OK
I am u and running now
The schematic on line is different to the version I have for the input stage on the RF power amp.
The long IPX jumper feeds the modulated RF signal to the board. Its pretty low level. Maybe 50mW. You can see a test point next to the jack you can connect a CRO up to.
I disconnected that and fed a 7.023MHz signal ftom a Pixie QRP transeiver into the power amp and discovered the first transistor Q5B on the input was not working. If I fed the signal to the collector of the transistor, I got more output.
Measured the device with a meter in circuit and didn't get the usual diode readings from B to C or B to E. I carefully removed it with a tweezer iron I have for this work, and tested it out of circuit. Base was open.. So I cleaned up the pads and soldered a 2SC8050 in its place. That got it working with full fignal.
After attatching the jumper, the device seemed to work OK, however, I carelessly hit the top of the antenna switch relay which made a bit of a mess so it wouldn't switch. I clipped off the melted plastic top and its OK now. I will repalce it one day
Here are some photos.
I put fiber washers on the transistors as the screws into the heatsink protruded past the base of the heatsink plate underneath the board. Now th eteatsink is plat and makes a solid contact with the case itself
To troubleshoot yours, disconnect the screen and top board.
Remove the tinned covers from the amp baord as I have done
Check all of your transistors / fets in circuit for obvious short circuits
If you dont find any...you'll need to test on a live board.
Hook up the ribbon cable between the boards. Don't worry about the coax jumpers
Hook up the front pannel / screen baord and carefully rest it so you can operate it, without shorting anything out
Connect up a power meter and dummy load.
Connect up a CW key or a switch to the Key jack
Connect up power
Set the radio to CW
Set the keyer to manual
Tune your radio to the frequency of your signal generator which you set to the frequency you want to test
Now
Feed a signal into P4B - You can hook up a piece of Cat5E solid cable and use that as a pin into one of the coax jumpers, and plug the other end into P4B. Ground anywhere convenient.
Close the CW Key.
Check the bass and collector signals on Q5B. You should see amplification. If not. That's what I had.
Follow the signal through the stages and make sure your'e seeing a bigger signal on the output of each stage.
With the blown transistor, I was getting 7W with around 2V of drive. Once I changed the transistor out, I pegged the 20W meter for the second I gave it 100mW. Everything worked.
I could not have fixed it without a CRO or an RF signal source. Having a really good soldering setup made life much easier, as well as a jewelers magnifying visor.
The original chip transistor is available from Mouser though I am not what gain rating it has
Hope this helps
