To DVH Group,

Important information about use of the Ithaco preamps:

The 1201 Ithaco preamps (the black differential preamps) should be plugged 
in at all times.  They have batteries that allow them to be run unconnected 
from the AC line to reduce 60Hz noise, but the batteries also help to 
stabilize the output.  When plugged in and set to charging (the normal mode 
--- middle position on the rear switch), they will constantly charge --- 
the battery LED indicator on the front should light on both polarities when 
they are properly charged.  I even prefer they be left on to keep them 
warmed up --- that reduces dc drift --- but at least they should always be 
left plugged in.

We have six of these.  I found yesterday that several were NOT plugged in 
and only one shows a proper battery charge.  Some may recharge in time, but 
the batteries may need to be replaced --- that was last done in 1995 by 
Brian Yanoff.  The batteries do eventually go bad, but their failure is 
accelerated when they get completely drained.  The batteries are probably 
$300 each to replace.

We have quite an investment in these --- they are about $2500 each --- and 
we rely on them a lot.  They are instruments we really want to keep 
functioning properly.  Please help to maintain them and report any 
malfunction so we can get them working well.  FYI, they are now 
made/maintained by DL Instruments (Ithaco no longer exists) --- the data 
sheet is here http://www.dlinstruments.com/products/pdf/1201.pdf .

Dale