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A fault in a bias circuit and in the circuit that is meant to switch the bias OFF in receive mode could do this. Good RF transistors will draw current on standby if there is a source of base current.

Simply lifting the base terminal of each transistor would tell you if this is the cause. A DC meter onto the pcb foil where the base was unsoldered would show if the keying circuit isn't turning off the operating bias. My first test is to probe the now-loose base lead of each transistor. Typical transistor failure will show voltage leaking from the collector voltage supply. A good transistor will show zero Volts DC on the loose base lead.

Quick and simple, I'll guess maybe the pcb foils for the RF transistors' base terminals are showing voltage in receive mode. This would cause perfectly-good transistors to draw current in receive mode.

73

<blockquote data-quote="nomadradio" data-source="post: 809854" data-attributes="member: 22">A fault in a bias circuit and in the circuit that is meant to switch the&nbsp; bias OFF in receive mode could do this. Good RF transistors will draw current on standby if there is a source of base current. Simply lifting the base terminal of each transistor would tell you if this is the cause. A DC meter onto the pcb foil where the base was unsoldered would show if the keying circuit isn&#039;t turning off the operating bias. My first test is to probe the now-loose base lead of each transistor. Typical transistor failure will show voltage leaking from the collector voltage supply. A good transistor will show zero Volts DC on the loose base lead. Quick and simple, I&#039;ll guess maybe the pcb foils for the RF transistors&#039; base terminals are showing voltage in receive mode. This would cause perfectly-good transistors to draw current in receive mode. 73</blockquote>

[QUOTE="nomadradio, post: 809854, member: 22"] A fault in a bias circuit and in the circuit that is meant to switch the bias OFF in receive mode could do this. Good RF transistors will draw current on standby if there is a source of base current. Simply lifting the base terminal of each transistor would tell you if this is the cause. A DC meter onto the pcb foil where the base was unsoldered would show if the keying circuit isn't turning off the operating bias. My first test is to probe the now-loose base lead of each transistor. Typical transistor failure will show voltage leaking from the collector voltage supply. A good transistor will show zero Volts DC on the loose base lead. Quick and simple, I'll guess maybe the pcb foils for the RF transistors' base terminals are showing voltage in receive mode. This would cause perfectly-good transistors to draw current in receive mode. 73 [/QUOTE]

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