> "Gary" <[EMAIL PROTECTED]> wrote:
> My MSR has the TLD2532A 110 watt intermittent PA. NCD
> is more my terminology (non continuous duty) than
> anything else. I got into the habit of refering to
> an intermittent PA as non continuous duty (NCD)
> by hanging around another tech that used it.
> He was also the one that filled me in on MSRs' PA
> history. (however right or wrong the info was)
No problem Gary...
Heat is a killer of electronics... your pa is
continuous duty, just at reduced power levels.
People don't realize any reflected and high foward power
results in fast heat build up. The low duty cycle pa
has a problem with heat build up in lock to talk
(repeater operation).
> I was running my first PA at 60 watts when it failed.
Were the power control board V-limit and I-limit pots
properly set? It should have shut itself down when
trouble started.
> The only thing different that I'm doing now than
> before, is I am using fans to blow air out of the
> cabinet top side vents, plus a fan blowing across
> the PA heat sink fins. Before, I was just blowing
> accross the heat sink fins only. I'm not sure how
> efficient the PA heat sink fan is, because I had
> to do some creative engineering to get a fan mounted
> to blow up the fins from the bottom.
Sucking air up and out of the MSR Cabinets, through
the top side air vents is the best option. You can
remove the cabinet lid and covers without a lot of
grief. It takes the proper size torex bit and ratchet.
I use small metal bar stock to mount small ~4 or 5
inch dc fans across the vertical rails at the vent
level. The cover slips right over the fans, which
are triggered by extended cos logic and a timer.
> My site owner requires repeaters to be in cabinets
> with covers on, and you would know how little room
> there is to get a fan mounted to blow on the MSR
> PA with the front cover on the cabinet and still
> do some serious air movement.
Your site owner is smart... yes, I know about the
limited cabinet room. Hence the above fan mounting
information.
> It does work and looks somewhat professional.
> This repeater was getting heavy use at the first
> PA failure, but now not as much use. This may
> have something to do with its'longevity now.
> Gary KB7TRP
73's Gary,
skipp
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