[MRCA] MRCA Digest, Vol 216, Issue 6

[Jack Sullivan]

 WTB: AN/URC-104 with matching AC >PS or equivalent in good working order.
JackW2INF
    On Monday, April 4, 2022, 09:10:12 AM EDT, <mrca-request at mailman.qth.net> wrote:  
 
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Today's Topics:

  1. Re: ART-13 Junque Box Power Supply (Ray Fantini)


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Message: 1
Date: Mon, 4 Apr 2022 13:08:33 +0000
From: Ray Fantini <RAFANTINI at salisbury.edu>
To: "B. Smith" <smithab11 at comcast.net>, Military Radio Collectors
    Association    <mrca at mailman.qth.net>
Subject: Re: [MRCA] ART-13 Junque Box Power Supply
Message-ID:
    <DM8P220MB0472B177400A7C1768DD8C3DB8E59 at DM8P220MB0472.NAMP220.PROD.OUTLOOK.COM>
    
Content-Type: text/plain; charset="utf-8"

It was a common practice in a lot of the last generation of Harris Broadcast tube transmitters to install the plate current meter in the negative side of the plate supply. They would install a ten or fifteen volt Zener Diode across the shunt so if the resistor opened the diode would short and protect the plate current meter. After a bad lightning strike it was not uncommon to find the transmitter on the air, putting out full power with no issue but the plate current meter reading zero.

Ray F/KA3EKH

From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On Behalf Of B. Smith
Sent: Sunday, April 3, 2022 7:40 PM
To: Military Radio Collectors Association <mrca at mailman.qth.net>
Subject: [MRCA] ART-13 Junque Box Power Supply

CAUTION: This email originated from outside of Salisbury University. Please exercise caution when clicking links or opening attachments from external sources.

The ART-13 plate current meter circuit requires a meter "shunt" to be installed in your power supply and the voltage taken from this shunt is used to drive the  meter.  Usual this is a resistor around 12 to 15 ohms.
When constructing this "shunt" try using two or more  resistors in parallel and avoid just using a single resistor. By using a pair of resistors if one fails you will still have a DC return to chassis ground and your meter in this case will not be accurate but the power supply will be safe and still function. BTW the meter scale is not very accurate anyway in the plate current function. Full scale is around 300 ma.
Z
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End of MRCA Digest, Vol 216, Issue 6
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