do you have a pic. ????
Tach Filter: $2.57
Thread Starter
Intermediate
Joined: Aug 2004
Posts: 44
Likes: 0
From: Centennial CO
Tach Filter: $2.57
I just couldn't convince myself to spend $26 for one of those new looking tach filters. My tach hasn't worked since I bought my car, and the lack of movement on the gauge drove me crazy! I spent a couple of days researching the original filter, and I finally decided to raid the electronics store this morning... $2.57 and a few minutes at my workbench, then a couple seconds under the hood and I have a working tach! (WOOHOO!)
Here's a quick schematic for anyone interested in saving some money by building a tach filter themselves..
Coming soon: The poor man's clock repair...
Here's a quick schematic for anyone interested in saving some money by building a tach filter themselves..
Coming soon: The poor man's clock repair...
Last edited by Slink; Dec 13, 2004 at 01:36 AM.
Melting Slicks
Joined: Jul 1999
Posts: 3,030
Likes: 17
From: White Pine / Dandridge TN
I've never had a tach filter, yet my tack works. Lately the needle started to jump around...not sure why. Funny how the tach filter makes a difference on some tachs and not others. Can you post a pic?
Race Director
Joined: Sep 1999
Posts: 11,358
Likes: 379
From: Plano TX
Some work just fine without a filter. It's a combination of the specific tach and ignition module and coil. The module/coil combination creates ringing on the tach wire that many tachs see as a firing event so the needle jumps around or shows a reading that's too high.
MFD = micro farad. Yeah, a mega farad would be the size of a decent living room.
MFD = micro farad. Yeah, a mega farad would be the size of a decent living room.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
the correct notation for Fahrad = F and for micro it's the greek letter mu, since that's not available (or at least I don't know the code for it) most pople use a u since it's about the same as a mu, missing the longer leg. So uF would be the best notation.
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Thread Starter
Intermediate
Joined: Aug 2004
Posts: 44
Likes: 0
From: Centennial CO
Sorry guys, I thought it was obvious...
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Last edited by Slink; Dec 13, 2004 at 11:53 AM.
Thread Starter
Intermediate
Joined: Aug 2004
Posts: 44
Likes: 0
From: Centennial CO
Sorry guys, I thought it was obvious...
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Please feel free to clean up my quick sketch if anyone has the ability. I can when I go back to work, but that's not going to be for about a month.
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Please feel free to clean up my quick sketch if anyone has the ability. I can when I go back to work, but that's not going to be for about a month.
Last edited by Slink; Dec 13, 2004 at 11:56 AM.
Thread Starter
Intermediate
Joined: Aug 2004
Posts: 44
Likes: 0
From: Centennial CO
Sorry guys, I thought it was obvious...
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Please feel free to clean up my quick sketch if anyone has the ability. I can when I go back to work, but that's not going to be for about a month.
Anyway I neglected to take a pic but I'll probably be pulling it out this weekend to make a better looking version. Not that anyone would even see what's on the car, but I'm kind of a perfectionist when it comes to this kind of stuff and it's not up to my standards yet. I'll get some pics when I clean it up.
Please feel free to clean up my quick sketch if anyone has the ability. I can when I go back to work, but that's not going to be for about a month.
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
Originally Posted by Twin_Turbo
the correct notation for Fahrad = F and for micro it's the greek letter mu, since that's not available (or at least I don't know the code for it) most pople use a u since it's about the same as a mu, missing the longer leg. So uF would be the best notation.
used MFD to denote MicroFaraD. Sometimes it's tough to read old schematics.
Race Director
Joined: Sep 1999
Posts: 11,358
Likes: 379
From: Plano TX
Originally Posted by NHvette
YUP - but before the US went totally metric, electrical engineers
used MFD to denote MicroFaraD. Sometimes it's tough to read old schematics.
used MFD to denote MicroFaraD. Sometimes it's tough to read old schematics.
