Sprague Powerlytic 36DX + soldering on terminals

[starbase218]

Hello,

I have four of these capacitors, which are rated at 37000uF/75V. I use them in my DoZ amp. I am in the process of upgrading this amplifier. One of the things I want to improve is the power supply. In particular, I'd like to improve the connection to these caps. Right now, I use screws and U-shapes pads to make the connection, which is less then ideal.

So I want to solder the wires to the terminals directly. However, I don't know if the material used in the terminals is suitable (i.e., aluminium won't make a good soldering joint at all). Does anyone know if this is possible with these caps?

[pinkmouse]

There is nothing wrong with a good screw connection. Can you post a pic of your existing setup so we can suggest improvements?

[jacco vermeulen]

Spring washers and screws are much better than soldering, i wouldn't even attempt it. My preference goes to the power bar system with soldered lugs that ML has been employing for two decades.

[starbase218]

Originally posted by pinkmouse
There is nothing wrong with a good screw connection. Can you post a pic of your existing setup so we can suggest improvements?

Here it is.

I used brass screws and nuts. The wires were mounted in U-shaped spades, which were mounted under the nuts.

I would think the added resistance of a) mounting the wires in the spades and b) mounting the spades using the screws/nuts would be worse than just soldering the wires into the terminals directly.

[poobah]

Don't do it. Aluminum doesn't solder without major tricks. And don't use excessive torque on the screws. Spring washers are your friend.

Use ring terminals for your connections and solder them to the wire... make sure your rings are clean and install them directly over the posts followed by a flat washer, a spring washer, and a screw. A properly made connection will probably have resistance in the microOhm range... far, far less than the internal resistance of the cap.

[starbase218]

So the terminals are made from aluminium?

[poobah]

I believe so... this allows a welding operation for the terminals and internal connections of the cap. Aluminum is often tin plated, which makes soldering considerably easier... but you still don't do it on big caps because the heat damages the rubber seals.

[mzzj]

Originally posted by starbase218



I would think the added resistance of a) mounting the wires in the spades and b) mounting the spades using the screws/nuts would be worse than just soldering the wires into the terminals directly.

Use separate spade for "input" and "output" of terminal. With inputs and outputs I mean bridge-side wiring and amp-side wiring. Or better yet power-bars made from copper plate.

[starbase218]

Ok, I'm not going to solder directly on the terminals anymore. Instead, I have cut off the screw heads in the picture using a Dremel-like tool, so now I can use a bar to connect two caps .

I also bought a brass bar, thinking that, since it is an alloy of copper and zinc, it should have fairly good conductivity. However, according to this page it's not very good at all (even zinc is listed as having better conductivity).

I'm now thinking about using aluminium instead of brass. It isn't as good as copper, but it's probably a lot easier to get my hands on.