Removal and Replacement of Stud-Type Diodes

TM 11-6625-467-34

removed from the board and replaced with another

polyethylene container and stir with a stainless

part, the following procedure should be followed.

steel spatula or equivalent. Mix thoroughly.

The bonding agent used in recoating the boards is a

i. Apply the mixture to the newly soldered joint;

postcoating material, Dennis 1169. This material

c o v e r all areas where the original coating was

consists of two parts, Dennis 1169A and 1169B. The

damaged and any new parts which were added. Use

two parts must be mixed at the time of use.

a soft-bristled brush to apply the mixture.

a. I n s p e c t t h e c a r d f o r e v i d e n c e o f b u r n s ,

j. Allow the newly coated cards to dry to a

scorches, or heat damage; corroded metal parts or

tackfree condition (approx. 2 hours) before install-

terminals, or damage of the base laminate. If any of

ing them in the equipment. The final cure takes ap-

these defects are evident, replace the entire board

proximately 7 days at room temperature or 1 hour

rather than attempting repair. If the board appears

at +60 C. (+140F.); however, the equipment may

repairable, proceed to b below.

be operated during the curing period.

b. Remove the designated part from the card by

3-11. Removal and Replacement of

destroying the protective postcoating with a hot

Stud-Type Diodes

soldering iron, and then unsolder the part and lift it

(fig. 3-26)

off the board with a pair of long-nosed pliers.

The stud-type diodes in the test set must be elec-

CAUTION

trically insulated from the chassis to which they are

Do not use soldering irons rated above 25

mounted. Follow the procedures in a and b b e l o w

watts on cards bearing transistors, cerafil

when removing or replacing this type diode.

capacitors, or other heat sensitive com-

a. Removal.

ponents. Also, be very careful when re-

(1) Unsolder the wire or wires connected to the

moving components from the card so that

anode lead of the diode.

the circuits are not damaged.

(2) Remove the nut from the bottom of the

c. If necessary, remove the excess solder from

chassis.

the joint with a soldering iron.

d. Insert the new wire or component lead in the

correct eyelet and clinch the wire over the eyelet.

e. Apply solder to the joint using any rosin flux

core solder. Do not use a solder that has a core of

hydrazine, acid, or other unapproved flux. Do not

keep the iron on the joint longer than necessary to

complete the solder flow throughout the joint.

f. Inspect the solder joint to be sure the solder

completely covers the joint and there is a smooth

continuous band of solder between the eyelet flares

and the circuitry. Note also that there are no cold or

fractured solder joints or nonadherence of solder to

metal and no excess solder globules, peaks, strings,

o r bridges of solder between adjacent parts or

circuits.

g . Clean the joint to remove the flux; use a

m e d i u m - b r i s t l e d brush and a small amount of

organic solvent. Remove as much of the melted plas-

tic and flux from the soldered area as possible.

Remove excess solvent and dissolved flux with an

absorbent material.

NOTE

Use a solvent sparingly since the

postcoating will also be dissolved. Apply a

small amount to the area of the solder joint

only.

h. Mix one part of Dennis 1169A liquid with one

part Dennis 1169B liquid. Mix these two liquids

together in a stainless steel, wax free paper, or

Figure 9-26. Insulated mounting of stud-type diodes.

3-39