Race Director
Joined: Nov 2000
Posts: 16,416
Likes: 1
From: NC,USA
Originally Posted by zwede
The US is totally metric??? I wish... sure would make life easier to only have to remember ONE set of measurements.
I'm not particularly fond of the standard system... but not much that comes with a metric system intrests me.
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
Well, that comment was kind of tongue-in-cheek.
Note that all products are measured in the metric system.
Ok - it's the small print under the standard units.
I never said we were ONLY metric.
I don't thing any "inch" size hardware is used in autos any more.
I could be wrong - but most is metric.
Well, in Electrical Engineering, most is metric now-adays.
Anywaze .... If anyone is interested, I have done an analysis
of the behaviour of two proposed tach filters. The outcome
was to use the values (basically) in the schematic above.
Analysis: http://NHvette.com/ftp/in/NHvette_filter_comp.pdf
Note that all products are measured in the metric system.
Ok - it's the small print under the standard units.
I never said we were ONLY metric.
I don't thing any "inch" size hardware is used in autos any more.
I could be wrong - but most is metric.
Well, in Electrical Engineering, most is metric now-adays.
Anywaze .... If anyone is interested, I have done an analysis
of the behaviour of two proposed tach filters. The outcome
was to use the values (basically) in the schematic above.
Analysis: http://NHvette.com/ftp/in/NHvette_filter_comp.pdf
Last edited by NHvette; Dec 13, 2004 at 06:48 PM.
Burning Brakes
Joined: Oct 2004
Posts: 1,038
Likes: 0
From: Grants Pass Oregon
Standard?
I'm not particularly fond of the standard system... but not much that comes with a metric system intrests me. [/QUOTE]
We could express all demensions geometricly and use boulian math to size our nuts, bolts and wrenches..................
Course we might have three eyes and work from base 7 too....LOL
[/QUOTE]We could express all demensions geometricly and use boulian math to size our nuts, bolts and wrenches..................
Course we might have three eyes and work from base 7 too....LOL
Pro
Joined: Mar 2004
Posts: 584
Likes: 0
From: Okemos MI
Originally Posted by Slink
I just couldn't convince myself to spend $26 for one of those new looking tach filters. My tach hasn't worked since I bought my car, and the lack of movement on the gauge drove me crazy! I spent a couple of days researching the original filter, and I finally decided to raid the electronics store this morning... $2.57 and a few minutes at my workbench, then a couple seconds under the hood and I have a working tach! (WOOHOO!)
Here's a quick schematic for anyone interested in saving some money by building a tach filter themselves..
Coming soon: The poor man's clock repair...
Here's a quick schematic for anyone interested in saving some money by building a tach filter themselves..
Coming soon: The poor man's clock repair...
I made a tach filter tonight and it works great!
My tach problem was it was flakey, sometime it worked good and some times it would jump. I had to repair the wire several times. Vibration and heat from its mounting location on the intake takes its toll.
I built this very simple circuit and enclosed it in a radio shack Mini Project Enclosure drilled three holes for the wires out and mounted it to the firewall (see pic)
Attached you will also find a pic of the radio shack parts cards with the radio shack numbers to make it easy for anyone that wants a tach fix.
Try it its easy
Good Luck,
John
part numbers
10K resistor (pack of 5) 271-1126 $ .99
5.6K resistor (pack of 5) 271-1125 $ .99
0.1uf Capacitor (pack of 5) 272-109 $2.59
.01uf Capacitor 272-1051 $1.29
Mini Project Enclosure 270-288 $1.99
Pro
Joined: Mar 2004
Posts: 584
Likes: 0
From: Okemos MI
Originally Posted by Frankenvette
Lotus76,
any chance you can post a pic of the internals so we can all see exactly how you connected everything? Some of us are electronically challenged.
any chance you can post a pic of the internals so we can all see exactly how you connected everything? Some of us are electronically challenged.
