imported_Chris Sherman

I just replaced the power switch in my Hafler SE240 power amp. The original switch had a ceramic disc capacitor soldered across the lugs of the switch. What purpose does the cap serve? Secondly I pulled up the manuals for the Hafler XL280 and DH120 they both specify the cap at .005Uf the one on my Hafler SE240 was a .015 UF 1.6 KV. This was probably not the original Hafler part as I purchased the amp from someone who bought a lot of Hafler inventory on closeout and assembles them himself. The closest match at Radio Shack was a .01Uf either 500v or 2KV. I went with the .01Uf 500v cap. Does this sound OK? The amp works fine and the switch now lights up. Should I leave it as is? Just want to get some assurance from hafler owners that the cap is OK.
Thanks'
Chris

Chu Gai

I'm thinking it's there to catch any electrical transients from the switch opening or closing that can result in speaker pops. The differences could be due to a typo, production change, or just the previous owner needing a slightly greater value for some reason.

Felix_H

I have a Halfer SE120 sitting in my room temporarily powering my mains.

When it is on but idle, the power light flickers. When a source is played, the light remains solid red.

You could alwyas contact Musical Designs who mod the haflers.

Bob K

Chris,

The cap suppresses turn-on "thump". Ceramic should be fine -- the cap should have no effect on sound quality. If the original design specified 0.005 uF, 0.01 uF should be no problem. I tend to take no chances on voltage ratings, so you might take a look at 1.6 KVDC cap like this, which would also be closer to the original capacitance: http://www.mouser.com/index.cfm?&han...8&N=0&crc=true

Tempest Construction Pix: http://www.audiocircle.com/circles/m...view_album.php

imported_Chris Sherman

Thanks for everyones help. Most of the Haflers seem to use a .005Uf 1000V so I wonder if the 500v is adaquet, the 2Kv seems like overkill.

JohnSer

They are typically called "spark killers", and are found in many amps. If the leads are long enough, for the new switch, just unsolder and reuse old cap.

Metal Oxide Varisters (MOV), which look like a large ceramic cap, are sometimes used for a current limiter, to prevent or lesson start-up thump. These will not be across the switch, but in series with the transformer.