Hafler DH-110 manual ALL Solder Used Must be Rosin Core

Excess solder may be removed from a connection by heat- ing it and allowing the solder to flow onto the iron, which is then wiped on the sponge.

ALL SOLDER USED MUST BE ROSIN CORE

Never use acid core solder or any separate flux in elec- tronic work. Silver solder is also not suitable. If in doubt about unmarked solder, always obtain a fresh supply of rosin core solder. We recommend 60/40 for easiest use. Do not confuse it with 40/60, which is harder to melt.

The general procedure is to use a hot iron for a short time to heat a connection, then add solder with the iron still in contact. Remove the solderonce it flows, and then remove the iron. A cooler iron applied for a longer time is more likely to damage components, or lift the copper circuit pat- tern from the boards. A break in the etched circuit can be mended by simply soldering a small piece of wire across it. Do not allow much build-up of solder on the tip of the iron, or it may fall onto adjacent circuitry and cause a short cir- cuit .

When soldering to an eyelet or hole on the board, insert the wire from the components side, and apply the iron to the bottom, leaving some bare wire exposed so that you can see that the eyelet is then filled with solder for a secure bond. A round wooden toothpick is suggested so that you can heat and clear an eyelet of solder if it hinders your in- serting the wire. Some builders prefer to clear every eyelet first with a touch of the iron and toothpick. Others connect the lead by bringing it up to the center of the eyelet on top of the board, applying the iron from the bottom of the board, and pushing the lead in as the solder in the eyelet melts. If the wire has first been “tinned,” usually no addi- tional solder is necessary, but it is a good practice to push the wire through, and then back it up a bit, to be sure solder fills the eyelet. On the bottom of the board, make certain a bright, shiny flow is evident from the wire onto the circuit pattern on the board.

“Tinning” refers to the process of applying a light coat- ing of solder to the bared wire end. This keeps all the strands secured, and also makes a good connection easier. Simply touch the wire with the iron for a couple seconds, and apply solder. Allow the excess to flow away onto the iron. When properly done, the wire is uniformly bright, and no larger than before. The hookup wire supplied with this kit does not normally need tinning, for it is pre-tinned.

Wiring the Kit

If any components are unfamiliar to you, checking the pictorial diagram should quickly identify them. Or, the quantities, and the process of elimination as you check the parts list, will help. The pictorial diagram is necessarily distorted to some extent for clarity, so that you can trace every wire in a single overall view for verification as you work.

To “prepare” a wire means to cut the designated length from the length of that color, and strip about l/4” of insula- tion from each end. The wire supplied in the kit is #18 and #22, so you can set adjustable wire-strippers accordingly. The transformer leads are #18, and the line cord is #16. Be careful that you do not nick the wire when you strip it (that can happen more easily if you do not use wire strippers) for that weakens it. The wire supplied in this kit is “bonded stranded,” which provides exceptional flexibility with re- sistance to breakage for easier use.

Whenever a connection is to be soldered, the instruc- tions will so state, or indicate by the symbol (S). If more than one wire is to be soldered to the same point, they will be indicated by (S-2), (S-3), etc. If soldering is not called for, other connections have yet to be made to that termi- nal. They would be more difficult if the connection was al- ready soldered. Every connection in the kit will be sol- dered when it is complete. After soldering a connection, it is best to clip off any excess lead length to minimize the possibility of a short circuit, and for neatness.

Be sure that uninsulated wires cannot touch adjacent terminals or the chassis metalwork.

When the instructions call for twisting two or three wires together, the length of wire indicated anticipates a fairly tight, uniform twist by hand, of three full turns every two inches. If you find the wires too short, loosening the twist will gain some needed length.

Take the time to be accurate and neat, and you can be sure that your completed preamplifier will meet the per- formance of a factory assembled unit, and can continue to perform properly for years to come. Check your work, and make sure the entire step has been completed before plac- ing a check mark in the space provided, and continuing on to the next step.