7 Fixes For Older AVL Gear

From cleaning contacts to replacing capacitors, try these easy repairs for glitchy gear

Unlike a fine wine, electronic gear doesn’t always age well—you might pull out a unit that was working fine a few years ago, but no longer works. Don’t panic! The fact that it did work means the problem is probably not too severe, so one of these seven simple fixes may be all you need to help get your gear back into operation.

But first, remember this word: iatrogenic. It means an illness caused by medical examination or treatment, and it’s all too easy to have that happen with repairs! A dropped screw, a delicate plastic retainer on a ribbon cable connector that gets broken off, stripped screw threads, working on gear while it’s plugged in (even if the power switch is off), not wearing a grounding strap to avoid static electricity damage…be very careful when taking something apart and putting it back together again. Check for service manuals online, as this may help prevent an expensive mistake with gear that’s inscrutably difficult to take apart.

1  Bad Backup Battery

This one’s easy enough: replace the battery. However, remember that batteries can leak. One way to head off an expensive repair is to check internal backup batteries periodically to make sure they’re in good shape. A leaky battery can ruin your day (Fig. 1).

Figure 1: Preventive maintenance is the best kind of maintenance—this leaky battery destroyed the gear beyond repair.

There are also two fine points. First, if you take the battery out to test it, the voltage may seem fine; but when under load, it’s low. If possible, always measure the battery voltage with the battery connected. Second, battery connectors can sometimes get corroded. Scraping the battery connector slightly so that it’s shiny instead of dull may be all that’s needed to get the unit working again.

2  Blown Fuse

An external fuse is easy to check, but to check for internal fuses, you have to open up the gear. When taking the fuse out of its holder, be very careful not to break the glass shell. And when buying a replacement fuse, get two—and affix the second one inside the box (duct tape works great if the insides don’t get hot). Then the next time a fuse blows, you’ll have one handy.

3  Corrosion on Jacks

For some reason, this seems most common with RCA jacks, but can also happen with other types of connectors. With any kind of corroded metal-to-metal contact, Caig DeoxIT D5 (Fig. 2) is your friend. Many a piece of gear that seemed like it couldn’t pass signal came back to life by simply spraying contact cleaner into a jack and plugging/unplugging/rotating a plug several times to spread the contact cleaner over the surfaces. Note that you don’t need to drown the contact in cleaner; a little goes a long way.

Figure 2: This is one of my all-time favorite pieces of “gear,” because it solves problems.

And here’s a bonus jack tip: if a 1/4” phone plug is left inside a phone jack, sometimes the phone jack contact stays in that “opened” position instead of springing back upon removing the phone plug. This can lead to an intermittent or inconsistent connection. Bend the jack’s contact inward, gently, so that it makes firm contact with plug tips.

4  Corrosion with Sockets

One of my most baffling fix-it jobs was an old synthesizer. Long story short: an integrated circuit’s pins were a dissimilar metal compared to the socket into which the pins inserted, and a small, crystalline, metal “hair” grew across two pins, shorting out the IC. Brushing it lightly with a dry toothbrush got rid of the hair, which fixed the problem. But simple corrosion can also happen between pins and sockets, including ribbon connectors. With ICs, insert the blade of a small, thin screwdriver under the bottom of an IC (usually one of the ends hangs over the socket a little bit), preferably between the IC and its socket. Push the IC up about 1/16”—just enough to raise it slightly out of the socket (Fig. 3), then push it back down again into the socket.

3_Lift IC
Figure 3: Lift up on ICs, then re-seat, to wipe the contacts.

If possible, do the same thing on the other end of the IC. Raising and re-seating the IC wipes the connection between the pin and socket, which reduces corrosion.

The same technique can also work with ribbon and Molex-type connectors; with these, I usually lift the connector completely out of the socket and then plug it back into place. Some connectors have lips or retainers that prevent pulling the connector off, so you may need to push or pull on the retainer to free the connector. However, be very careful with the paper-thin, flexible kind of ribbon connectors that are held against circuit boards with plastic retainers. These are rarely the problem and are best left alone unless you really know what you’re doing.

5  Membrane Keyboard Fixes

Many membrane keyboard designs are based on conductive plastic that sits above the traces on a circuit board. Pushing down on the plastic completes the connection, but if the plastic or circuit board trace becomes dirty, the contact can become intermittent.

Sometimes it’s possible to take the unit apart to where you have access to the conductive plastic switches, for example, by unscrewing the circuit board with the traces that sit underneath the switches. Soak a cotton swab in 90% isopropyl alcohol, and use it to clean off the bottom of the conductive plastic (Fig. 4). Also, swab the traces on the circuit board that the switches contact.

4_membrane switchs
Figure 4: If you can access a membrane switch’s conductive plastic (circled in orange) and circuit board traces, you can often restore the switch operation to like-new condition.

And by the way, you may hear of people who scrape the circuit board traces lightly to clean it. Don’t! Those traces are thin, and even a little scraping can cause permanent damage. Also, if the problem is crud on the plastic switches, scraping the circuit board won’t help.

6  Bad Electrolytic Capacitors

This gets more difficult, because it may require soldering skills, and more disassembly than you’d like—but electrolytic capacitors can age, and eventually fail. In some cases, this isn’t visually apparent, so unless you know how to test capacitors in-circuit, you won’t be able to do a fix. However, sometimes there are visual cues, like a capacitor that’s swelled out, or possibly even one that looks singed or burned. Replace the capacitor with a similar value.

If the capacitor has burned, you may not be able to read its value. But look closely at the circuit board—the value may be printed on the component side.

7 Intermittent Controls and Switches

We all know that when a volume control sounds scratchy, a little contact cleaner can clean up the sound (unless the problem is a leaky AC blocking capacitor that passes DC—no contact cleaner can fix that, so you need to replace the capacitor). But if a control doesn’t pass audio, then we don’t have an audible indication that something is dirty. So if a control or switch seems intermittent, before thinking you need to replace the component, first try some contact cleaner. Note that conductive plastic faders require a different type of contact cleaner, and there are also cleaners optimized for gold contacts. The Caig Labs SKAV35 Audio/Video DeoxIT Survival Kit is well worth having around, because it includes all of Caig’s essential contact cleaning products, including wipes. And no, I don’t get a cut from Caig for mentioning their products—but when one of their sprays fixes a problem, I get gratitude from readers!

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