Tested Gauge Clusters

[mudnut]

I am enjoying this little hobby and the challenges that have arisen. It has been an eye opener and there is so much to learn.


I need to get good, clear pictures of the front and back of all the different styles and models of the GQ clusters. TB42, TB42E, TD42, RD28, RB30, Turbo, Autos and Manual transmissions etc.

So, If you have a spare cluster, or have a need to remove your cluster for any reason, please take some shots and post them up for me.

Thank you in advance and cheers, mudnut.

[mudnut]

Okay, fellow Patrolians, I have had to wait for the local electronics store ship in an electronic metronome kit. I built the kit, then set about modifying it to run on 14volts and produce a square wave instead of a pulsing beat. I had limited success and the tacho read 3000 rpm until the second hand transistor I used as an input, destroyed itself and the metronome circuit seemed to suffer form some sort of feedback or distortion at above 350/ 400 Hz. I have used a 555 timer instead (From an old egg timer I made in the eighties). From what I can see the tacho on my Old Trol uses an input of 9-10 volts and between 200/ 600 hz and 446 micro amps. I need to order some transistors online and some advice on which type to get would be appreciated.

[BillsGU]

You could use a 2N3055. It is an NPN and should be able to handle the power required. It has a T03 case so it can be bolted to a large heat sink if needed. The transistor in the circuit seems to be used to amplify the output of the 555. You just need ot make sure that the emitter resistor you select limits the current to below the maximum current as per the transistor data sheet. Download a data sheet for the 3055 and it will give you typical values. You may also need a couple of base bias resistors to set up the Q point at the output to give you the swing you want. The idea would be to do some calculations and then bread board it using variable resistors until you get it exactly right.

[mudnut]

Thanks, Bill, your info gives me a starting point. I reckon the transistor I used must have been damaged by heat when I unsoldered it.

[nissannewby]

Mudnut.

Excuse my laziness for not reading back. Do we get a square wave signal at any part of the system?

[mudnut]

Yes, Matt. The tacho input is a very messy square wave with a 9 volt bias. (or so my scope reads that)

[BillsGU]

Yes, Matt. The tacho input is a very messy square wave with a 9 volt bias. (or so my scope reads that)

Do you mean the centre of the square wave is at 9 volts, or the bottom of the square wave is at 9 volts ?

[nissannewby]

Yes, Matt. The tacho input is a very messy square wave with a 9 volt bias. (or so my scope reads that)

Cheers mate. I have an electronic boost controller that can use rpm for boost correction and requires the use of a Square wave signal for its input. I think it's range is 3-12v.

[mudnut]

This is a picture of the tacho signal across the 2k resistor to earth under the bonnet of my RB30, Matt. It shows the approximate voltage of 7.8 volts to earth, a frequency of 332 Hz and the messy square wave. It doesn't show the high spikes with each wave very well, so be aware that they may influence the device you intend to run. The system also draws approximately 440 microamps.

[mudnut]

Do you mean the centre of the square wave is at 9 volts, or the bottom of the square wave is at 9 volts ?

The first couple of times I hooked up the oscilloscope the square wave was about 1.5 -2.0 volts at the top of nine volts dc. That is why I said a 9v bias. Today my scope shows a square wave as just a 7-8 volt wave (peak to peak) to earth. I have no idea why it has done this as I haven't changed the parameters. I am still struggling to understand the chinese instruction manual.

Edit: Maybe early on, I measured just across the resistor and not from the yellow black to earth??