Category Archives: Repairs

Holy Hanna!

20151121_072647February is half over and I haven’t posted at all this year so far!

In truth, I haven’t done squat so far this year with regard to radio stuff. Well almost nothing, I have made it to three VE sessing so far this year. The next one is this Saturday.

I really wish I had more to report but I basically had to shut down all of my radio projects because I just don’t have the time right now.

One radio related project I can report is a partial disassembly of the Hillbilly Radio Tower. I pulled the 70 cm and 40 m antennas down leaving only the 2 m antenna in place.

The 70 cm was working fine, I just don’t use it that often and I needed to pull the 40 m down anyway, so I opted to clean up the cabling on the back porch.

The 40 m had to come down, or be adjusted. It was tilted from the high winds of the last storm that blew through. It was still useable, just leaning about 30 degrees off vertical. After cleaning up the mast the 2 m is hardly noticeable, which is a good thing.

Other than the antennas, nothing going on or planned for the near future. I will make an attempt to get back before another 2 months goes by.


New-To-Me Signal Generator

120 kc (kHz) to 200 mc (MHz)
120 kc (kHz) to 200 mc (MHz)

On Saturday I picked up a few things at the De Anza Electronics Flea Market. The most impressive acquisition would be the Lafayette Signal Generator for $20.

I have been needing one and I was dreading the prospect of having to build one and having a tough time without the right tools for calibrating it, so this was a great find and a steal of a value, though I didn’t know it for sure until today.

One thing I have learned about buying used electrical/electronic equipment, particularly in at a flea market, is that you have to take your time and open it up, get documentation, inspect and clean the equipment before attempting to use it, or plug it in for that matter.

20150414_075130 Sunday was opening day. I noticed right away that I would need to replace the power cord grommet as it was in two pieces. I didn’t actually get to anything else until today.

Today I inspected all of the wiring and components, looked for hot spots and anything that would indicate an over heat. Having found nothing of the sort I moved on to cleaning, which there was surprisingly little to do. I made sure the tubes were cleaned and had no fingerprints on them. Now that I have a piece of tube equipment I will need to get a tube tester. ๐Ÿ˜‰

With the cleaning done it was time for the plug-in and smoke tests. No pops and and no smoke! I let everything warm up and burn in for a good twenty minutes before starting any tests.

Testing with the oscilloscope began with the AF (audio frequency) side of the generator. After the twenty minute warm up period the “approximately 400 cycles” audio tone as specified in the manual turned out to be stable at 388 cycles (Hertz). I can work with that.

“kc” is kilocycles. The term is essentially the same as the more familiar kilohertz along with “mc” megacycles being the same as megahertz. The change over in terminology occurred slowly from the mid 70s to the mid 80s. Many hams still use kc and mc. I use them interchangeably depending what I am referencing or who I’m talking with. This piece of equipment has frequency labeled on the dial as kc and mc.

20150417_152319Moving on… The generator did its first diagnostics job with a portable amplifier I have had for a very long time (the one on the right). I clipped on the amp to the audio out and it turn out the volume control on the amp is trashed from banging around in my tool bags for a couple of decades so I will need to replace the potentiometer in that this weekend.

I then moved over to the RF (radio frequency) side of the generator and clipped on the oscilloscope. The RF side is divided into 5 switchable bands. I checked each band by referencing the frequency on the dial with the frequency on the O-scope. All five bands checked out very closely to the dial. A little lead or lag here-and-there, but overall pretty close for this equipment and its age which I’m guessing is about as old as me (made in the mid/late 60s).

20150417_152206The frequency counter I purchased last year has been giving me problems. New equipment, cheap (figuratively and cost), and no manual. With the help of the new sig gen and the oscilloscope I managed to fix a couple of minor problems and figure out the modes on the counter in the process. Looks like the electronics bench is finally coming together.

Now that I can check the receivers I build I can also check the transmitters I plan on building. I can also check portions of the radios as the construction moves forward. I plan on building more of my own test equipment but it’s nice to have a reference point or two to calibrate off of.

I also did some diagnostics on the 40 meter direct conversion receiver project and updated the project page… some very interesting results, you should take a look. ๐Ÿ™‚

A productive day I think.


Boafeng Hand Mic Repair

Magic Smoke?

20150228_105506I was out picking up some components from Jameco for theย 40 meter receiver I am working on. It was in the morning so I figured it would be a good time to tune in to the 9AM Talk Net.

After calling in my call-sign and waiting until net control called me up wouldn’t you know it, something went wrong. I keyed the mic but nothing happened. No Tx at all, not just not being heard, but the radio showed no sign that the PTT key was pressed, nothing. Looking back it seems obvious, but at the time I wasn’t sure what the problem was so I unplugged the mic and continued without it.

A couple of days later I opened up the mic fully prepared to do what ever needed to be done to get that puppy back in service. I set aside time, cleared the bench, gathered my tools and a multimeter, laid out a mat, took a deep breath, and opened the mic case.

Wouldn’t you know, the PTT wire broke loose from the solder joint. I spotted it as soon as I opened the case. 3 minutes and a hot iron and all is well.

One quick repair down and one satisfied customer, me.