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The Green Slime: Echorec Wire Rot And How To Cure It

The Green Slime? Now what on planet earth could the connection be between a high-class Binson ‘Echorec’ delay-echo machine and a low-budget 1960s sci-fi ‘B’ movie? Well, the spacey electronic tonalities of the Echorec have found their way into the sound scores and sound effects of just about every retro sci-fi movie and TV show ever produced, but that’s not it; this article is concerned with something much more sinister, insidious and… slimy.

Although the Echorec is considered by many musicians and sound engineers to be the Ferrari ‘166 Barchetta’ of echo machines, hidden deep within its metal interior there lurks a disturbing and unpleasant secret. The outside of the machine might appear to be in beautiful, near-mint condition. And internally the Echorec might seem to be clean and in good order, at first glance. But on closer inspection tell-tale signs reveal all is not well in Echorec-land. There are cracks in the wire insulation exposing copper conductor coated with a bluish-green verdigris, an oily liquid is oozing out of the wire insulation and there are ugly stains on the metalwork. The machine has wire rot.

binson_echorec_rotten_wiring_320px — Crumbling high voltage mains wiring from power inlet of an Echorec (click image for a close-up of the model 'B2' rated horror)

The Cause Of Wire Rot

Wiring degradation — The degraded plasticiser can cause open and short connections within the Echorec's wiring.

The origin of this rotten wiring problem goes right back to the day the cable insulation was manufactured. The insulation material covering the single core and screened cable in the Echorec is made from a synthetic polymer known as PVC (PolyVinyl Chloride). During its manufacture a ‘plasticiser’ is added to the PVC. The plasticiser lessens the attraction between the polymer chains allowing them to move more easily, imparting flexibility in the cable and also uprating the low temperature performance of its PVC insulation. In short, the plasticiser improves the qualities of the cable’s insulation, but it’s also the cause of the wire rot problem.

During the mid to late 1960s, specifically between 1965 to 1971, the company that manufactured and supplied cables to Binson were utilising di-isoctyl phthalate as a plasticiser. In the long-term di-isoctyl phthalate breaks down releasing hydrochloric acid from the PVC insulation. This acid attacks the copper conductor to form copper chloride (the blue green verdigris). The verdigris has a tendency to attract moisture which further corrodes the copper and this reacts with the plasticiser to form a green slime, which can become conductive in certain conditions creating low resistance paths and short circuits.

Further, the hydrochoric acid fumes will eat into and stain the steel chassis of the Echorec, corrode and damage those beautifully made Italian LESA potentiometers and other nearby metalwork, such as the aluminium housing of an electrolytic capacitor. The acid also catalyses further degradation of the PVC insulation. This releases even more fumes until the whole process runs away with itself creating a great deal of unsightly collateral damage, some of which is effectively irreparable because it’s so prohibitively expensive to put right. For instance, stains and corrosion on the chassis can only be removed by stripping the Echorec down and sending the chassis parts to an electroplating company to be cleaned and replated.

Echorec rust stain — These corrosion stains are the result of hydrochoric acid being released due to an adverse reaction between the plasticiser in the PVC insulation and the copper conductor of the old wiring.

Open circuits are created where the wire is especially thin and has been eaten away entirely by the acid, for example the inner core of the screened audio signal cables. Ultimately the PVC insulation becomes brittle, flakes away, exposing the inner conductor potentially resulting in more short circuits. Some of these wires carry high-tension D.C. voltages and can give the unsuspecting tinkerer a nasty jolt, others carry the live and neutral wires from the mains connector, as shown in in the photograph above. These are potentially lethal. Unfortunately there’s only one severity of wire rot: terminal.

The Cure For Wire Rot

The only cure is to remove all the rotten wiring and replace it with new. Be aware the rewiring job is labour-intensive work, made even more challenging because the machine needs to be partially stripped-down to gain access to avoid melting/damaging other components when trying to get in there with the soldering iron. And, it’s time-consuming work, taking two or three days to complete, that is, if you’re familiar with the Echorec and know what you’re doing. Substantial reserves of patience and resolve are required to complete the wiring to the standard it deserves.

