Tuesday, September 29, 2009

Citation I Refurb - Repairing Terminal Board A

If you recall from a previous entry I discovered two terminal lugs on Board A were broken, snapped at the base.  These were lugs #62 and #69.  My first attempt to fix this was aimed at trying to preserve the original look of the board by reattaching the broken lugs.

I was reasonably successful in reattaching the broken lugs to the terminal board.  This was accomplished by using a length of bare #22 gauge wire.  I crimped one end of the wire back onto itself a couple of times.  This formed a small "ball".  The wire was passed up through the bottom of the terminal board.  If the ball is large enough you cannot pull the wire all the way through as the ball stops it at the terminal board.  The wire is then threaded through the terminal lug and out the top hole of the lug.  The lug is seated tightly against the terminal board and the wire extending out the top of the lug is bent tightly over the top and clipped off, leaving a couple of millimeters to anchor the lug.  Solder is then run into the lug from both the top and bottom.

This results in a very good looking repair.  When finished the lug looks original and it feels rock solid.  So I fixed both lugs this way and proceeded with the assembly of the terminal board.  As you may guess by now, this repair may look sound but it doesn't really work well.  As soon as you solder components to the lug, the solder inside the lug melts and the lug comes loose from the terminal board again.  You can get around this problem by simply holding the lug firmly in place with a needle-nose pliers after soldering the components to the lug.  Heat up the lug to melt the solder while holding the lug in place with the pliers.  Keep the lug firmly in place while it cools and the solder solidifies.  This works, but it just doesn't seem like a quality repair to me.

So on to option #2.  A search of the internet parts stores turned up a store called Angela Instruments.  This place seems to specialize in parts for the repair of vintage guitar amplifiers like Fender, etc.  They had kits to assemble entire turret boards.  Well, I didn't need a whole turret board, just a couple of lugs.  But this opened the door to a better search of the internet now that I knew what I was looking for.

I found what I was looking for from a company called Keystone Electronics Corp (http://www.keyelco.com/).  They sell a variety of terminal lugs and the necessary tools to mount them to boards.  The lugs that came closest to what I was looking for were 0.172 double turrets.  The exact variation to mount in the Citation board was Part #1503-4.  In order to mount these in the board I needed what is called a staking kit.  I didn't want to invest a lot here for what would be used for a couple of turrets.  I found what I needed in Staking Tool Part#TL-8.  This consists of a small anvil and a top setting tool (or swager).  I ordered these parts from Mouser.  The staking kit was $17.25 and the termial lugs were $0.41 per lug.

The parts are shown in the following photo.



Before you can install the new lugs you need to remove the vestigial traces of the old lugs.  The lugs were broken off at the top of the terminal board leaving a metal portion of the lug embedded in the board.  This must be removed first.  I use a combination of Dremel tool with a filing bit and a regular power drill with a regular drill bit.  You have to proceed very carefully when removing the lug traces.  Do not simply apply a power drill and bit to the socket and press the power button.  Through a process of slow and deliberate work the remaining lug stub can be extracted.

The bottom of the lug (the mounting portion) is inserted through the hole in the terminal board from the top.  Just a tiny length extends out the bottom side of the board.  The small part on the left is the anvil.  The anvil is placed on a solid surface with the large hole facing up.  A table vise works well.  You want a hard surface.  You will dent any soft surface that you try this on.  The top of the lug (mounted through the terminal board) is inserted into the anvil hole.  The bottom of the lug is pointed upwards and you will be looking at the bottom of the terminal board now.  You now use the swager, the longer tool on the left, to set the turret.  If you look at the left end of the tool you will see the setting surface.  You simply put this end of the tool into the end of the terminal lug and you use a hammer to strike a few blows to the swager.  The force of the hammer and the geometry of the setting tool surface will spread the bottom of the lug, mounting it in the hole much like a rivet.  Give it enough hits with the hammer until you have what you feel is a nice tight fit.




Above is the picture of the finished work.  Not exactly stock, but very solid and usable.

Total Time Spent:  ~1 hour.

No comments:

Post a Comment

Post a Comment