Re: Yaesu FT-7 No Transmit
The collectors of the PA transistors are permanently powered whenever the set is turned on, so you should see very close to whatever the voltage of the power supply is, on the collectors all the time.
If you look at page 2 of the coloured schematics, just to the lower right of the 10w amp module, you will see VR2105, which adjusts the collector current of the PA transistors. This will have some effect on the collector voltages and output power.
Re the base voltage, again on page 2 in the 10w amp module schematic, you will see diodes D1302 and D1303. They are connected to the centre tap of the transformer feeding the bases of the PA transistors (along with the bias voltage supply) and ground, being forward biased, you will see a voltage of about 0.7 volts on each base.
A common problem with both FT-7 versions is that the various plug in modules can get tarnished connections and also move slightly causing connector alignment problems. It is a common trick to remove and re-seat these modules to cure these various problems. No Tx can be one of these problems.
Do not be tempted to wipe fresh solder over these connections either, but rather clean them with either a glass fibre brush or old fashioned ink rubber or similar (be careful, as these things get older, the pads have a tendency to lift if treated too roughly).
If you haven't already done so, check the Tx/Rx relay contacts.
Last edited by Terry_VK5TM; 24th May 2019 at 1:47 am.
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