IG-72 Help!

[Neil Morrison]

The high voltage might be a sign that the tubes aren't drawing any
current. If the tubes have cathode resistors, measure the DC voltage
across the resistors as a guide to the current they are drawing. You
could carefully unsolder the cathode lead and run the unit with a
milliammeter/multimeter in series. They could be biased wrong, some
of the resistors may be off; or there may not be enough drive to the
tubes; or they may have little gain.

Regards,

Neil



----- Original Message -----
From: "Richard Bidwell" <rfb100 at CUISP.COM>


Hi group  --  I'm new to the list and also returning to tube-powered
radios and stuff after a lengthy absence.  As part of my
reincarnation I've gathered a bunch of Heathkit test gear to do good
things with.  This stuff has come from Ebay, and generally  it is
quite satisfactiory.  My current problem is a Heath IG-72 Audio
Generator.  The unit came in looking good and supposedly OK.  Well,
it ain't OK.  The output is very weak and really not usable.  I've
done all the good stuff like changing out electrolyics and paper
caps, checked all connection, and replaced all 3 tubes even though
the originals checked good.  This is far from a complex device but
I'm stumped.  The first obvious thing is that the voltages that the
manual gives are not what I see.  For example where voltage is
supposed to be 410, it is 550!  Mybe when it is working properly,
voltages would be correct.  I checked the power transformer and it
seems OK.  The transformer ratio is 10 to 1 with a center tap.  The
rectifier output is about 550 v. as noted above. This seems high.  Is
this normal for this unit? Any advice or guidance would be most
appreciated..  Cheers, Dick B.

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