How Do You Remove The Needle From The Tachometer?

[wscheffer]

Hello everyone,

I have a W126 1987 420 SEL that has a faulty tachometer.

I removed the tachometer from the instrument cluster and found the burned out transistor. In order to repair it I must remove the face, but for the life of me I can not figure out how to remove the needle for the RPM.

The hands of the clock pull right off. Does the RPM needle unscrew?

If so which way?

I don't want to break it so if any one has ever done this that can tell me how I would greatly appreciate your input.

Thanks!

 

[television]

Ouch a hard one here, I believe that they are just a push fit, they may have a little glue, look through a magnifying glass look at the end near the needle to see if you can see any sign of any thread.

Best that I can do

 

[wscheffer]

Good thought I will try that.

Thanks Malcolm;

 

[television]

Let me know if you need any transistors, I have nearly 5000 in stock

 

[MIW615]

Hello everyone,

I have a W126 1987 420 SEL that has a faulty tachometer.

I removed the tachometer from the instrument cluster and found the burned out transistor. In order to repair it I must remove the face, but for the life of me I can not figure out how to remove the needle for the RPM.

The hands of the clock pull right off. Does the RPM needle unscrew?

If so which way?

I don't want to break it so if any one has ever done this that can tell me how I would greatly appreciate your input.

Thanks!

I repair antique clocks and come up against this all the time on the small French clocks - I purchased a small (1" in size") puller that would do the job. I see that you are in the US, you can easily purchase one of these pullers from a horological / clock supplier, just do a search on Google.

If you can't find a supplier I can give you the UK link - as I know they deal with the US

 

[wscheffer]

Can Not Identify Transistor

Is their a schematic of the tach listing the transistors and their location on the board. Reason why I ask is that the paint is no longer on the transistor that needs to be replace, therefore I can not identify it for replacement.

Thanks for the clock hand puller idea, but I used two table spoons and by applying an even amount of pressure with the spoons it gave me enough leverage to pull off the needle.

 

[television]

Sorry no such thing ever produced, since it is only a counter/ electronic voltmeter it will not be anything special.

It is doubtful if it ever had markings in the first place, this was done to stop people repairing them.

How do you know its gone

 

[wscheffer]

How do you know its gone

Because all the other ones still have the painted color stripes.

 

[television]

Because all the other ones still have the painted color stripes.

That is no way to tell, can you put a photo up

 

[wscheffer]

Tachometer & Transistor Pictures

Malcolm,

Here is a couple of pictures of the Tachometer & Transistor.

The one in question is the first one on the outer edge of the board next to the brown wire's connection to the board. This is if you were looking down from the top of the tachometer and the face facing away from you.

Thanks!

 

[television]

OK the bit that has gone is a resistor, now something has made it to burn out.

The resistor presents itself as a load to some other device on the board, and that device is drawing to high a current or is short circuit.

I cant do a complete electronics teach in here, so your best bet is to take it to a TV repair man who can measure the components cold, it will be hard to identify what the burnt out resistor value was, but it can be done by measuring a section say 1/3rd of the way in and multiplying by 3 so if a third of it is say for example 10kΩ multiply by 3 = 30, nearest preferred value = 27kΩ

As I said a tv man can work out why it burnt out

 

[wscheffer]

Malcolm,

Thanks I'll do that.