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Tim Stinchcombe's Synth Stuff


Identifying and Replacing a Leaky IEC Power Inlet

[Disclaimer stuff: note that this page deliberately does not give blow-by-blow detailed instructions on how to wire-up a replacement power receptacle—it is not difficult, but if it is not obvious to you, then you are best advised to seek help from someone to whom it is obvious, as if done incorrectly there is grave risk of damaging not only your beloved equipment, but also your beloved body (by shock, fire, mutilation, death etc.).]

There are occasional alarming reports at the Doepfer Yahoo! group of someone's A-100 'nearly catching fire', or smoking nasty-smelling fumes and the like. These upsetting occurrences are generally caused by the failure of the EMC filter in the older types of power inlet receptacles that used to be fitted to the cases, and result in a lot of brown gooey stuff being deposited at the back of the case around the receptacle, requiring the mess to be cleaned-up, and the fitting of a new receptacle. I recently bought a second-hand case which showed these symptoms: naturally I replaced the receptacle, and thought that a few snaps might be of help to others in identifying these rogue connectors.

The problem only affects really early cases, made before late 1997/early 1998—after that Doepfer switched to using a receptacle which didn't have the filter, as it turned out they weren't needed, and it also made the cases cheaper. Cases with this older type of receptacle are easy to identify, as the on-off switch is mounted separately from the receptacle, about a centimetre above it. In addition, when viewed from inside the case, the EMC filter is shrouded in a shiny metal 'can'—later receptacles, which do not have the problem, have an integral switch in the receptacle, and lack the shiny can. (Most of this detail can be found in a post to the group, originating from Dieter himself, post #3395.)

Here is a photo of the defective one I pulled from my case:

It is made by Schaffner: note there is no switch on it, and the 'shiny can' is very evident in the right-hand picture. For comparison, this is the type currently being used/fitted:

Sean Williams of monosynth orchestra has reported that it is possible to cut open the can, cut/lever away the remains of the resin and the faulty parts until just the contacts to the socket remain, and resolder the appropriate leads to them. This is certainly a money-saving solution, in return for a few hours effort. He also shows a picture of the aftermath of the filter letting go.

I elected to replace the receptacle entirely, and in order to save myself having to replace the back panel, and so as not to have any unsightly gaps around the new receptacle I put in, I spent a long time searching for one that would be as near to a 'drop in' replacement as possible, only without the filter. I finally settled for a Bulgin part, no. BVB01/Z0000/01, which I got from RS (in the UK), as part no. 352-1831. The mounting holes are the same size and on the same centres as the original, and I only needed to file a millimetre or so off the vertical edges in order to make the hole wider. (Note to do this effectively, and indeed to clean off all the sticky-stuff left by the old leaky filter, requires completely removing the PSU from the back panel, so again heed my warning at the top of the page.) The existing slot is perhaps a little taller than the new receptacle, but you have to look very closely to tell. It also has an on-off switch built-in. (One could of course buy an exact Schaffner replacement part, but they are around 30, whereas this Bulgin one was 3.) Here is the new receptacle in-situ:

Note that I left the old switch in place, which is now completely redundant, as it is not wired in at all—I figured it was better than having a small opening.

[Page last updated: 14 Dec 2009]