Summary: Info request - Hamm. SP-600

Roy Morgan morgan at SPECKLE.NCSL.NIST.GOV
Fri Aug 22 10:32:07 EDT 1997

At 02:14 PM 8/20/97 -0700, John Mitchell wrote:
>Thanks to all who provided the requested info and advice about the SP-600.

I forgot one important piece of advice:

The SP-600, like all sets of its time,  was designed for 115 to 117 volt
operation: your line voltage is likely to be higher, as it is in most
houses today.  Mine runs 122 most of the time, with 124 not unusual.
Unlike the R-390 and R-390A, the SP-600 has tap on the power transformer
for 120 volt line operation (or is it 125 volts, even better).

Do your set a favor and CHANGE THE TRANSFORMER TAP!

For R-390 owners, and for many other sets the choices are:

 - Find a step-down transformer (some isolation transformers will step down).

 - Build an external voltage bucking unit with a filament transformer.

 - Install the voltage bucker inside the set.

 - Run a constant voltage transformer such as a Sola.  These things hum a
lot and get hot, but they provide current limiting protection.

(Details on the use of filament transformers for line voltage bucking in my
next post.)

Keep em Glowing!
Roy, K1LKY since 1959

-- Roy Morgan/Building 820, Room 562/Gaithersburg  MD 20899
(National Institute of Standards and Technology,  formerly NBS)
301-975-3254 Fax: 301-948-6213  morgan at --

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