Replacing burnt parts in tachometer

[E Sully]

When I changed out the odometer gear I photographed it last year.

[village idiot]

I saw Warren's thread while searching for answers, but it was a bit technical for me as they were discussing wave forms and other things that were way over my head.

porwolf, again, that was an excellent(educated obviously) guess.

Ed, thank again for the pic and info. Looks like I have a little electrical experiment to perform this weekend.

[rick-l]

Anyone read German?

the bigger pdf file

SAY115 datasheet and application note, data sheet, circuit, pdf, cross reference, pinout | Datasheet Archive

[rick-l]

That 47 uF 16 volt capacitor may be shorted out also.

[rick-l]

EDIT: Never mind..... Realizing it was a speedo and not a tachometer I can see the similarities to a UAF2115

ok what does endstufe mean? schalllung? stromquelle?

[porwolf]

Here is a translation of rick-1's diagram. Also:

"Endstufe" = End Stage
"Schaltung" = Circuit Diagram
"Stromquelle" = Current Source

[porwolf]

Hi "village idiot" (Obviously NOT!!!) thanks for the compliments. Keep enjoying the Aloha state like I did visiting wise for years:

[porwolf]

Forgot to include Hawaii picture. We all like pictures. Here it is: Maui 1995

[village idiot]

Originally Posted by porwolf

Forgot to include Hawaii picture. We all like pictures. Here it is: Maui 1995

nice!!
I'm going to try fixing this thing tomorrow. Will post results(if positive )

[village idiot]

well, I did manage to replace the resistor as well as replacing the broken odo gear. Unfortunately, while reassembling the unit I managed to break the needle shaft........ oh well, at least the guys at parts heaven had one on hand for a c-note and it's on the way. Thanks again to all those who helped

[village idiot]

Got the new(used) speedo and installed it. No joy, still not working. double and triple checked the wiring. The only thing I seem to be missing is the white w/red striped wire, which, if I'm not mistaken is only used for cars with cruise control or o2 mileage counter which I do not have.

I used an oscilloscope to check the trans-mounted sensor and it is producing a square-wave signal that changes in relationship to wheel speed. I'm stumped....................

HALP!

[porwolf]

Hi Tom,

you are really lucky with those speedometers!!! Looking around Pelican threads I found this one:

VIDEO How to test a Speedometer

Could you do that test in the video?

Wolfgang.

[village idiot]

Originally Posted by porwolf

Hi Tom,

you are really lucky with those speedometers!!! Looking around Pelican threads I found this one:

VIDEO How to test a Speedometer

Could you do that test in the video?

Wolfgang.

Wolfgang, I didn't need the test rig as I just swapped the speedo into my 88 Carrera and went for a drive. In that car it worked fine.

I am 95% sure I have the wiring correct so now I'm thinking the sender is at fault. I just can't bring myself to order a new one from our host for $150 on a hunch.

Tomorrow I'll pull the sender and check it out.

[village idiot]

HAHAHAHHAH!! took the sensor out and cleaned it as well as the "well" that it sits in. Also made sure the sensor was oriented in the well. Took it out for a spin, and to my surprise it worked!!
Not 100% perfect though, as it seems it reads a bit high. Oh well good enough to pass inspection.......Now on to the inop tach.................

[Omegaman]

Very useful info here, helped me fix my speedo. I had an open circuit 1n4148 diode and leaky 47uf 16v capacitor. Speedo swings full range at 12v 300HZ square wave.

Thanks!

[oarable]

Thanks for the pic E Sully. That is a great help!