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Item Code: WCA4
WCA4 Copper Cap Item Code: WCA4

WCA4 Copper Cap

  • 9-pin Copper Cap. Replaces 6CA4/EZ81. Vdrop: 28V @ Imax: 150ma

FOR USE IN GUITAR AMPS. Not designed for use with HIFI tube amps, tube radios, etc. Drop-in Replacement for 6CA4/EZ81. Voltage drop: 28V at Maximum Current: 150ma.

Technical Details


To install the Copper Cap rectifier, simply remove the existing rectifier and replace it with the Copper Cap. Make sure the tube rectifier is cooled down before you remove it.


Weber Copper Cap Rectifiers are solid state rectifier replacement devices for use in place of vintage tube rectifiers. Each model emulates the forward conduction resistance curve of the tube type it replaces and also has linear in-rush current limiting to simulate the warm-up of a tube rectifier, however, it is in the 1 to 2 second range, rather than the 7 to 9 seconds of a typical rectifier tube. The envelopes are solid hard-drawn copper with a high thermal capacitance that allows a 100% continuous overload condition.

Why use a Copper Cap?
The Copper Cap emulates a tube rectifier, but it does not require filament power. In the case of a 5U4, for instance, this is a savings of 15 watts. The power transformer will run cooler and last longer. While the filament and coating on the cathode of a tube rectifier are destined to eventual failure, a Copper Cap will last the lifetime of the amp when used properly. Additionally, close tolerance parts are used in all Copper Cap models; no hand sorting is necessary.

How does the Copper Cap work?
It is a combination of diodes, power resistors, and other circuitry that emulate the warm-up and operating curve of the tube type rectifier it replaces.

Are the Copper Caps drop-in replacements or do I need to make changes in the wiring?
All octal-based Copper Caps are drop-in replacements. Because they don't require filament power, the 5 volt filament source may be either left connected as is or disconnected and used for some other purpose.

Can I use a Copper Cap in an amp that doesn't have a standby switch?
Yes, the inrush current limiting prevents large current surges from occurring.

What about the peak currents that occur when the filters are in the charging cycle?
The combination of the conservative power rating of the Copper Cap and the high thermal capacity of the copper envelope prevent any stress problems from transient power pulses, etc. Plus, all Copper Cap models are rated for 100% overload.

Do I have to do anything special to use a Copper Caps?
The octal-based Copper Caps are about twice as heavy as a standard glass-envelope vacuum tube, so you should ensure the tensioning on the rectifier socket in your amp is correct, particularly in the case of Fender amps where the tube hangs upside down. No other precautions need be taken other than to make sure you give it plenty of time to cool down as you would a tube before removing it.

What are the PIV ratings of a Copper Cap?
Octal and Module Copper Cap models are rated at 2,000 PIV. 7 and 9 pin Copper Caps are rated at 1,000V PIV.