> "martinfriedman67" <radi...@...> wrote: > Our Amateur radio club's Motorola MSR 2000 continuous > duty amp needs repair. I cant figure out how to remove > the amp board from the heat sink. I removed all screws > from corners as well as the transistors. It seems to be > held by the center, just below the tall air variable > cap. I tried heating the solder in the area but, no joy. > I don't want to crack the board. The drawings in the > manual I found here do not show even the screw holes. > Thanks in advance, 73, Marty (WB2BEW)
Been there, done that, coffee mug and T-shirt.... It's not easy... I'm doing two MSR-2000 PA's right now (just in the door yesterday) and I completed my last MSR UHF PA repair a year or two back. Everyone has a different technique and mine depends on the specific failed stage/parts. I use a very large mass soldering iron (better than a gun) to quickly get on and off the portions I need to deal with. I reflow the solder in most of the "anchor places" using a small amount of new (solder) and lots of quick on/off, well spaced long-time to slowly cool down... between applying the iron to repeat locations. Then comes a decent amount of quick on/off Solder Wick to remove much of the original and added solder, then flat blade X-acto knives (and razors) to carefully wedge up the securing contact surfaces. Sometimes I can and do reflow a bit of solder back into the cleaned section during the flat blade lift process as a method of quickly transferring heat to a very localized area/spot. The key is to get/keep the ceramic substrate as cool as possible. The MSR Power Supply pins poke up into the substrate(s) ... The entire project including obtaining the parts from recycled radios takes me about 4.5 hours with beverage of choice and some decent AM Talk-Radio playing at low back-ground volume level (no, not the right-wing whack job stuff). Once you've had to do this type of Motorola PA repair, you more fully appreciate trying to keep the amplifier happy and cool. cheers, skipp
