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Re: How Does Voltage Get to the Finals? #QMXplus

 

Steve, the power to the finals goes through Q507 to L502 and then to the center tap of the primary of T501. The two ends of the primary winding of T501 then go to the drains of the finals. Look at the schematic to follow it per the above. The schematic label is "+12v" but that implies?+9v if that's the supply you are using. There will be some voltage drop along the way, but the voltage at the finals will be a little less than whatever the input voltage is set to.? Also, the DC voltage you measure at the drains of the finals will be affected by the RF at those points. You would be better measuring that at the T501 center tap or at the drain of Q507. In the photo it appears you are getting 6.0 watts output, so I don't think you have a problem.

The warnings?about over voltage apply to both voltage levels used.?

73 .. .Ron

On Sat, Dec 7, 2024 at 11:59?AM Steven, W2MY via <stevenpituch=[email protected]> wrote:
One thing that I haven't figured out yet is how the power gets to the finals. I don't understand how a 12 Volt supply is equivalent inside the radio to a 9 Volt supply.? Yes there is a transformer that is wound differently for either type of supply.? But is the voltage delivered to the finals the same whether the supply is 12 V or 9 V?
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The reason I am asking this is that I choose a 9V supply.? I use a 4 cell lithium ion pack (16.8 V) and I have a voltage regulator to bring this down to 9.00 Volts.? When I go into the Putty diagnostics, the voltage at the finals is always shown as 7.5 Volts, regardless of the band.? I checked and the voltage supply stays a constant 9 Volts during key down.
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So my questions are:?
1)? Is the voltage to the finals the same regardless of the voltage (9 oe 12) chosen for the power supply?? ?
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2) Why are there so many warnings about not going above 12 Volts (I assume for the 12 Volt supply), but no warnings about going over 9 Volts for the 9 Volt supply?
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3) Is everyone else getting 7.5 Volts to their finals regardless of input supply voltage, or do I have a problem?
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Thanks for all the help.
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Steve, W2MY
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