There were two different PA decks on the MSR2000. One that was rated for
continous duty and one that was not. The non-continous duty UHF PA is a
real problem. It is not at all unusual to have cronic problems with it.
The DC distribution is done on a circuit board that runs under the PA modules.
The DC is broght up to the modules by way of jumpers made from square wire.
The connection between the DC distribution board and these squre wires is very
problematic. The only way to fix it is to completely disassemble to PA deck,
desolder every connection, clean everything, and then resolder all of the
connections using silver solder. This is a very involved job, and will
result in a
PA deck that will work for a few years before it is necessary to repeat the
repair
again.
Another problem area is the interconnection straps between the various stages
in the PA. Each strap should have a small "hump" in it. In other words, it
should
not be a flat strap between the substrates. The "hump" will allow for small
amounts of movement between the substrates as the PA deck heats and cools.
If you have the flat straps, the solder connections will eventually fail
and the
connections will be intermittent.
The receiver in your machine is basically a Mitrek. One thing to look for
that can
cause intermittent problems are the ground connections on the coils in the
front
end casting. The joints can fracture and cause very intermittent RX sensitivity
problems. Don't over look the two injection filter resonators that are part
of this
assembly. Get a friend and a couple LARGE soldering guns and resolder all of
these connections. It will take a large amount of heat, but make sure that the
solder flows properly and that the entire joint is fluid before you remove
the heat.
Following this repair, be prepared to touch up the aligmnment on the front end.
I hope this is useful information for you. Good luck, and 73,
Kevin, K9HX
At 09:00 AM 9/7/2004 -0500, you wrote:
>I have an MSR2000 on 444.550 for the local ham club / county EMA. The PA (a
>110W model) is out again. We just had this repaired by the local Motorola
>shop, with whom we've had very good results from in the past. We're running
>the PA at about 80W, so I'm thinking we didn't "burn it up", but I can't
>help but wonder if there is anything inherently wrong with the MSR2000 PA
>for UHF. This is the third time the PA has failed in this particular
>machine in about a 2-year time frame. (This was a repeater originally tuned
>for 460 MHZ, and brought down to the ham band.) This particular machine has
>been a pain in the @$% - RX sensitivity isn't what it should be, PA keeps
>going out, etc. Seems like we're up at the site every couple of months do
>make some sort of repair on it.
>I'm wondering if we should just cut our losses and get another machine, or
>should I keep plugging away at this repeater? If we do decide to chuck it,
>how much can I expect to spend to get a comparable replacement - we use this
>machine during severe weather season for forwarding reports to the NWS, and
>it's open other times. We want to add remote RX sites (you've probably seen
>my inquiries about those in the past) but I don't want to start adding
>remote RX sites until I get the main repeater working reliably.
>I'm open to suggestions...
>Thanks,
>Mark - N9WYS
>
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>
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