SB-400/401 HV Capacitor replacement PCB

[Michael Waldrop]

Afternoon everyone,

Recently I wanted to replace the 2 HV filter capacitors in my SB-400. I searched the Internet looking for exact replacements. Although I ran across some "NOS" capacitors, I decided to go with current capacitors. I wanted to stay with the current value of capacitor and voltage rating. How would I do that since most newer capacitors are slightly less than 1 inch high and 1/2 the diameter of the original capacitors? Searching the Internet, I found that I would have to design the PCB. So, after test driving a number of pieces of software, I settled on one and designed the HV PCB. After carefully designing and testing for correct circuit and proper fit, I ordered two PCBs as well as the new capacitors and resistors. The new capacitors are less than an inch tall and 1/2 the diameter of the original capacitors.

The day the boards arrived, I populated one board and installed it in my SB-400. With only 3 wires to connect the board to the power supply, the installation took only an hour. The PCB works great and takes up much less room than the original capacitors plus it allows for more air to flow through the final cage for cooling, something the original capacitors didn't allow.

I am currently designing additional PCBs for the SB-400/401 that will replace  the old outdated and hard to find low voltage capacitors plus get ride of the two phenolic boards under the chassis, the ones with multi soldering tabs, with a PCB. Replacement of these two boards will have all resistors and capacitors plus the two 20ufd electrolytic capacitors mounted on the PCB. The board will also have connection points for the wiring coming to and leaving from the 2 boards. I haven't completed this part of the design but hope to have it completely shortly.

I have pictures of the HV capacitor board installed in my SB-400 if you're interested. Drop me an email and I'll send you before and after pictures.

73's,

Mike
W5RKL


 
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