Current Project
SWAN 350 and National Speaker Emblem Repoduction
The Swan 350 had several problems initially. 1: intermittent audio on receive 2: no output on transmit
The first problem turned out to be corroded connections in the jones plug. Cleaned each pin an problem went away.
Now on the the transmit problem. Every thing appeared to be working, just no output. After transmitting for 20 seconds I noticed the driver
glowing brightly. After further inspection it was found that the rf choke to the diver was open, thus no b+. Fortunately
the rf choke had burned open on the outer layer and was easily repaired. Now I had some grid drive on transmit with about 30 watts output,
not to good for a 400+ watt pep rig. I suppected bad finals, 6hf5 sweep tubes. Before I could get to them, during the grid tuning process I heard a pop
and no more rf. The grid cap had arced and popped the rf choke again. Now I know why the choke opened. Again I was lucky that it opened on the outer layer.
After looking at the schematic, the grid variable cap has 300 volts applied only on 80 and 40 meters. On the other bands there is a cap in series blocking the b+.
So instead of trying to work on the pitted varicap I placed a .002 cap in series. It work fine on all bands except 80, where the extra series capacitance
was causing a the grid circuit not to resonate. So I decided to pull the varicap and go to polishing. After a suggestion from Mike Lord K4ELV, I decide to try
my dremal tool with the small sanding disc. The disc is thin enough to fit between the plates with out a problem. I sanded the burrs and pitts, on some of the vanes it
took quite a bit of the aluminum away. If tuned circuit moves a little because of the mechcanical movement of the vanes, it should not cause a problem in this grid circuit. I reinstalled
and put the circuit back to it's original state. All seemed fine, except the low output. I then moved to replace the finals, I found a pair of nos 6hf5's on Ebay. After installing
neutralizing and aligning, I have 240 watt carrier and plenty of audio. I tuned up to 20 meters on my 80 metter dipole, I heard a I2 calling cq and answered him, got a 599.
Pretty good for first contact.
National Speaker Emblem Repoduction
I have 2 national speakers that were missing the emblem, this seems to be a common malady. I had been wanting to find something for a while to make a mold
and try a pour of a resin or such. I still haven't done that, but did find an interim solution. I used some modeling clay to make the mold. It's brand name is Sculpty, and can be found
at hobby stores , such as Micheals. This clay hardens after beening put in an oven for 10 minutes at 275 degrees F. I took a piece of the clay and made a mold by pressing against the emblem
on my NC300. After hardening the mold, I rolled out some clay to the thickness that I needed, pressed into the mold, removed and baked at 275 for 10 minutes. (note if you are using a toaster oven,
watch carefully, the heating element is close to the clay and will burn it quickly. My first 2 were toast.) My 2nd attempt was done in a conventional oven without any problems. I then picked out some paint
and the pictures are the result. I attached a bugel head screw to the back with rtv for mounting. Mounted in the speaker it is more than satisfactory.
