[ARC5] RC-54-A, RC-55-A Test sets....

[Michael Hanz]

Well, it would depend on what the final series resistors are on your 666 
ohm/volt meters.  If I haven't made a silly error (which I don't rule 
out for a second), a couple of calculations might be in order:

On the five meter test sets,  the original input voltage meter 
(0-30vdcFS) has a load on the 28 volt circuit of  1,860 ohms, so its 
load on the robust 28 volt supply line is only ~15mA - a pittance on the 
28 volt supply line.  With your 666 ohms/volt meter, it would only be 
1.4mA - a fraction of a pittance.

On the screen and plate voltage meters using the 666 ohms/volt meters, 
the 500vFS meter would present a load of 333K, with a load of 0.9mA at 
the advised CW high nominal screen voltage of 310 volts.  The 750vFS 
meter would present a load of  about 500K, with a load of 1.1mA at the 
highest advised nominal plate voltage of 560 volts.  Compared with the 
_slightly_ less current draw of a 1,000 ohms/volt meter, I don't think 
those current draws would significantly affect the accuracy of your 
readings, frankly.

So, I guess I would worry about it too much.

- Mike  KC4TOS

On 4/6/2020 10:48 AM, Craig via ARC5 wrote:
>
> Hi Mike: Thanks for the additional info. The manual that I have a copy 
> of is the one revised in July of '56.  The reason for wanting better 
> photos, was to read the specs off the voltmeters. I've found that the 
> loading specification changes from version to version. I was able to 
> determine that the voltmeters on the panels were 1000 ohms per volt, 
> while the couple that I have found so far were 666 ohms per volt. 
> Dealing with the voltages in these radios, I would be concerned that 
> the lower spec meters would have a propensity to load the circuits 
> enough to cause problems.  I've got one meter on the desk now and two 
> more enroute and in the hunt for the others.
>
>
> Craig KF5JOT
>
>
>
> On 4/6/20 9:06 AM, Michael Hanz wrote:
>> The great cell phone snapshots that AB5S posted of the test sets 
>> reminded me of a long delayed project to expand and update a web page 
>> dedicated to the "five Weston meter" test sets.  Please note the 
>> drawings are hard to see on a cell phone - a desktop screen of 24" is 
>> ideal.  If you are so inclined, it is located at 
>> https://aafradio.org/docs/ARC_Test_Sets.html
>>
>> I included a reminder that all earlier _transmitter_ test sets have a 
>> different connector from the AN/ARC-5 transmitter test set, but the 
>> earlier ones _can_ be used with appropriate cable connectors on each 
>> end and a wiring change within the two cables.  Luckily, once made, 
>> the "adapter" cables can only be used with an ARC-5 set, so nothing 
>> gets blown up by a forgetful mind like mine...
>>
>> - Mike  KC4TOS
>>
>> On 3/23/2020 12:43 PM, Craig via ARC5 wrote:
>>>
>>> Thanks Mike and Robert. One can always hope on finding apparent 
>>> unicorns.......So for now, I think I'll start figuring out if I want 
>>> to play with analog or digital meters to create my own units, 
>>> although, when the weather around here clears up and we can kill off 
>>> the algae and mold in the yard, there are lots of things outside 
>>> that have a bit higher priority. 
>>
>
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-- 
Michael Hanz - KC4TOS

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