Michael, I measured 27volts open circuit on my Drake L-7. Relay current is around 50mA. I would suggest a "soft-key" circuit similar to the Harbach Electronics retrofit kit for the SB-220/221. The soft-key circuit is not much more than a MOSFET which has sufficient voltage and current ratings to safely switch the high voltages and currents typically associated with older amplifiers like the Heathkit SB-220/221 (120VDC open circuit voltage). With the lower voltage used on the Drake, you can probably get away with a PNP transistor (e.g. 2N3906) and a couple of resistors to buffer the relay circuit. This would be a better choice than adding an additional relay. With too many relays in cascade you run the risk of adding excessive delay to the keying circuit. This can result in hot switching of the RF relay contacts in the amplifier if the intermediate relay slows things down enough.
Here is the URL for Harbach: http://www.harbachelectronics.com/ Unfortunately, it looks like the catalog is offline for a few weeks while Jeff W8CQ moves his shop to a new location. 73 de Mike, W4EF.................. ----- Original Message ----- From: "Jim Roik" <[EMAIL PROTECTED]> To: "S. Michael Stoller" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Monday, November 10, 2003 10:04 PM Subject: RE: [drakelist] L4B and L7 > I believe the voltage is around 36 V. > > Do not try and key the amplifier directly with the pro 2. The output > contacts in the Pro2 do not have sufficient rating for the amplifier. Use a > small relay between the Icom and the amplifier. I believe that you can buy > an interface, but you just need a small relay and wet it with 12 VDC. I used > a Potter and Brumfield plugin relay. > > Failure to do this will likely cause the contact in the Pro2 to weld > together. > > Jim VA7JR > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of S. Michael Stoller > Sent: November 10, 2003 6:44 PM > To: [EMAIL PROTECTED] > Subject: [drakelist] L4B and L7 > > > Please can anyone tell me the voltage and current on the vox key line of > both the L4B and L7. Drake service cannot. > I want to make sure I do not damage an Icom 756 Pro 2. > I really appreciate any info > ---------------------------------------------------------------------- Submissions: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] - subscribe drakelist in body Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Brought to you courtesy of TLCHost.net http://www.tlchost.net/ ----------------------------------------------------------------------
