Friday, October 23, 2009

A Bold Fresh Method of Mounting the Display LEDs

OK, so I borrowed a bit of the title from Bill O'Reilly.  I think a bit of poetic license is allowed since I have a Grand-Daughter named after him.  (No they didn't name her Bill, her name is Reilly.)

If you've received a DRO-350 or DRO-350+ kit from Wildhorse Innovations lately, you may have noticed the scraps of plastic from the display LED windows (in the case) included in the kit.  This isn't just a way for us to get rid of some plastic scraps.  These scraps can be used as spacers to raise the display LEDs so that they are closer to the faceplate.

Above is a picture of one of these scraps.  Note the lines embossed into the plastic.  They will be mentioned later.

The first step in our process is to alter slightly the order in which the DRO-350 components are installed.  As you will see later, this is an optional step, but IMHO makes the job a bit easier.  The area outlined in red in the picture below shows the area where no components should be installed until after the display LEDs have been installed.  These components include Y1, DS15, D2, D4, D5, D6, D7, R1, R2, R28, C1, C2, JP2 and U1.  If you are building a board for a DPU-550 many of these components will be omitted from your kit already.  In the case of U1 (when building a board for a DPU-550), do not install the headers that will be positioned at U1 until the final assembly.

The following components may be installed prior to installing the display LEDs, however you may find it convenient to leave them out until after the LEDs are installed. D3, JP1, C7, R27 and Q1.

The following picture shows the relationship of the spacer material to the LED when the LED is mounted on the board.  Due to variations in manufacturing, the spacer may be slightly wider than the spacing between the LED legs.  In this case, brief sanding to narrow the spacer will solve the problem.

The installation procedure is as follows:

Fill a single corner hole for each display LED mounting point with solder. The hole should be filled so that it domes slightly.  Having too little solder will make it more difficult to melt the solder in the following step.

It makes no difference with which row of LEDs you begin, but remember to begin with the LED that is closest to where the switches will be.  If you begin at the opposite end of the row of LEDs, you will have no easy way to remove the spacer after the final LED in the row is installed.  There should be three spacers included with each kit, so the spacer could remain in position under the LEDs if necessary.  I tend to be a bit of a "neat-nick" and prefer to have the spacers removed once the LEDs are installed.

Holding the spacer and the LED such that the spacer is between the board the the LED, engage as many of the remaining holes as possible.  While holding the spacer and the LED in this position, heat the solder in the corner hole.  As the solder becomes molten the LED should slip into position.  If it does not move into position easily, do not force it.  One of two things is occurring.  Either the solder is not yet molten, or the LED is not in the proper position.

BE SURE THAT THE LED IS PROPERLY ORIENTED!!!  I hate to admit that more than once I have soldered an LED into position, only to find that I have installed it upside down.

When the solder has become molten and the LED has slipped into place, carefully examine the relationship of the spacer, LED and board surface.  Be sure that the LED is level in all directions.  If adjustment is necessary, heat the solder just long enough to move the LED into position.

NOTE:  Raising the LEDs by this amount does not allow the legs of the LED to protrude completely through the PCB.  However, the end of the legs is typically at, or slightly below, the surface of the PCB.  Be sure to use sufficient solder that the solder wicks through the hole and "climbs" up the LED leg on the opposite side of the PCB.  In addition, there should be a slight "dome" on the side of the PCB from which you are soldering.

Now solder the leg if the LED that is diagonal from the leg just soldered.  Again examine the position of the LED and adjust as necessary. DO NOT solder any additional legs at this time.  By leaving the LED with only two legs soldered, further adjustments to position are easily made.


As mentioned at the beginning of this article, one side of the spacer has a pattern of lines embossed into it while the other side, though somewhat textured, is basically level.  When installing the LEDs, having the side with the embossed lines up, or in other words, against the bottom of the LED makes installation easier.  If the embossed side is positioned against the surface of the PCB, the lines will have a tendency to catch on the slightly raised surfaces surrounding the holes in the PCB.  While moving the spacer with the lines against the PCB is not impossible, it is my preference that any "abuse" that might occur, occur against the bottom of the LED as opposed to the surface of the PCB.

You are now ready to install the next LED.  Slide the spacer in the direction of the next LED position so that only a quarter inch or so remains under the LED just installed.  The next picture shows the position of the spacer as the final LED in a row is being installed.  Note the generous amount of scrap with which to grab in order to remove the scrap.  Depending upon how tightly you hold the LEDs as you solder the initial two corners, the spacer may have a bit of resistance to being removed.  This is especially true if you have the embossed lines on the scrap against the PCB.

After installing all of the LEDs, make one last detailed examination of the installation.  Are the LEDs properly oriented?  Are they level with each other and reasonably well positioned in relationship to each other?  Once you are satisfied that all is correct, solder the remaining pins on all the LEDs.

You are now ready to complete the assembly of your DRO processor board.

One last task.  When the display LEDs are positioned flush against the surface of the PCB (no spacer used in the installation), the five indicator LEDs should be positioned so that they extened about 1/8" above the face of the display LEDs.  With the display LEDs raised as in this procedure, that rule of thumb no longer applies.  Again we can use our scraps of plastic.  Referencing the following picture, place the scrap on the surface of the display LEDs.  The top of the indicator LEDs should extend above the surface of the display LEDs a distance equal to about 1/2 the thickness of the plastic scrap.

Well, as Porky Pig use to say "Th, th, th, that's all foks".  I hope this article has been helpful and results in better display viability for your ShumaTech DRO.  Feel free to offer comments or suggestions, and as always, thanks for visiting us here at Wildhorse Innovations.