Hi, Thanks for everyone's input! The problem is now resolved, a note from my Weblog follows!!
Regards Nicolas www.m1hog.com 10th July - Main Board - I investigate further; after a good few hours of wandering through various tests and a few trial and errors, I find the PA Bias is grounded, instead of showing 2.7k resistance! Which is not helping matters.. The Pre Driver Bias is OK though. I read through the emails, and chat with Sean. Further digging and checking, but no real progress. Then off for a swim, and a chance to properly consider the various email suggestions; DC voltage checking, PA shorts, removing components, failed components.. Clearly, this problem requires a hot iron and a cold beer. Looking again at the circuit diagram something is dragging the PA bases to ground, now there aren't that many components that are, or could be connected to ground, I start removing them and checking the PA base ground as I proceed. After various capacitors and the 2 PA transistors! have been removed, the ground still remains.. I look across to the LPF connection and remove Z1 (Effectively a link to part of T4). The ground to the PA base disappears.. Progress.. Taking another breather, I consider T4 (As well you might) something from the LPF side of T4 is grounding across T4? Puzzled by this; I remove one of the T4 output wires(3), and replace Z1, the base ground disappears. After some wonderment I resolder the wire and the short does not reappear. I fail to quite see the logic here, but clearly there was something odd happening with T4. A considerable time is spent cleaning up and resoldering all the removed parts, checking along the way. 4039 is once again connected to its dummy load, and tested. This time we have RF!! Looking again at the PA circuit diagram also reveals that T4 should have 3 turns on the output not 2, this could explain the slightly high current being drawn (2 turns are recommended for optimum 5 watt operation. The next task then is to take the heatsink apart again and rewind T4!! --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.718 / Virus Database: 474 - Release Date: 09/07/2004 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
