Most power supplies are fully current limited and the load does not need
a fuse.
Motorola never used a fuse between the power supply and the amplifier on
any VHF UHF, or 800/900 MHz power amplifier. They relied on the AC
fuse/braker to trip.
If a battery was involved, it was always (and still is) fused.
That's my point. OK?
Thanks
73
Jim W7RY
On 6/2/2020 8:05 PM, Artek Manuals wrote:
I dont recall at the moment ...what is your point?
On 6/2/2020 9:04 PM, Jim wrote:
How about during normal operation? What power supply?
Thanks
73
Jim W7RY
On 6/2/2020 7:48 PM, Artek Manuals wrote:
During the Bench testing I have an Astron R-35 more than up to the
brick's challenge of 10-15 amps and fairly short power cable less
than 18"
Dave
NR1DX
On 6/2/2020 8:38 PM, Jim wrote:
What are you using for a power supply to run this amplifier?
Thanks
73
Jim W7RY
On 6/2/2020 7:33 PM, Artek Manuals wrote:
This is going to seen trivial to many of you but some times the
most puzzling problem has the most simple solution, worth sharing.
The " 60W-brick" ( an old Mirage C106) on the 220 "lets chase
DX"-repeater had given up the ghost. No power on light ...hmmm
checked and the fuse on the back panel fuse holder� looks
absolutely perfect. So out of the rack and back to the home shop
for a more detailed autopsy. After 5 minutes of poking around with
the VOM it seems the fuse is actually a zombie fuse, meaning it
looks OK but in reality it is open with no sign life or the cause
of death, usually 15 Amp fuses die pretty spectactularly. Oh well
pop in a new fuse and it is off to the races. But the amp is only
putting out 40-45 W and it is supposed to be 60W? Playing for 10
more minutes and nothing seems out of the ordinary..oh well it is
30 years old anyway button it up and move on to the next project
right? As I put the cover back on I happen to absent mindedly
tighten the fuse holder cap and it is VERY WARM ...now wait a
minute fuse holders aren't supposed to be that warm? Further
measurement shows� a little better than .5 volt drop across the
fuse holder under load. A little loosen-tighten cycles and it is
down to .25 volts . Upon closer inspection the spring inside the
fuse holder looks dark and crusty ( like the one in your flash
light after the batteries leak). So I have some really nice fuse
holders in the junk box with bright shiny copper insides , replace
the fuse holder , no more voltage drop and the brick is at 70W out.
The moral is the old fuse holder was corroded internally to the
point that it's contact resistance had gone up enough under load
to heat the fuse contact end and melt the solder inside the fuse.
The bigger take away is that if something seems a bit odd keep
looking. This one was easy but in 50 years of tinkering I had
never seen a bad fuse holder and now I wonder how many I over
looked over the years 8^)
Dave
NR1DX
manuals@artekmanuals.com
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