If one compares the current handling capability of disc ceramic caps vs doorknobs, a difference will be observed.? And, it almost goes without saying, the TV doorknobs should never be used in a linear amplifier, they can handle the voltage, but certainly not the current.
-----Original Message----- From: Dennis Monticelli <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] Sent: Tue, 23 Oct 2007 10:55 pm Subject: Re: [drakelist] L7 Capacitors Needed "Dennis Monticelli" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Another option is to use a transmitting ceramic capacitor of the doorknob variety. The smaller ones are typically rated at 5KV and built to handle much higher current ripple than a typical bypass cap. Their RF qualities are excellent. I mention this because these small doorknob caps are often found in junk boxes and at hamfests selling for very reasonable prices. There may be somebody on the net with something in the 500 to 1000pF range or if you ask some friends a unit may turn up. If I were you I would replace both bypass caps with a single transmitting cap in the 1000 to 5000pF range...basically whichever value you find. A single doorknob will probably outperform two paralleled discs. I noted in my L7 schematic that Drake also used two in parallel to do plate blocking from the PA tubes to the output network. Clearly, Drake was shaving nickels buy using a single part type multiple times to lower purchasing costs. Two HV discs cost a lot less than a single small doorknob anyway. Dennis AE6C On 10/23/07, Dino Papas <[EMAIL PROTECTED]> wrote: > > Dino Papas <[EMAIL PROTECTED]> made an utterance to the drakelist gang > ---------------------------------------------------------------------- > A friend's L7 gave up the ghost mid-QSO with the self destruction of > one of the two disc ceramic 760pF caps that bypass the HV line at the > cold end of RFC5. They're rated at 4KV....anyone know of a good > source for replacements? Also obviously gotta discover what made one > of the two fail. RF Parts has some 0.0005 uf 10KV disks that may > work in this application. BTW, his L7PS is fine as tested with his > L-4B after the L7 failure. > > Thanks much in advance! > > 73 -- Dino KL0S/4 > > ---------------------------------------------------------------------- > Submissions: [EMAIL PROTECTED] > Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body > Hopelessly Lost: [EMAIL PROTECTED] - help in body of message > Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net > ---------------------------------------------------------------------- > ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ---------------------------------------------------------------------- ________________________________________________________________________ Email and AIM finally together. You've gotta check out free AOL Mail! - http://mail.aol.com
