Smoked my SW40+ QRP rig

I’ll blame it on the recent time change. Actually, it’s somewhat related. Backpacking season is coming up and I’m already in the mood. On my list of things to do was get my portable station ready for a walk in the woods. My portable station this year will be my SW40+ QRP rig. I built this rig in May of 2003 but haven’t really used it much. It was built to exist in the Novice CW portion of the 40 meter band. Even though my code ability is more inline with the novice allocation I’ve decided to change the radio to the general CW subband. I’ll be carrying the radio more in the wilderness and would prefer to have extra activity that’s there in case I need to get an emergency message out.

Anyway, like I said I was changing the radio over to the general 40m segment. I pulled the thing apart rewound a torroid and pulled out the previous calibration capacitor (c7). I calculated the correct value of capacitor; 20pf. With it in place my Service Monitor found my carrier at 7.0247Mhz. That’s about where I was hoping to hit. Just a hair under 7.025. Tuning range goes up (birdie free) to about 7.060 so I’m really happy.

I went about hooking the thing up for fine tuning, I wasn’t sure how far off the tuning would be on this thing having dropped it that far. Things were going great, emphasis on “were.” Again, I blame it mostly on the recent time change and the misplaced hour of sleep last night. There were several other factors though, your typical chain of events type thing. I normally run the thing off a SLA battery but it wasn’t charged so I was using a 12v wallwart for most of the night. When I turned up the volume on the Service Monitor to listen as I was working to set the output power (between 1.5 and 2w) I noticed that I was getting AC into my tone so I quickly moved over to my primary station supply. My mistake at this point was not checking the voltage setting on this workhorse supply (it was set to a bit over 15v).

So I went back to setting output power. Mistake number 2 was paying more attention to sound of the signal than output power and accidentally turning the power adjustment two high. Pop.

I was a more than a little annoyed as the pop happened and I instantly knew fate. One component flamed for a few seconds giving of the required smoke. I figured the damage was catastrophic but refrained from throwing the thing across the room.

After the obligatory “why’d ya do that?” from my the wife (kd7vky) and some time to calm down I began a damage survey. Knowing where the flame came from it didn’t take long to find a blown diode. I checked a bunch of other components visually and electrically that would be suspect in such a situation. But to my pleasure, it was only one diode. I’ve got tons of diodes in the drawer… But after an hour of searching… no, I don’t have THAT diode or anything even close.

Annoying, it’s a ten cent part with $4 shipping from Mouser. Ofcouse I ordered extra, a few other suspect parts just incase there was other damage unseen and used it as an excuse to order a few other things to at least spend more than the shipping costs.

So it’s Ben Franklin’s fault, I’m sure of it, after all he’s the reason I lost an hour of sleep last night. Hmm, at least that’s the story I’m sticking to. 😉

This entry was posted in Ham Radio.