Fixing The Transciever

I've started repairing the rig, and have made some progress.

It turns out it wasn't completely DOA - cranking the volume to full brought a slight hiss in the headphones, and the relay clicked when turning it on. The tuning knob, however didn't change anything.

I started with the basic alignment steps, and set the AGC voltage OK. The next step, setting the VFO range by tweaknig L1, got me stuck. There was no signal coming out of Q3.

I then took the enclosure apart (remove four screws and the sides come off) and pulled various jacks and connectors so I could get to the board. When I turned it over, it wasn't a pretty sight. There was too much solder on the board, big globs on some connections, and lots of ugly residue. I guess when you pick up a kit rig cheap at a hamfest and the seller says "it just needs alignment" that really means "I couldn't get it to work".

I spent over an hour with a 10x magnifier peering at every trace, and fixed a solder bridge in the VFO circuit plus re-soldered a bunch of ugly places. There were definitely a few cold solder joints, which stand out as not having a nice, clean cone of shiny solder. A cold joint looks more like a blob and hasn't flowed onto the component wire or circuit trace well.

I also removed a bunch of the excess flux with alcohol. I'm not sure if this makes a difference to the circuit, but it makes it a lot better looking and easier to tell if there's a bridge or not between traces.

After the resoldering, things are lookng better. I'm getting close to the right frequency range out of the VFO, but am now hearing a constant tone in the headphones, so either it's kicked into transmit or something's oscillating.

6/20/2003

Well, something's messed up. I must have fried something in the power circuit because I'm blowing fuses on my little supply. I have an order into Mouser for a bunch of various parts (I figured out there's a bad diode in the keying circuit) so when they arrive and I get a better workbench set up, I'll dive back into this.

I'll update this when I make any more progress...

7/8/2003

I spent a few evenings resoldering most of the components on the board after realizing how spindly they were with long leads. Check out some of the photos before they were fixed.

The VFO circuit is still a bit flaky, but I'm not sure I trust my frequency counter. The BFO also seems to be way off, as I'm measuing 7+ mhz on the signal rather than the 11.999 I'm supposed to. I'll have to get my oscilliscope out and see if that makes anything clear.

In the meantime, I fixed the keying circuit. The 2N2222A transistor was replaced, and that gave me some reasonable voltages on the relay. The second diode (D11) on that emitter was also replaced, and now the key actually makes the relay click like it's supposed to. I found those components through a lot of trial and error, measuring voltages, resistance across diodes (with the power off !) and looking at the circuit to try and figure out what should be going up and down when the key is pressed. I also replaced Q10 and D9 in the process, but those seemed to be OK.