Re: Ultimate3S additional power transistors Help!!!!!!!
Phil remove the the 5 volt jumper so that you can supply the PA with say 9to 12 volts. 5 volts is not enough for 3 x BS170. So in summary 5 volts to the U3S circuit and higher voltage to the PA. You will see the PA connection points right beside the 5 volt supply.
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-------- Original message --------
From: Phil Crockford <pcc@...>
Date: 2020-07-24 18:15 (GMT-04:00)
Subject: [QRPLabs] Ultimate3S additional power transistors Help!!!!!!!
What am I doing wrong? I have an Ultimate3S. I have recently built. It seems to work fine. I am using it in WSPR and CW.
It is running on the 10M Band and producing around 170 Mw of power on the band. All is fine. I wish to install two additional BS170 Power transistors as provided for on the board. The existing BS170 is powered from a separate 5Volt supply. The documentation states that I may get a small amount of an increase in the power output with the two extra transistor on the existing 5 volt power and the heat in the existing BS170 will be better dissipated in the additional transistors. However if I install the two additional transistors the power decreases to 100Mw at the output at 5 volts. I have changed the two transistor more than twice to ensure that I don’t have a faulty component but it is still the same. I have adjusted the bias with the 3 transistors installed.
Can anyone shed any light on what I am doing wrong?