direct short #ubitx40help


KG5YUO
 

I have a version 5 ubitx. When I key the Mike I don't get any rd out but it pulls down my power supply to around 6.5 volts. I don't know where to start looking. The transmit relay makes then it pulls down the PS.

Thanks Bruce
"A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort."


Evan Hand
 

First, verify the obvious: That the 12vdc supply can provide the greater than 2 but less than 3 amps needed to power the transmitter. Use a current meter in series with the supply to verify the current draw.

If the supply is capable (more than 3 amps when transmitting),  I would start by separating the Power Amp (PA-brown wire) supply from the main board supply (red wire).  If the supply still dips, then the finals are not likely part of the problem.  I would then check wiring of the PTT and key to make sure you are not shorting the supply there.

If the supply does not dip, then the PA circuit is the problem.  You will then need to go through checks using the schematic.

In all cases, make the transmissions as short as possible to try to keep from damaging components.

Verify the above and get back to the group with any findings.  We will need more information to provide more help.

73
Evan
AC9TU