"Peter Hoon" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Need any and all diagnostic suggestions from list members who are familiar with the TR4.
A blind ham, Max N0HU, will be bringing his TR4 with AC4 pwr supply to our QTH repair bench Aug 17th, with a complete set of spare tubes. Unfortunately, cannot get my hands on a readable schematic or block diagram until Max arrives with his printed manual (and we can enlarge the pictorials on a zerox machine). Max reports that he gets (what appears to him to be) normal output on SSB, good SSB and AM receive, but no AM transmit. 1) Could it be that he missed the instruction from the manual that says: "For AM operation, set function switch to X-AM position, and set sideband switch to position X."? 2) Will test Max's AC4 power supply for ripple, correct bias and HV DC under load. Though it seems unlikely, since SSB is working, could his AM problem be due to AC4 not holding voltage under load (bad caps)? We have the AC4R recap kit from Mike, ready to install if necessary. 3) Is another likely culprit a bad screen modulator tube, 13DE7? Other possible tube culprits to check? 4) Could you still get some SSB operation, but no AM, if one or more final 6JB6 tubes is bad? 5) Please send on other immediate (and less immediate) diagnostic hunches to check out, so we can hit the ground running, for this lack of AM transmit problem. We will report progress notes to the list as we work on the TR4 next week. Ultimately, we hope to do a complete voltage check out and alignment check, re-tube where necessary, since Max will be here for 3 days or so, testing the rig, but it would be great if we could quickly solve the AM problem straight off, which is our first concern. (We have a complete bench set up of test equipment: scope, transconductance tube testors, VTM, counters, dummy loads, the alignment cap and resistor suggested in the manual, watt meters, etc. All suggestions and ideas appreciated.) 73s, Peter, VE1CHS, Nederland, Colorado ---------------------------------------------------------------------- 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 ----------------------------------------------------------------------
