How may I convert an older photo tach to a larger capacity?

[frank mccune]

     Hi All of you EE and electronic buffs:


     I have an older tachometer I would like to alter it to read higher values.  As it is now, it reads 2,400 and 12,000 rpms.  I would like to perhaps double those readings.

     This is a hand held tach that has a  photo cell to read light pulses. It has an analog meter to give  the readings.  The instructions in the case says that one puts reflective tape on the object to be tested.  Could I also increase the sensitivity with a better photo cell?  The meter has a pc board and is all solid state so it can't be too old.  It was manufactured by The Pioneer Electric and Research Corp Foresrt Park, Illinois

      As a gadget guru, I would like to get this thing working. 
   
      Anybody out there have any suggestion, or would like to play with this thing?


                                                                                             Stay well,

                                                                                              Franchi

                                                                         

[Rafael Gonzalez]

The sensitivity has nothing to do with it. The sensor sends pulses to a (old counter) set of flip-flops (old 74107's that divide the input pulses appropriately (digital) or, analog voltage through op amp. Then, the frequency is converted to an analog response (digital or analog) hooked up to the meter (analog). If you do not have a schematic, is like flying stunt with your eyes closed.   . BUY a new one. They are cheap. TH has them for prob. 20 bucks. If you want to tinker, get the schematic from the mfg. Not an electronic buff anymore. Retired EE, Sick of electronics...Fly R/C and C/L.
 WILL NEVER PUT RCVR IN A C/L AIRCRAFT .... UHGH!

 

[Chuck_Smith]

I'm so lazy now I use an audio frequency analyzer on my iPhone. It's a free app and it works pretty darned good. One less thing to drag around too.

[Howard Rush]

I'm so lazy now I use an audio frequency analyzer on my iPhone. It's a free app and it works pretty darned good. One less thing to drag around too.

Cool idea.

[Rafael Gonzalez]

Man!!! Did not know they had that! What's next...

 

How high is the response on it though...