Incidentally, before anyone goes off to rewire their precious Binson, be aware that not all Echorecs possess wire rot. The cable utilised in machines prior to 1965 was originally manufactured in Italy for Binson and reputed to be top quality. Rot is confined to machines manufactured from the mid 1960s onwards and up until at least the late 1970s. Unfortunately this was at the peak of Binson’s manufacturing production, at the zenith of the Echorec’s popularity. A vast number of machines with bad wiring were shipped out to customers and, due to the chronic nature of the problem, Binson did not detect it immediately. It was only much later, when machines were being returned to the factory for servicing, that they became aware that the wire was degrading.

The rot problem can also found in the input an output wiring of the power supply filter choke on the model ‘T7E’ Echorec. This is easily overlooked because the choke wiring is hidden behind the choke. These wires carry high voltages and can easily short on the chassis meaning it may be necessary to replace it with a modern equivalent—this should be 2 to 5H and 130Ω resistance (Hammond part# 156L). Fortunately the wires connecting to the primary and secondary windings of the mains transformer do do not suffer from rot. These wires are insulated with a harder type of plastic, possibly uPVC. Anyway, enough chat. Let’s delve in and discuss how to go about making a stellar job of the rewiring.

Getting To The Wiring

As mentioned above, attempting keyhole surgery with a soldering iron will only result in scorched wire insulation and damaged components; the Echorec must be dismantled to gain access and perform the rewiring job properly. There are literally dozens of bits and pieces to remove so it’s useful to take photographs along the way. Keep small nuts, bolts, knobs and other tiny, easily lost items from each stage of disassembly together in small labelled plastic bags. Order of disassembly is as follows:

Unscrew four bolts underneath Echorec and remove it from it’s wooden carry case. Watch out for the two aluminium spacing bars between the Echorec and the case as these will drop out now they are no longer secured by the bolts.
Unscrew the single self-tap screw that secures the lid and remove it.
Remove plastic oil bottle and four screws securing the clear plastic lid that covers the drum and heads.
Remove the memory system (mounting plate with the drum and heads), First unsolder the five signal wires to the heads and then unscrew the four nuts at each corner of the plate. These are usually cemented in position with red or silver nail varnish, however this can be softened by applying isopropyl alcohol with a small paintbrush. The mounting plate can be lifted a few inches above the main chassis of the machine to expose an earth wire connecting it to the chassis. Unsolder this and the plate can be lifted away completely.
Unscrew the small self-tap screws around the edge of the back and rear panels then remove them.
Remove knobs, light bulb covers, plexiglas front panel and nuts securing pots. This allows some movement of front panel away from the main chassis, making possible to remove/replace wires deep inside the machine.
Unscrew all jack socket washers, the screws on the mains socket and self-tap screws on side panels. The self-tapping screws securing side panels will need to be removed at some point to gain access for rewiring the the mains socket and voltage selector or when replacing ‘Geloso’ input/output plugs with ¼” jack sockets.

Choose The 'Right' Kind Of Wire

Non-braided coaxial wire — Non-braided, rather than braided, shielded coaxial wire makes the wiring job much easier.

This might seem obvious, however that initial decision about what kind of wire to use dictates whether the job goes smoothly and effortlessly, resulting in neat and tidy wiring you’ll be proud of, or making a complete pig’s ear of your Echorec. Firstly, make sure to use reasonably thin gauge multi-strand single core wire. I recommend 16 × 0.2mm stranded wire (20 AWG; external diameter 1.6mm) with PVC jacket. You’ll require two meters (2m) of each of the following colours: red, black, white, yellow, brown, orange, green. Thicker wire than this is not recommended as it will put undue stress on fragile metal parts such as solder tabs on tube sockets, transformers and the solder tags on Binson’s proprietary circuit boards which are remarkably fragile and brittle and inclined to snap off with even the slightest amount of bending. Additionally, thicker gauge wire is more difficult to route and you’ll more than likely find yourself battling with it to keep it sitting nicely in position.

Secondly, there’s also a fair quantity of screened single-core coaxial cable within the Echorec. Screened cable is used to ensure noise pick-up is kept to a minimum as the cable is carrying low-level audio signals from/to the input/output jack sockets, tape heads and channel selector switches. The Binson wire is thinner than typical instrument or microphone cable, which is normally around 6mm diameter, and several different colours (white, red, blue, green and yellow) are used, the purpose of this is to aid wire identification. Ideally the diameter of the wire should lie somewhere between 3.0 and 3.5mm, with a 16 strand inner-core (16 × 0.1mm) and 28 strand screen (28 × 0.1mm). Further, it’s desirable that the screen isn’t braided, like the wire shown in the photo, otherwise a great deal of time will need to be spent tediously picking the braid apart with some kind of pointed tool or a small screwdriver. Approximately two meters (2m) of each of colour are required.

