I had one once that the power control IC seemed to be doing strange things. When we looked at it REAL closely, we noticed that the plastic case around the IC was bulged and split at the top -- best estimate was that it was lightning damage.
Very hard to see at the site, easy on the workbench under a 100 watt bulb. :-) Since there's no good source for those IC's, we knew it was gone, but it got thrown in the "junk parts" box, in-case we ever needed something else off of it, and we swapped out that stage with another one from a different PA that had other problems "downstream" of that section, and away it went... Nate -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe Sent: Monday, February 23, 2009 5:29 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] MASTRII 100 watt PA question Hello Eric, Thanks for the tip. Last night, the PA failed again. I went to the site and found that the problem is in the 10 watt PA stage, possibly the IC chip or the power control transistor. I brought it home and will look at it in more detail. The strange thing was that it came back to life yesterday, just like a bad connection would cause. 73, Joe, K1ike Eric Lemmon wrote: > Joe, > > Use a magnifying glass to closely check every solder joint for cracks. Some > such cracks appear due to temperature cycling over time. I have already had > the same problem, where a PA was dead at the site but worked fine on the > bench. It was around 40 degrees at the site, but around 70 at the bench. > Sure enough, a tiny crack had opened on a PA power lead. Reflowing solder > at that connection cured the problem. > > 73, Eric Lemmon WB6FLY > ------------------------------------ Yahoo! Groups Links
