The Stovebolt Site Forums The Shop Area General Truck Talk I need a resistor - where/how to find electronic componets?

Hiyas folks.

So I have this tachometer out of my truck, it was in there when I bought it and it USED to work. I doubel checked the hook up again today and it still doesn't work - so I figured, it's broke anyway, I'll take it apart.

So I took it apart and started checking parts with the Ohm setting on a digital multimeter... found a busted resistor - took it off the board, still busted... so I figured I'd get a new one and install it - and maybe that is allt hat broke, maybe, maybe not but figured it was worth a shot.. one resistor is cheaper than a $45 dollar new tach.

So! Where do I get a resistor? I know back in the day Radio Shack sold that stuff, but the last time I was in a Radio Shack it seemed kinda slim on those type things. I figured I'd wander up there and double check anyway tho.

So, what would you electronic guys recommend I look under in the phone book?

Thanks folks,

-W

What's the resistance value? If it's color-coded, post the sequence of colors and somebody can tell you what size resistor to buy. Any electronics supply store should have them in stock, or a TV repair shop should have them, or know where to get what you need.
Here's the color code:
Black: 0
Brown: 1
Red: 2
Orange: 3
Yellow: 4
Green: 5
Blue: 6
Violet: 7
Gray: 8
White: 9
Silver: 10%
Gold: 5%

The first color band is the 1st. digit in the value, the second bhand is the 2nd. digit, the third band is the "multiplier", the number of zeros to add, and any other band is for tolerance. No tolerance band, there's a 20% tolerance, Silver band, 10%, Gold band, 5%.

Example: Red/Black/Yellow/Silver: 200,000 ohm, with a 10% tolerance. 20 X 10 to the 4th. power. Easy!

Now Here's the easy way to remember the color code: "Bad Booze Rots Our Young Guts, But Vermouth Goes Well" Or the classic: "Bad Boys Rape Our Young Girls, But Violet Gives Willingly, for Silver or Gold!"

Ain't electronics fun?

Jerry

From the above, the silver and gold bands are at the end?

With that line of thinking:


Yellow - Blue - Brown - Gold


4 / 6 / 1 / 5%

----

46 x 1 then how does the rest of the math go?

Update: AH! the 1 is the zero to add, I missed that part - okie dokie - 4, 6, add one 0 so we get 460 Ohms.

-W

You might try www.jameco.com I'm lucky, I have Norvac in town.

Woog,
you also want to get the wattage right, or at least not too small. If it is large, say about 3/4" long by 3/16" diam. it is probably 2 watts. The small ones are usually sroung 1/4 watt.

Radio Shack should have 470 ohm resistors for a buck, I don't know if that's each or twofer. Rediculously expensive, but cheaper than shipping.

I'd start at Radio Shack. The ones around here all have a cabinet or rack somewhere with this kind of stuff. I used to buy at Norvak when I did lots of this kind of stuff. But they may be a Northwest company.

I've also had good luck ordering from http://www.allelectronics.com/.

I think the third band is the number of zeros that follow the first two digits (its been a while I could be wrong). That would make yours 460 ohms.

47, 470, 4,700 and 47,000 are all common values. That gold band means 5% tolerance and that means that being 10% off in the value might be a problem. It might also mean higher tolerance parts than required were used. But I wonder why use an odd value if there wasn't a good reason.

AllElectronics lists a 1/4-watt 470 ohm at 50 cents, for 10 of them...

If it were me, I'd risk the 50 cents or a buck on a 470 ohm from Radio Shack and see if it works.

Resistors are cheap, and don't take up a whole lot of space.. so whenever I see them at a Hamfest (amature radio swapmeet) I buy 'em.. never know when you'll need one!

The 'Shack will probably have what you need in a "variety pack" with several other values for a couple bucks.. while expensive compared to what "real" electronics parts places charge, it's still way cheaper than buying a new tach.

I always buy my electical parts at www.mouser.com What an amazing selection! They'll have any resistance you need, with any precision and wattage -- and in just about any package type!

Brian

460 Ohms ( band colors break down to 4, 6, 1 and 5% so, 46 + one 0 equals 460, right?)

The resistor body itself, not the prongs - is right at 3/8's of an inch long.

The thickness is about 1 and a half to 2 times the size of a no. 2 pencil lead. <- we are so exact here with the closest tolerances here at the stovebolt page!



-W

"You learn well, young Jedi!" Yep, you've got the color code down pat, and a resistor that diameter is probably a 1/4-watt. It doesn't hurt to install a heavier-duty resistor, like a 1/2 watt or larger, just don't go too light on the power rating. Just scavenge up a 460 ohm resistor, break out the soldering iron, and drop it in there. Resistors aren't polarity-sensitive, so it can install in either direction. Good luck!
Jerry

Thank you very much everyone! I hope this is all that is broke, that would be neat.

-W

update:

So, I went and bought a 1/2 Watt / 470 Ohm resistor at radio shack and soldered it in good - wired it up - and the needle bounces and things but I don't think it is accurate - it'll go up to around 1500 rpm on the gauge while the tranny shifts (th350 auto tran/350 eng) so... 1, 2 , 3 and only 1500 don't look right to me...

mebbe it's picky?

Wrong resistor or sumfin' else is busted also.

-W

From the chevytalk.com thread:

http://www.chevytalk.org/threads/sh...3&an=0&page=0&gonew=1#UNREAD

Robert_May wrote:

You may have the wrong value in there. There is no 46x in the values. Try 360 ohms which is a 5$ value.
The colors on the resistors can be a bit tricky to determine. In addition, if the resistor is a 1$ value, there is an added digit to the value which means that there are 3 value bands and a multiplier vand. I don't remember all of the values of that system but I think that there isn't a 460 ohm value in that system of falues either.

----

hmn...

-W

Find somebody with a tach on a tune-up tester or a timing light, and compare readouts. So far as the comment about 3 number bands and a multiplier, I've never seen one like that, and I've been doing electronics work since the mid-1960's, for Uncle Sam and a few other employers. It might be possible, but you're more likely to find a chicken with lips!
Jerry

Well, if the "blue" band is actually violet, that makes it :

470 Ohms ( band colors break down to 4, 7, 1 and 5% so, 47 + one 0 equals 460, right?)

Which is what I have in there now... 1/2 watt

I just wanted to make sure my math was right.

Thanks a lot Hotrod Lincoln,

and everyone else also!

I love the 'Bolt!

-W