[time-nuts] any experts at repairing WaveTek 288's?

Scott Burris slburris at gmail.com
Wed Apr 30 10:16:04 EDT 2008

I have done the test under power with a logic probe with no pulses 
either.  Nevertheless,
this looks like a mechanical encoder, see the attached diagram from the 
schematic.  Only
3 connections, ground, and two switch outputs.  The part is listed as 
manufactured by WaveTek.
Any standardization in the encoder market, i.e. if I can find an encoder 
that fits the circuit
board and the front panel dimensions correctly, is there a good chance I 
could replace this
with an off the shelf part?

I have to say I'm shocked to hear that optical encoders were made with 
light bulbs -- haven't
LEDs been viable since at least the early 70's?  Talk about planned 

RE the poor quality caps -- it looks like the electrolytics are all NIC 
or Panasonic, not a no-name cap.
Still, I've seen my share of balky electrolytics.  I was just hoping 
someone had fixed this particular problem
before and could point to a likely component to try first.


Didier Juges wrote:
> It is not clear from your post if you did that test while under power or
> not.
> This is probably a Rotary Optical Encoder. It may need 5V to power the LEDs
> or light bulb that activate opto-sensors, so you probably need power applied
> and use a scope to check the outputs. Also, some devices only generate short
> pulses on the outputs which will never show with a multimeter (I have a
> Kenwood radio that does that), you would need a scope. 
> If you do not get anything, it may be that the light bulb inside is dead.
> This is a common problem on HP gear of that vintage.
> Didier KO4BB 

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