[Amps] Fuse holder surprise

[Jim]

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 at artekmanuals.com
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>