Unbraided screened wire with different coloured jackets is very hard to come by. This is a problem if you’re undertaking an Echorec restoration and want to keep the machine looking authentic inside and out. One solution is to break down Eurorack patch-cords, which are terminated in 3.5mm jack plugs and come in different lengths and colours. For instance, Korg sell a pack of six 750mm long patch-cords (SQ-CABLE-6) with red, orange, yellow, green, blue and purple jackets. You’ll need two packs to complete the wiring job on a 6-knob ‘T7E’ Echorec. If coloured wiring isn’t a concern then you could just opt to settle for screened cable with a plain old grey or black jacket. Personally, I prefer coloured wiring as it maintains the authenticity of the machine.

The Rewiring Procedure

Rewiring is a delicate and time-consuming operation. Keep a steady hand and go slow. Replace just one wire at a time taking care not to dislodge any rotting wires. They’re extremely fragile and all too easily break and become disconnected, and if that happens then you’ll need to begin referring to circuit schematics, adding yet more toil to an already painstaking task. But, no matter how much care is taken, these old Binson wires inevitably fall apart making a mess everywhere. A little brush, like an artist’s paintbrush comes in handy to sweep away the small fragments of insulation as they constantly fall away from the disintegrating wires. It really is a labour of love to restore one of these machines back to full health.

Once a cable had been removed, measure it and cut a new piece to the same length. Strip the ends of the new cable, tin them lightly with solder and then fit it neatly into its position. It’s best to work through methodically replacing the single conductor wiring, starting around the mains transformer and power outlet. then move onto the screened coaxial signal cables. Heat-shrink sleeving can be used to shroud any exposed ‘live’ power connections from the the mains inlet, voltage selector and on-off switch potentiometer, however ‘Hellerman’ rubber sleeving is even better as it gives the completed Echorec restoration an authentic, old-school look.

Hellermann insulation on voltage selector — Use 'Hellermann' rubber sleeving to insulate the exposed bare metal contacts on the voltage selector and mains inlet socket.

Resistors And Capacitors And Other Fancy Stuff

Dissolving resistor colour bands — 'Servisol' cleaning lubricant is effective at removing dirt from switch contacts. It's equally effective at dissolving the coloured bands on vintage carbon composition resistors!

Whilst undertaking the rewiring operation it’s worth checking the ohmic value of the resistors to see if any have drifted out of tolerance, and visually inspecting the other electronic components for distress or damage. The electrolytic smoothing capacitors will have dried-out years ago, lost their ability to hold charge and function as capacitors, so they’ll definitely need to be replaced, or rebuilt. “Canned-Air” duster along with your brush can be used to blow out any dust bunnies and debris. Grime and grease is a different matter though. Be especially careful when using solvents such as Servisol® ‘Super 10’ switch cleaning lubricant and isopropyl alcohol. Super 10 is great for cleaning the multi-pole head selector switch, tube sockets and the pots too, but if it, or isopropyl alcohol, comes into contact with any of the old resistors it will rapidly dissolve their colour identification bands. Not at all desirable when restoring a vintage machine.

And these machines are well worth restoring, carefully, and sympathetically. If the resistors do happen to be particularly greasy and grimy (and it does happen with the older machines such as the model ‘T5E’) then a small, short-bristled brush dipped in diluted ethoxylated alcohol (a.k.a. ‘Flash’ floor cleaner) can work wonders to clean them. Any excess should be dabbed away immediately using paper tissues. Further, make sure all residue is removed using another brush and a little distilled water. Finally, dry it off with a hairdryer.

All this might seem over-persnickety, obsessive even, but consider this: there’s no equivalent analogue or digital stompbox that comes anywhere even remotely close to matching the depth, the richness and the complex swirl of the Echorec; the combination of Binson’s innovative magnetic drum and tubes generates a truly unique and magical delay. It is worth taking the time and effort to restore one of these splendid old machines back to it’s former glory, so restore it well.

Old 'B1' waiting patiently for restoration.

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The Green Slime: Echorec Wire Rot And How To Cure It