"Martin Sole" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- I checked the bias voltage at the tube bases. The AC4 pot varies it between about -44 volts and -85 volts. If I key the radio in SSB (No Mic gain) and advance the bias pot until the meter shows 0.1A, bias voltage measures about -55 volts,then release the PTT the current increases to approximately 0.12A.
Same problem with different PA tubes that were known good last time they were tried in another radio. Looking at the cathode line it seems this is taken to ground by a contact on K1 but when unkeyed should rise up to cut off the tubes. How many volts should be on the cathode line in the unkeyed state? On this radio the point at L5 sits around 0.38 volts in the unkeyed state and drops to 0.34 volts in the keyed state. Voltages are the same with K1 removed. Ideas appreciated. 73 Martin HS0ZED -----Original Message----- From: Gary Poland [mailto:[EMAIL PROTECTED] Sent: 06 September 2005 10:22 To: Martin Sole Subject: Re: [drakelist] T-4XC permanent current problem Martin, Sounds like you have lost a capacitor in the AC-4 bias supply. The voltage is too positive causing constant plate current. 73, Gary -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.18/89 - Release Date: 02/09/2005 -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.18/89 - Release Date: 02/09/2005 -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.18/89 - Release Date: 02/09/2005 ---------------------------------------------------------------------- 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 ----------------------------------------------------------------------
