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heathkit part help

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wltomlinson

New Member
hi. newbie here.
need an interchange for the light-bulb used in the feed-back circut in a vintage Heathkit IG-18 signal generator. old one is smashed.

thanks
bill:confused:
 

Willbe

New Member
They used a 3w lamp in the HP 200 version, which was barely visible in a dark room.
The Heathkit lamp was much less wattage and was not visible. It looked to be the size of a neon lamp.
 
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Leftyretro

New Member
That is going to be a hard one to figure out. The manual I found on line didn't give a generic part number, just Heatkits internal number. Appears to be some kind of tunstan lamp. Further goggling turned up nothing. It's used as the ALC element of the oscillator so it's resistance Vs voltage is it's critical spec and as such not subject to just trying any old low voltage lamp.

Lefty
 

mvs sarma

Well-Known Member
What is the Heathkit Part number?
the lamp is like the older switch board lamps used in telecom as indicator. Any bulb of say 8V/60mA would serve the same purpose, I feel. Even a PTC resistor would suffice if carefully enclosed.
 
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mvs sarma

Well-Known Member
This guy
http://www.angelfire.com/electronic/funwithtubes/IG-18_Mod-B.html
must know what that lamp was/is.
Click the "home" button on the bottom.
Below the block schematic of the link, there is a click button, that has revealed info listed below.

" Simplified diagram of the twin T lamp stabilized oscillator. No component values are given. The amplifier is represented by a triangle with the point to the right. The output is on the right and the two inputs are on the left. The output goes through a tungsten lamp to the non-inverting input. The noninverting input goes through a resistor to ground. The output goes through a capacitor to the inverting input. The output goes through one resistor, then another resistor, to the inverting input. The junction of the two resistors goes through a capacitor to ground. End verbal description."
 
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