"Don and Diana Cunningham" <[EMAIL PROTECTED]> made an utterence to the drakelist gang
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Thanks for that tip, Carel! I'll check my two and see what I find now.
Vy 73,
Don, WB5HAK
----- Original Message ----- From: "Carel, PA0CMU" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, November 26, 2004 5:03 PM
Subject: Re: [drakelist] TR7 mode switch thump. PROBLEM FOUND
"Carel, PA0CMU" <[EMAIL PROTECTED]> made an utterence to the drakelist gang
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Hi all,
The problem of the mode switch thump has been found.
On the early version of the 2nd IF/Audio Board, R1187 doesn't exist. On the late version board Drake added R1187 (10K) in series with CR1119 but made a mistake in the copper trace design. In some (or most ?) cases, R1187 is short-circuited! Switching to CW mode still charges C1151 (22uF/16V) immediately through CR1119, thus giving a loud click in the audio circuit.
I added a 10k resistor to my early version board and Rien - PA0TRT, modified the copper trace of his late version board. Both TR7's (S/N 3157 and 9345) are switching without any click to CW mode now.
73, Carel - PA0CMU.
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