Still wrestling with IG-72

[Dave]

Hello again,

This stubborn thing!  You'll recall my query about the
115v 3-watt bulb in the oscillator circuit?  I have now
replaced it with the closest possible match I could
find - 115v 4-watt.

But STILL no oscillation.  The suspect paper electrolytics
near the 6AU6 have been replaced, and the tubes are
all good.  This silly thing SHOULD oscillate.

Could my light bulb be too far out of whack?  I measure
238 DC Ohms on it.  But it appears to me that the 600 ohm
pot to ground in the cathode circuit of the 6AU6 should
provide more than ample balance of the voltage divider.

Any ideas?  The only value part I have changed is the cap
from pin 7 to pin 6 of the 6AU6 - I used a 22 MFD in place
of the 15 MFD original - the only value even close that the
parts house near me had in stock.  The old one is definitely
shot, so I can't put it back to test.

C'mon you closet IG-72 wizards!

73

Dave WB7AWK
http://www.boatanchors.com

Sponsored by the City of Tempe 

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