Repairing Vintage Effects

Don’t give up on that garage sale special yet!

by Craig Anderton

So you finally tracked down an ultra-rare, ultra-retro Phase Warper stomp box manufactured back in the mid-’70s. Not surprisingly, it doesn’t seem to work very well (if at all); sitting unused in someone’s garage for over a decade has taken its toll. But if you know a few basic procedures, you can often restore that antique and give it a new life. Here are some ways that have worked well for me to restore vintage effects.

OXIDATION ISSUES

One of your biggest problems will likely be oxidation, here metal surfaces become corroded due to stuff in the air (whether pollution in LA or salt spray in Maine). Oxidation shows up as scratchy sounds in pots, intermittent problems with switches, and occasional circuit failure. Fortunately, chemicals called contact cleaners can solve a lot of these problems. I’ve had good luck with DeoxIT from Caig Laboratories; they also make an Audio Survival Kit with cleaners for plastic faders and contact restoration as well as cleaning.  but there are many other types (such as “Blue Shower” contact cleaner). Here are some ways you’d typically use contact cleaners.

Scratchy pots. Pots work by having a metal wiper rub across a resistive strip, so the pot can become an “open circuit” if oxidation or film prevents these from making contact. To solve this, spray a small amount of contact cleaner into the pot’s case. With unsealed rotary pots, there’s usually an opening next to the pot’s three terminals (Fig. 1).

Fig. 1: The red line points to an opening in the pot where you can squirt contact cleaner (photo by Petteri Aimonen).

Slider (fader) pots have an obvious opening. Sealed pots are more difficult to spray; sometimes the pot can be disassembled, sprayed, and reassembled, and sometimes you can dribble contact cleaner down the side of the pot’s shaft, and hope some of it makes it to the innards.

Once sprayed, you have to rotate the pot several times to “smear” the cleaner, and also flush away the gunk it’s dissolving. After rotating it about 20 times or so, spray in a little more contact cleaner.

If the problem returns, spray again and see if that solves things. However, at some point a pot’s resistive element becomes so worn that no contact cleaner can restore it—you then need to replace the pot with one of equivalent value.

Incidentally, people often forget that trimpots need attention too—even more so, given that they’re more exposed than regular pots. Spray them the way you would regular pots, but be very careful not to spray any trimpots that adjust internal voltages. If you have any doubts, it’s probably best to leave trimpots alone.

IC sockets. IC sockets are also subject to oxidation. A quick fix is to simply take an IC extractor (these cost about $3), clamp its sides around the chip, and pull up very slightly on the chip (Fig. 2; just enough to loosen it—about 1/16”).

Fig. 2: An IC extractor can pull an IC out of its socket, but that’s not what you want to do—just pull up very slightly. This picture shows a digital chip so it’s easier to see the pins; older effects boxes will likely have smaller analog chips.

Spray some contact cleaner sparingly on the IC’s pins. Now push the IC back into its socket. Repeat this pull-push routine one more time, and the scraping of the chip pins against the socket in conjunction with the cleaner should have cleaned things enough to make good electrical contact.

Afterward, it’s important to check that all the IC pins are not bent and go straight into the socket (Fig. 3).

Fig. 3: Verify that the pins are not bent or compromised before re-applying power.

However, use extreme caution—IC pins are fragile, which is why you don’t want to pull the chip out too far, nor do this procedure too often. If you destroy an ancient IC, you may not be able to find a replacement.

Toggle switches. Rotary and pushbutton switches respond best to contact cleaners, but toggle switches are often sealed. These are not worth attempting to disassemble, but you may luck out and find a switch that does have some openings where you can squirt some contact cleaner. As with pots, work the switch several times to spread the cleaner.

Other connectors. Some effects used nylon “Molex” connectors or similar multipin connectors. Connector pins in general can develop oxidation, and are also candidates for spraying. Sometimes they lift right up from their sockets, but often there are little plastic hooks or tabs to hold the connector in place. If you encounter resistance while trying to remove the connector, don’t force it—look for whatever might be impeding its movment.

Battery connectors. Because these connectors carry the most current of anything in the effect, any oxidation here can be a real problem. Spray the connector, and snap/unsnap a battery several times.

Two other battery tips: Check the battery connector tabs that mate with the battery’s positive terminal; if it doesn’t make good contact with the battery, push inward on the connector tabs with a pliers or screwdriver to encourage firmer contact. And if the battery has leaked over the connector, forget about trying to salvage it—solder in a new connector.

BLOW IT AWAY

Most older effects usually come free with large amounts of dust. Take the effect outside, plug a vacuum cleaner’s hose into the exhaust end, let the vacuum blow for a minute or so to clear out any dust stuck in the hose, then blow air on the effect to get rid of as much dust as possible.

If you don’t do this, cleaning your pots and connectors may end up being a short-term solution as dust shakes loose over time and works its way back into various components.

LOOSE SCREWS

While you still have the unit apart, check whether any internal screws are loose—especially if they’re holding circuit boards in place. Enough vibration can loosen screws, and that could mean bad ground connections (many vintage effects use screws to provide an electrical path between circuit board and ground, or panel and ground). Try to turn each screw to determine if there’s any play. If there is, before tightening the screw check to see if there’s a lockwasher between the nut and the panel or other surface. If not, add a lockwasher before tightening the screw—providing the lockwasher teeth don’t contact something they shouldn’t.

THOSE #@$$#^ FOOTSWITCHES

Many old stomp boxes used push-on, push-off DPDT footswitches that were expensive then, and are even more expensive (and difficult to find) now. One source for replacements is Stewart-McDonald’s Guitar Shop Supply. 

ELECTROLYTIC CAPACITORS

Electrolytic capacitors (Fig. 4), which tend to have a blue or black “jacket” and are polarized (i.e., they have a + and – end, like a battery) contain a chemical that dries up over time.

Fig. 4: The two capacitors on the right are typical electrolytic capacitors. The three on the left are variations on ceramic capacitors.

With very old effects, or ones that have been subject to environmental extremes (e.g., being on the road with a rock and roll band), it can make a major sonic difference to replace old electrolytic capacitors with newer ones of the same value and voltage rating. Note that ceramic capacitors (which are usually disc-shaped), tantalum caps (like electrolytics, but generally smaller for a given value and with a lower voltage rating), and polyester caps like Orange Drops or mylar capacitors don’t dry up and last a long time.

SAFER POWER

Many older AC-powered boxes did not use fuses or three-conductor AC cords. Although I’m loathe to modify a vintage box too much, making a concession to safety is a different matter. Fig. 5 shows wiring for a two-wire cord compared to a fused, three-wire type. A qualified technician should be able to modify your effect to use a three-wire power cord.

Fig. 5: The 3-wire cord’s ground typically connects to the effect’s main ground point (usually located near the power supply).

Good luck! Your toughest task will be finding obsolete parts such as old analog delay chips, custom-made optoisolators, and dealing with effects where they sanded off the IC identification (a primitive form of copy protection). But once you restore an effect, it’s a great feeling…and when it’s closer to like-new condition, it will probably sound better as well.

  Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.