Elecraft XV Bypass Capacitor Change User Manual

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Elecraft XV Transverter Builder’s Alert

Bypass Capacitor Change

Revision B, April 30, 2009

We recently discovered that the XV50, 144, 222 and 432 transverters may experience erratic behavior under
certain conditions. There are two causes: RF energy entering voltage regulator U4, and voltage surges on the 5V
bus caused by the relay coils.

Even if you have not experienced any erratic behavior of your transverter, we strongly advise you make these
modifications to ensure stable operation under all conditions. They involve adding three leaded parts. You need
only remove the top cover.

You will need the following parts available from Elecraft. If you received this Builder’s Alert with your
transverter kit, the parts are included in your kit along with instructions about when to install them. See the errata
sheet supplied with your Assembly manual.

Quantity

Description

Elecraft Part Number

Capacitor, monolithic, 0.1 uF (104),50V,20%,0.1” lead spacing

E530020

Capacitor, electrolytic, 10 uF,16V,20%, 0.1” lead spacing

E530142

Procedure

Disconnect power from your transverter, remove the top cover four corner screws and remove the

cover.

Observe ESD precautions when inside your transverter. Wear an ESD wrist strap or

frequently touch an unpainted metal ground while working.

Locate voltage regulator U4. It is just behind the front panel with a heat sink tab bolted to the pc

board.

Install the two 0.1 µF (104) capacitors between U4’s center and outer pins as shown below. Solder

the capacitors directly the U4’s pins with very short leads. Hint: Bend the capacitor leads and hold them
with your pliers while tacking one lead onto U4 with your soldering iron carrying a small drop of solder.
Then solder the other lead, clean up the first connection if needed, and trim off the excess leads.

Check the resistance between the center pin and each outside pin using your DMM. It must be greater

than 500 ohms to confirm no shorts between U4’s pins.

(OVER)