Stuffing!

Old wax paper capacitors are notorious for going leaky. Even if they are not significantly leaky now, you can guarantee that they will be at some time in the future. My approach is usually to change all such capacitors on sight, and this receiver will be no exception to this rule.

Unusually, in the R1155, the decoupling capacitors are all housed in aluminium cans bolted to the chassis. Most of these have three 100nF capacitors inside, others have only one. I want to preserve the original appearance of the chassis, so I will be removing the contents of these cans and replacing them with modern components.

One of several capacitor cans

Removing a can from the chassis is easy. You just cut the existing wires close to where they enter the can, leaving the wires connected so you can see where you have to connect the new wires. Undoing the nut and pulling the can from the chassis completes the easy part of the task!

At this point you have a choice in the method for opening the can. Some people use a pipe cutter to separate the cylindrical part into two pieces, and then glue it back together afterwards using epoxy. Foil tape can be used to hide the join. Others may use a hacksaw to remove the end of the can, and glue that back in place afterwards. 

Fortunately I discovered an easier and neater way to do it.

Once the capacitor can has been removed, put the nut loosely back onto the threaded part. Clamp the nut in the jaws of a small bench vice with the capacitor standing vertically upwards. Now grab the end of the can and carefully rock it back and forwards, and side to side.  The cylindrical part of the can is crimped on to the threaded base part, and this rocking motion will loosen the crimping.  The trick is not to be too rough and tear the metal! Carry on this gentle loosening process until you can pull the can vertically upwards and separate it from the threaded part, which stays in the vice.

Removing the original capacitors from the can. Messy!

Carefully dig out the black pitch from the open end of the can with a small screwdriver. The now exposed capacitors inside need a bit of persuasion to come out of the can.  I use a large wood screw to do this; just screw it into the waxy yellow mass inside the can and pull it out.

In the next blog entry I'll tell you how I re-stuffed this can with new capacitors and re-assembled it.

Keep listening!