TT 1340 transceiver: stuck about an inch from the finish line....

[KC2SIZ]

The rig is almost complete, but I'm not getting any output power. When I key the rig there is a clear sidetone, and in all other respects the rig appears to be fine. But there's currently no output and the needle on my wattmeter isn't budging. Since I'm about out of ideas and expertise, I thought I'd see if anyone here has an insight to share.

I tested for continuity across the metal heat sink on the back of the PA (Q15) and the aluminum heat sink it’s attached to. There’s no continuity there, so I don’t think a short affecting the PA is the issue. I also checked out the PA itself with my DMM and it appears to be fine.

I was very careful when winding and installing the toroids T1 and L8-L10 and have rechecked them. They each have the correct number of windings. The windings of L8-L10 are also compressed at the top of the toroids, as suggested in the Ten Tec manual.

When I’ve tested the rig for output power, I’ve used both a 50 ohm dummy load and a 40m antenna. Results were the same in each case…no output power.

And that's about it. Thanks for reading.

[AB9LZ]

Assuming you don't have an O-scope... now is the time to make a simple RF probe for your DMM and start tracing the signal from the VFO. It's likely that you have a cold solder joint somewhere.

Signal tracing and debugging can be a fun experience, for me it's the best part of building stuff.

73 m/4

[KC2SIZ]

Excellent suggestion. I'm on it! Thank you.

[KC0YEJ]

Misread... please disregard.

Brian

[KC2SIZ]

I have an RF probe now and am hoping someone can tell me what readings would be normal at various points between the transmit oscillator and the PA?

[KE3WD]

When troubleshooting, precise voltages are not needed.

Look for signs of life, any RF at all.

Logical order, start at the antenna jack and work your way backwards through the stages looking for that point where you suddenly encounter RF voltage. There may be a situation where you read a wee little bit at the antenna, but keep going backwards, looking for some point where there is more sig than that wee little bit.

As you work backwards through the stages, expect the signal in a healthy rig to diminish appropriately, since you are basically going backwards through gain stages as well.

Also a good idea to check the DC status of each bipolar transistor that is supposed to be in the "turned on" state when transmitting. This is easy and a rule that applies to ALL bipolar (NPN or PNP) silicon transistors. If the transistor healthy and DC bias resistances and current paths are correct, you should read about 0.6 to 0.7VDC from Base to Emitter of the transistor. This method can often pinpoint problems with the device itself, such as shorts or leaks, as well as its surrounding resistances being right and in the right place. Can even spot a shorted capacitor in such circuits, or an electrolytic that may be installed backwards as well.


73

[KF6KXG]

Check that you sanded the ends of the toroid wires down to bright copper to get a good contact with the board. This is a common problem on kits that use toroids. 73 Mike KF6KXG