Amps
[Top] [All Lists]

Re: [Amps] Fuse holder surprise

To: Artek Manuals <Manuals@ArtekManuals.com>, "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Fuse holder surprise
From: Jim <jimw7ry@gmail.com>
Date: Tue, 2 Jun 2020 20:04:17 -0500
List-post: <mailto:amps@contesting.com>
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



_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
<Prev in Thread] Current Thread [Next in Thread>