====== Replacing Rotary Encoder Lamp on various HP equipment ======

//mikenearlibertymo wrote: // \\
//> I recently bought a couple units off ebay and one had no manual sweep // \\
//> or step functions. The problem was a burnt out grain of wheat lamp in // \\
//> the opto resolver. The lamps are same/similar to what you find in // \\
//> those "Mag" machined aluminum flashlights. I used a 6.3V unit to fix // \\
//> it. // \\

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If you are talking about the rotary encoder used for operator input on the front panel of many HP instruments of this era, the lamp is actually a grain-of-wheat coiled filament lamp rated at 5 volts. The exact replacement lamp is a type 683, available today from all the large supply houses. Failure is common and replacement straightforward, after getting the correct lamp.

Best wishes,

Larry McDavid W6FUB \\
Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)

//More information on September 23rd: //

If your encoder is the type with the removablel back cover its probably repariable.  I just finished repairing a couple of them for some HP 8660 sig gens.  They used a tungston lamp and a couple photo diodes internally.  Just replace the lamp test/adjust outputs, and you're back in business.

I purchased my lamps from www.KensElectronics.com for about $5.  

Mikenearlibertymo@yahoo.com

Mike