Thursday, October 14, 2021

Slowing a Muffin Fan...


I was helping a friend to slow the speed of his 115vac muffin fan on an amp, and felt it worth sharing here.

A capacitive divider doesn't dissipate heat like a resistor. Using a resistor takes about 1k ohm at 25w and it gets HOT.

The motors in these little muffin fans are an inductive brushless shaded pole design, and the capacitor will take advantage of that as a divider due to reactance at 60hz.

I've used 1uF @ 200vdc, polarity doesn't matter. A non-polarized cap would technically be best, but I have _NEVER_ had a problem using regular polarized caps. It runs cool as a cucumber. As you increase the capacitance, the fan will speed up. You can add a relay to an amp to bypass the cap when transmitting and bring the fan to full speed while keyed, if you want.

This is a cheap and simple way to lower AC voltage on simple motors and other fully isolated loads.

Dave WB4IUY

http://www.WB4IUY.net

Saturday, October 2, 2021

Hallicrafters SX-111 Faceplate...

I'm about to refinish the faceplate of a Hallicrafters SX-111 I'm restoring. I was hoping to retain as much of the original petina as possible, but there's way too much rust to allow me to sleep at night :-) This radio sat in a damp place many years. The electrical restoration wasn't difficult, but I want it to look good as well. I was able to locate the last 3 packs of Datamark white lettering in the new company owner's warehouse, so I'm sanding it down and starting over. 

Along with white, 1/8" tall lettering, there's a 1/16" wide white pinstripe all the way around the faceplate. I have a custom pin striping person that used to do work on my custom motorcycles, I'm going to try and talk him into that for me :-) Here's pics of the horrible face condition, just before sanding, filling, and priming work starts...









Dave WB4IUY 

Wb4iuy.net

Friday, October 1, 2021

Portable Shortwave Antenna...

 


I stumbled upon this in a batch of goodies I just got. Had not seen one in years. Even has the little antenna coupler still attached and working :-)



This neat little antenna will be handy when travelling, vacation, overnight fishing trips, etc. Stretch it out, slip the coupler over the collapsed antenna, and you're in business! Someone mentioned something similar is available from C-Crane.


Dave WB4IUY

WB4IUY.net

Monday, September 20, 2021

Cleaning Vacuum Tube Pins and Sockets

This is a short video explaining how I clean tube pins and sockets. While restoring and/or repairing tube rigs, I've found dirty/bent tube pins and sockets to be one of the leading causes of receiver noise and intermittant operations. 

 Dave WB4IUY

http://www.WB4IUY.net

 

Sunday, September 19, 2021

Repairing a Hallicrafters SX-111 Knob

 There was a piece broken out of the edge of the knob. Considering the age of this radio from the early 60's, I decided to try to repair it.
 
I made a little form to follow along the inner curve of the knob with tape. A small bit of 5-minute epoxy was built up in this area and allowed to harden over night.
 
I removed the tape, and sanded the outer curve and edge of the knob to match. Using a Dremel tool with a cut-off disc and a jewelers file, I replicated the grooves in the outer surface. After cleaning, it's now ready for a little touch up color to match, once I get that mixed.
 

  

Dave WB4IUY

http://www.WB4IUY.net