Translate

Friday, 31 October 2014

WEM Watkins Copicat, repairs, renovations and electrical safety upgrades!

Minding my own business, when the telephone goes, and it's a friend with a wobbly Watkins that no longer works.


Cabinet's OK. Shabby chic. Hinges need replacing...
Obviously heavily gigged in smokey pubs! Tape path is dirty, and the heads are worn, but they'll go for a while yet.








Most of the caps in the supply are in poor condition. These two were replced, the originals being high ESR and low capacity. There were also two caps decoupling the +/- 12 volts rails. One was short circuit.
One of the main problems with the copicat, is it's lack-luster electrical safety. It was made back-in-the-day when standards were different. There's a nice metal box, the chassis of which is used to ground the audio incoming and outgoing. Now here's the issue. It's not grounded to a safety electrical earth. There's only a 2 core mains lead fitted. Now in this day and age , this isn't good enough. Not unless special precautions are taken (double insulated). This certainly isn't double insulated, and, although a remote possibility, if a live wire were to come off the motor or mains transformer, and connect with the metal chassis, the ground of your guitar would now be live. It's going to hurt, or kill. Not good. It HAS happened.

So, what can we do about it? Easy... fit a three core lead, and ground the chassis. Brilliant. Guitarist now safe. Except for the thing now hums like billy-o, because we now have an earth loop. More here.
OK, so what can we do? Remember the isolation transformer we fitted to the Ekco radio? Just the job. This will prevent any earth currents flowing , and prevent the thing humming whilst maintaining electrical safety. 

Here, I've fitted the isolation transformer , and a nice new 3-core mains lead. The Earth is secured to the chassis, using a soldered ring terminal, and a nut, bolt and star washer to ensure good contact
The tape-tensioning mechanism is stripped, cleaned and lubricated.









All cleaned up and ready for the next 30 years of service!




2 comments:

  1. Earthing is via the amplifier!!

    ReplyDelete
  2. I think the comment would be better revised to "Earthing *might* be by the amplifier" Relying on a safety electrical earth on a lead of unknown parentage, designed to carry a few uA of audio current is only going to end in disaster. Be safe.

    ReplyDelete