6300 and the ARB-704 buffer

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  • Updated 3 years ago
Hello,

 Is anymore specifically using the ARB-704 buffer with their 6300 in keying their amp, I would like to know how to connect this to my 6300 to be used with my SB-220 amp.

Thx.

Peter/ve3pcd
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Peter

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Posted 3 years ago

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Bill Roberts

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I purchased that buffer box to protect my Flex 5000 and then moved it to the 6300.  Not sure it's necessary with an ALS 600 but IMHO, it's good insurance.
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Peter

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"I purchased that buffer box to protect my Flex 5000 and then moved it to the 6300."

How did you connect it to your 6300 ?
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Paul Christensen, W9AC, Elmer

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Peter,

Based on the ARB-704 manual, it would be connected as follows:

1) ARB-704 TX-SEND jumpers set for LOW SYSTEM;

2) ARB-704 J2 (Radio) connects to the Flex 6300 TX KEY line;

3) ARB-704 J1 (AMP) line connects to SB-220's key line.

Unless your SB-220 has a Soft-Key modification, you definitely need this or other amp buffering device.  The Flex TX RELAY key line is rated at +40V/140mA.   An unmodified SB-220 key line is more than +120V.  The ARB-704 would not be my first choice, but you've already got it on-hand.

Paul, W9AC 

(Edited)
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Peter

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Hi Paul,

 My Sb-220 amp has all of the mods including the soft-key.

Peter
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Paul Christensen, W9AC, Elmer

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You should still use the ARB-704 even if the SB-220 has the Harbach Soft-Key mod.  Here's why:

If the Soft-Key's Q1 fails with an open base, +120V from the amplifier appears back at the Flex's amp key line.  Since the Flex TX Relay line is only rated for +40V, the +120V key line from the amp will damage the Flex TX Relay output circuit. 

Without the ARB-704, one solution is the inclusion of a +2.5V Zener diode at the junction of the Soft-Key's R1 and Q1 (base).  The added Zener is current-limited through R1 and will clamp the transceiver's key line to no more than +2.5V during a fault condition.

Paul, W9AC

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Peter

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Thanks so much Paul, much appreciated OM.

73
Peter/ve3pcd