Tech's Files: Servicing Vintage Audio Gear

Sep 9, 2010 2:18 PM, By Eddie Ciletti



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A soft wire brush is useful for burnishing tube contact pins.

A soft wire brush is useful for burnishing tube contact pins.

When a faulty instrument, line or speaker connection isn’t the cable, the crackles can be due to loose or tarnished input/output connectors. Don’t be lulled into a false sense of security by nickel-plated phone plugs. They may look shinier than brass patch plugs, but some non-conductive “films” can be transparent—almost like satin-finish lacquer. The off-the-shelf solution is to burnish the plug with a 3M Scotch-Brite scrubber pad (or equivalent).

Visual inspection of XLR males is easier when the connectors are removed from their shells. Silver-plated connectors can oxidize black, which is not only visually obvious, but can also turn the connection into a diode, rectifying the audio into a mysterious, distorted nightmare. Limited space makes burnishing XLRs a second choice to chemical treatment, aka Silver polish. I haven’t tried Hagerty products, but I have used Tarn-x and it’s very effective. As with all chemicals, heed the warning and work in a well-ventilated area.

A toothpick or bamboo skewer is handy for cleaning tube sockets.

A toothpick or bamboo skewer is handy for cleaning tube sockets.

Don’t overtighten plastic jacks; take the time to pop the cover to see that the opposite side isn’t obviously damaged (or spinning or unsoldered). As mentioned earlier, if the connector is soldered to a PCB, it’s important to inspect for both broken traces and a “cold” (weak/poor) solder joint.

If swapping tubes makes nasty crackles, the socket or pins might be dirty. A soft, fine-bristled (0.1mm) brass-wire brush (see Fig. 2) works well on tube pins. To clean the 7- and 9-pin tube sockets, start with a round toothpick dipped in anhydrous (99-percent alcohol) or denatured alcohol. (See Fig. 3.) Don’t push too hard, but do rotate. If the toothpick comes out gray-black, then it needed to be done. Follow up with a fresh pick dipped in a contact cleaner/preservative such as Stabilant 22 or Caig DeoxIT. If cleaning reduces but doesn’t eliminate the crackle, a fatigued socket or cold solder joint might be at fault. If a replacement is necessary, consider using ceramic sockets. Physically strong and with low capacitance, these are a better choice than plastic sockets.

You may not be ready to dive directly into component-level servicing, but by following a logical approach to signal flow and paying attention to simple details (such as clean connections), you’ve come a long way toward keeping your vintage gear in prime operating condition.

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