How do you test a converter/charger 7400 series 7440 model to see if it works?

Hi. Thanks for your question.For any information you can visit https://www.reliable-store.com and download the entire workshop manual which includes all the information along with the diagrams for better understanding. Good day!

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The component vendor for RT1 is US Sensor Corp, part # ST2R018B.

Minimum Supported Red Hat Updates •Red Hat Enterprise Linux 5 Update 1 •Red Hat Enterprise Linux 4 Update 5 6-Core/4-Core Intel Xeon Processor 7400 Series •Red Hat Enterprise Linux 5.22 •Red Hat Enterprise Linux 4.7 Minimum Supported Novell Service Packs•SUSE LINUX Enterprise Server 10 SP1•SUSE LINUX Enterprise Server 9 SP31 6-Core/4-Core Intel Xeon Processor 7400 Series •SUSE LINUX Enterprise Server 10 SP23 •SUSE LINUX Enterprise Server 9 SP44

You can get one almost anywhere. www.amazon.com
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and more.

Unplug the dryer.
Remove the back panel.
Inspect the wires at the terminal block where the cord connects.
With a volt meter set for continuity check the thermal fuse on the heater canister(up high). No continuity , replace it.
Check the hi limit thermostat at the heater terminals, no continuity , replace it.
Check the heater terminals for continuity. If none replace the heater.
Remember to remove at least one wire from each part before testing.

bought a used non-workjing dx 7440 camera for cheap on ebay and just took mine apart and replaced the rear housing assembly. the solution to the parts problem was googling it and finding some ebay matches that were hard to find on ebay's site itself ...

it's alway suggested that you simply use plug adaptors to change shape of plugs for overseas-do not reduce voltage since most all chargers including yours support 220 or 110

where are you what country,? (matters for language and keyboards)
wow, compaq relic day' from the PENTIUM 2 days,a relic !
no exact PC stated, the full model number. just a series
no OS stated, XP? what?
possible wrong can be 3 things,

1. bad keyboard.
2. (or wrong kbd for you country)
3. or unstated windows set to wrong country;

first off the 7400 has many sub models stated on your service tag
page3
https://www.manualslib.com/manual/926638/Compaq-Armada-7400-Series.html?page=3#manual

for example 7400-6300
there is even a code for the many keyboards used world wide.
page 4 states
Euro symbol provided on Europe/Middle East/Africa keyboards
this old pc even has 1 USB jack on the rear
try a USB KEYBOARD there yet> see if it works ok?
that be first thing Id have done, to see if its hardware or software issue.

this pc came with O/S ,win95 , win98 or NT
you never said what? OS

will not print the colour magenta,have cleaned many times, and have changed carts.