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Geloso to ¼” Jack Socket Mod

In this short article I explain how to fit ¼” mono (TS) jack sockets on a T7E Echorec. Many of the earlier Echorec models, including the T7E, T5E, B2 and “Baby” were fitted with 3-pin input/output sockets made by the “Geloso” company, an Italian audio electronic equipment and components manufacturer. I have to say right here that I do not like DIN style sockets. My lack of enthusiasm stems from the difficulties in interpreting the wiring pinout of German 5-pin connectors (ubiquitous on European hi-fi equipment in the 1960s and 70s) and the challenge of soldering all those tiny wires onto the closely spaced socket pins without creating shorts or dry joints. It always seemed to me the odds were loaded against these connectors being reliable in the long-term and in the case of the Echorec, it’s an inconvenience to have to keep special Geloso to ¼” jack adaptor cables around. I’m all for standardisation – not DIN standardisation, but jack socket standardisation – it’s a wonderful thing.

Many older Echorec machines were originally fitted with Italian manufactured 3-pin input/output sockets and require these now obscure and hard to find ‘Geloso’ plugs.

The Geloso sockets are larger than the German DIN sockets, however even though I had the correct, obscure and hard to find Geloso to jack plug leads, these were electrically unreliable causing intermittent breaks and spurious noises. Rather than investing time repairing the Geloso connector leads I simply chose to fit jack sockets in my Echorec, which meant standard patch leads or musical instrument (guitar) leads could be used with the machine. Although this is a common restoration/upgrade for the Echorec, I should point out that any modification work will ultimately reduce the collectable value of the machine. That said, the modification is completely reversible as no cutting of metalwork is required – the Geloso sockets can be reinstalled and the machine restored back to its original state if desired.

Preparation

To gain access to perform the modification work you’ll need to remove the Echorec from it’s carry case. The machine is secured by 4 large bolts underneath. To remove these you’ll have to turn the machine upside down. CAUTION: Before attempting this check that the drum is locked. The drum should be held in position by small locking screw located within the machine on the drum shaft. If the screw has been untightened at some point then the drum will fall out if the machine is turned upside down. You can check if the drum is locked by removing the plastic lid that cover the memory system and then gently lifting the drum upwards. If locked it will move a little, but you won’t be able to pull it out.

Removing the Geloso Sockets

Remove the bolts take the Echorec out of its carry case. Next the back and bottom plates of the machine will need to be removed. Unscrew the panel screws securing them. Put them in safe place – you don’t want to lose them. Now you will be able to see the back of the Geloso sockets as shown in figure 1. Next unsolder the connecting signal and earth wires from each socket. It’s a good idea to label the three input and three output signal wires with masking tape – labelled ’1′, ’2′ and ’3′ – so they don’t get mixed up when you rewire them. The Geloso sockets are secured in position with rivets. These will need to be drilled out using a nice sharp 5mm drill bit.

Fig. 1 – Geloso sockets inside the Echorec (click to enlarge)

Installing the Jack Sockets

Fig. 2 – A piece of card (an old cereal packet is perfect) is cut to size so that it fits behind the socket holes. The card is positioned inside the Echorec behind the socket holes and their positions are marked to make a template.

Fig. 3 – A template is used as a reference to mark holes on the fibreglass mounting plate.

Fig. 5 – 6mm or 10mm M3 round head hex bolts and nyloc nuts secure the fibreglass plate in position.

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