[Test-Equipment] Heathkit IG-42 Signal Generator question

[chearn at widomaker.com]

Curt,

I have found much reduction of warm-up drift in inexpensive signal  
generators can be had my installing simple a half-wave voltage  
doubling rectifier off the 6.3 VAC line and then using either a Zener  
regulator or a 3-terminal IC regulator to get back to 6 Volts for the  
oscillator tube.  Also, adding some inlet and outlet ventilation holes  
is helpful in lowering internal temperature rise.

These two mods. can tame frequency drift in the older sig. gens (like  
the  mainstay URM-25D dramatically ; later URM-25 models added a Zener  
filament voltage regulator for the oscillator).  This mod. is also  
worthwhile, sometimes amazingly so, for boat-anchor tube receivers,  
AND it can be done reversibly, for purists.

For reducing microphonics, you can try sitting generator on a foam pad  
- it works!
                                                         Cheers, Chase

Quoting cparrish104 at cfl.rr.com:

> Is anyone aware of any mods for the Heathkit IG-42 Signal Generator?  
> Particularly in the areas of reducing microphonics and drift? My  
> still works but I think it has had these problems since the  
> beginning. Built in 1962.
>
> Thanks, Curt
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