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

Didier Juges didier at cox.net
Wed Apr 30 20:49:40 EDT 2008

You can buy ROEs from companies like Avago (used to be the optical division
of HP).
They have relatively inexpensive models with up to 128 steps/turn. In many
cases (like my HP 3586A), more steps would be a very welcome addition. I
have obtained ROEs with 1000 steps/turn from a member on anothger list, but
I have yet to mount it (different shaft size, different mounting

Using a few gates, and if the circuit connected to the ROE lends itself to
it (fast enough), you can get 4 times the resolution from a given encoder
(essentially you get a full up or down cycle for every phase change in
output, and you get four discrete phases for every step). This requires a
small PWB or proto-board. My Kenwood transceiver uses such a scheme to
provide 1000 pulse/turn from an ROE with only 250 optical steps.

Alternately, you may be able to obtain one from another defunct instrument.
They are widely used on all sort of instrumentation made in the last 15-20

Didier KO4BB 

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Scott Burris
> Sent: Wednesday, April 30, 2008 9:16 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] any experts at repairing WaveTek 288's?
> 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 obsolescence...
> 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.
> Scott
> 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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