Thanks, George, for the chart. Today I put the board on the bench and applied power as noted in the manual for bench testing. First thing I tested was the reference voltage and lo and behold it was wandering around (light bulb above head begins to glow!).
Close inspection of the ref voltage components revealed a dark discoloration of the board and a general corroded look to the solder connections. Looks very much like cold solder joints. The rest of the board connections are all shiny. (bulb is getting brighter) Also the "tinning" on some of the PC traces was etched down to copper. A few minutes work with an acid brush and some alcohol cleaned up the gunk on the board and the joints were all touched up with a soldering iron. (Bulb fully on!) It has been running on the bench for 5 hours and the reference voltage hasn't budged from 6.5v !! I will install the card back in the power supply this week and see if our voltage problem goes away, and it carries the repeater load. Interestingly enough our initial indications of a problem was when the repeater would drop off the air . We thought the problem was with the PA, since we could still see some drive coming out of the exciter. Eventually it completely failed, but not until after we replaced the PA only to see the same problem come back. Oh well, we now have a spare PA! As the NTSB would put it: Probable Cause - corrosion of solder connections due to caustic substance. To put it plainly - mouse droppings/pee! We had the same thing happen to an RC-850 controller a few years ago that nearly killed the board. The repeater is in an unheated building in a field away from other structures (it is a microwave tower that the Navy lets us use), so the mice seem to like the warmth. Next project is to make a mouse shield for the repeater box! I'll let you know how it turns out. We are hoping for K3HKI = 1, Mice = 0 73 de Tom/W4OKW Pax River George Henry wrote: > Attached is the troubleshooting chart for that PS... maybe it will be > of some help. > > > > ----- Original Message ----- From: "Tom Clarke" <w4...@md.metrocast.net> > To: <ka3...@att.net> > Sent: Saturday, January 02, 2010 10:25 PM > Subject: Re: MSR2000 Power Supply part needed > > >> Hi George, >> >> Thanks for the tip. We already tried that with no joy. R7 just moves >> the voltage +/- .5v or so around 8.5 so the problem is probably >> upstream. We also are not getting the 9.3v on Tx, but that may be >> related to the 14 v reg problem. I need to go back and look at the >> 9.4v reg also to see if it is working OK. >> >> I have looked at the reg card and don't see any obvious crispy critters! >> >> 73 Tom/W4OKW >> near DC
