of specification, and I would want to replace. But, a cursory search on several vendor sites indicates that a 3.60 ohm resistor with a tolerance of 0.5% seems to just plain not exist and I am wondering how this can be.The brown, green, brown banded resistor with gold tolerance band, I calculate to be 150 ohms with a 5% tolerance. My meter measures it to be 146.62 ohms, so I conclude that one is within tolerance specifications.The brown, black, yellow banded resistor with gold tolerance band, I calculate to be 100 kiloohms with a 5% tolerance. My meter measures it to be 102.1 kiloohms, which would be within 5% tolerance.So that leaves the last two resistors. The resistor that is banded gold, silver, black, with a brown tolerance band measures to be 0.23 ohms. The resistor that is banded gold, silver, green, with a red tolerance band measures to be 0.37 ohms. But, my issue is that according to the charts that I have read, gold and silver being either the first or second bands seems to be non-sensical, so I don't have a method to calculate what the expected values of either of these resistors should be and thus have no way of verifying that they are within their specifications.So, really my question boils down to whether or not I am reading the 5 banded resistor correctly, as a 3.60 ohm 0.5% tolerance resistor does not seem to exist? And, secondly, having gold or silver as the first or second band doesn't make sense, so how should I interpret those markings?I just really need help with those three resistors.Yours,Justin

author: mark-r
author_rank: Contributor
timestamp: January 19, 2013, 01:42:08 am
content: My guesses are:3.6 ohm 0.5% (a preferred value in the E24 range)0.1 ohm 5%100k 5%Odd one, might not be a resistor if the CM8 legend refers to it150 ohms 5%, might be 1.5k if the multiplier looks more red in real life.

author: jpyerry
author_rank: Newbie
timestamp: January 19, 2013, 01:58:22 am
content: Quote from: mark-r on January 19, 2013, 01:42:08 amThe CM8 is referring to an unpopulated capacitor (I believe), it is obscured in the picture but, the legend has this component labelled RM816.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: January 19, 2013, 03:27:05 am
content: Hi,The silver band in the multiplier position means divide by one hundred or multiply by 0.01(A gold band in this position means divide by 10 or multiply by 0.1)SoBrown Black Silver Goldis1 0 /100 5% = 0.1 Ohm 5%andRed Green Silver Goldis 2 5 /100 5% = 0.25 Ohm 5%This is consistent with your meter readings if you allow about 0.1 Ohms for lead resistance.I think all the resistors are good. They would be discoloured if they were bad.Regards,Jay_Diddy_B

author: PA4TIM
author_rank: Super Contributor
timestamp: January 19, 2013, 08:03:06 am
content: I could not see the colours good enough on this device so thst is why I aked if you could meaure them. If I knew why i knoe now my answer would be different.- for very precise measurements do not meaure in situ- under 10 Ohm you relly need 4 wire technic- zero your meter, meaure the value. Look up the accuracy specs for the meter ( % and % of full scale or counts) and calculate the deviation of the meter and see if the wanted value its within.Tenths of an Ohm is nothing, just clipping your kelvin clips a bit tighter can cause 0.05 Ohm difference but you do not use clips so the effect can be more. The tempco of the resistor place a role ect ect.Now knowing your Measured values and looking how the resistors look I eould say they are not the problem.If they use 0.1 % or 0.5 % the value is critical indeed, but your methode of measurement not suitedIf they use 5 % resistors it does most times not matter very much it the deviation is a bit bigger, but sometimes it does. The schematic , the symptoms and your calculator will tell you ( most times)Are you just meauring all conponents or is there a reason you suspect these resistors. ( so shotgun repair or conclusion after measurement evaluation leading you to these resistors.)

author: jpyerry
author_rank: Newbie
timestamp: January 19, 2013, 11:05:43 am
content: Quote from: PA4TIM on January 19, 2013, 08:03:06 amThis device comes from LCD TV, it is the power supply board. The TV does not turn on anymore, the power LED just flashes. I read that this can be caused by faulty capacitors, I don't own an ESR meter, so I just replaced all the electrolytic capacitors with new ones with specs that met or exceeded the specs of the original capacitors. The repair did not remedy the problem.So, now I am attempting to measure all other components to see if they are problematic. I was lead to the resistors, because I read on a forum elsewhere that somebody who experienced similar symptoms on a similar TV found and replaced a bad resistor and that fixed the problem, which is why I am trying to test the resistors.But, if it sounds like the resistors are within tolerance, I'll start looking into other components.Well, I am leaving the area for the weekend, so I won't be responding to any replies until Monday.Thanks for the help.Justin

author: grumpydoc
author_rank: Super Contributor
timestamp: January 19, 2013, 11:11:28 am
content: QuoteI must admit I find myself sympathising with the inability to decipher resistor colour codes these days - E12 is fine but increasingly for E24 I find that red, orange and brown are barely distinguishable, silver and gold look more like (or are substituted with) white and yellow and the supposedly slightly wider band before the tolerance is the same width as all of the other gaps.Not quite sure if it's my eyesight or how the things are marked but I resort to a multimeter to check far more than I used to.

author: dr_p
author_rank: Frequent Contributor
timestamp: January 19, 2013, 03:33:32 pm
content: Quote from: jpyerry on January 19, 2013, 11:05:43 amAnother common fault is an over-current situation where the PSU constantly goes into OVC protection. Measure current draw. If it's so, unplug (if possible) or disconnect the inverter board. If the problem goes away, the inverter is at fault. While not powered, measure resistance of the output high voltage transformers. They should be of the same order of magnitude. If one is way off (short) that that's what is causing the over current situation. It's unlikely they both failed simultaneously. Good luck with that!

author: jpyerry
author_rank: Newbie
timestamp: February 16, 2013, 01:04:30 am
content: Hi guys,I never posted a follow up to my inquiry. After reading through the responses, I ran a few more tests, replaced a few more components on PS board of the TV and still couldn't fix the TV. So, I started wondering if the fault was elsewhere, and so I changed out the mainboard yesterday, the TV fired right up. I feel like an idiot for not trying that earlier, but I really thought the problem was with the power board, I suppose that at the very least the PS board no longer has junk Samyoung capacitors and now has reputable brand capacitors on it. Good learning experience all in all.Yours,Justin