Hafler DH-500 manual Wiring the Kit

4. Allow the connection to cool undisturbed.

Remember that the connection is made by the solder, not by mechanically attaching the wire to the terminal. Usually the wire is looped through the lug and crimped in place, but some prefer to just place it through the hole and rely on the stiffness of the wire to hold it while soldering. Eyelet connections, of course, are handled this way.

Good solder connections are essential for trouble-free, noise-free operation. A good solder joint does not require much solder around the conductors. Never “butter” par- tially melted solder on the joint, as it is useless. A good connection looks smooth and bright because the solder flows into every crevice when the parts are hot enough. The iron must have a bright, shiny tip to transfer heat eas- ily to the junction. That’s why the damp sponge should be used frequently to wipe the tip, and occasionally you must add a small amount of solder to the tip, too. If a connection is difficult to heat, “wet” the tip with a small blob of solder to provide a bigger contact surface to the joint. Once the solder flows around the conductors, any movement must be avoided for a few seconds to allow a good bond. When cool, check the connection by wiggling the wire. If in doubt, or if the connection is not shiny, re-heat the joint. 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 40160, 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 solder once 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 into adjacent circuitry.

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.

"Tin ning” refers to	the process	of applying a light coat-
ing of solde r to the	bared wire	end. This k eeps 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. You may wish to check off on the diagram as you solder each location.

To “prepare” a wire means to cut the designated length from the coil of that color, and strip about l/4” of insulation 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-4), 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 (as on switch lugs, where ter- minals are very close together), and for neatness.

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

The symbol (#) indicates a connection is to be made to that point. When a lug number is specified without (#), it is simply a locating reference.

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.

Handle the circuit boards carefully. They represent a major part of the kit cost. Stand-up components, such as transistors, should be checked when you install the mod- ule, to be sure all leads are separated, and that the large electrolytic capacitors have not broken loose from the board.

Take the time to be accurate and neat, and you can be sure that your completed amplifier 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.