Heath/Hickok/ Sine/Square wave-Hewlet Packard 400+

[Fred Olsen]

>  Hickok Teaching Systems HTS 81.
> 1.  What might the heath model number be??
Gordon, if I recall correctly that is indeed a Heath, an IG-82.

> 2.  Is the 3 watt lamp proper ...
Yes.  It should be a 3S6120V.  They are still available commercially.  A
seven or 10 watt lamp will get it going but the frequency response will
be compromised.  Think of a tungsten lamp as a nonlinear resistor.  In
normal use it runs below incandescence and should never burn out.
On these older units (and on others using the same scheme, such as the
HP 200-series) I'd suggest bonding the socket contacts to their
terminals by soldering.  Remove the lamp first, of course, and
thoroughly deflux after.

> 3.  Is there a schematic available??
Sure thing.  Thanks to Ken Grimm it's on BAMA.
ftp://bama.sbc.edu/downloads/heath/ig82.gif/

> Is the schematic and alignment info for the HP 400 C and HP 400D
> voltmeters available on the net like the Heath items are.
The only HP 400-series manuals which I know are posted are on the Army
LOGSA site, the dash 15 for the 400D/H/L;
Go to:
http://www.logsa.army.mil/etms/find_etm.cfm
and under "TM Title Text" search for 400D.
(The same one is on BAMA at:
ftp://bama.sbc.edu/downloads/hp/400/hp-400.pdf )

and the Air Force T.O. version of the same is also on line but the
bookmark escapes me at the moment.  Get back to me if you wish and I'll
try to find it.  Some of the scans are much better than the Army manual,
and it also has some backdating information, but it doesn't have parts
lists.  It's also in PDF.

Note that both of these are for fairly late S/Ns and don't cover the C
model at all.  As always with HP, Tek, et al, it is essential to have
the correct S/N coverage to reduce confusion.

Remember that these meters have a fairly wide frequency response.  DO
NOT diddle the attenuator trimmers unless you're sure of the flatness of
your source.  Trying to set the freq response against the average IG-82
would be a matter of calibrating the wrong instrument, especially using
an IG-82 with compromised response due to the wrong lamp.

Also, the tube used in the V1 position is aged and selected for low
noise and microphonics.  It was a separate HP part number from the rest
in the string.  This is more important for the H and L models but is
worth noting for all.

Watch out for a bad selenium rectifier in the DV heater circuit.  The
usual considerations of filter caps and split "Black Uglys" also apply.

Good luck,
Fred
-----
<><
-----
Outgoing checked by Norton AV

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://interactive.tempe.gov/archives/HEATH.html