"Lucky" wrote in message
...

"FDR" wrote in message
...
Check the following link for some info.

http://www.belfuse.com/Data/DBObject/fuseprodguide.pdf

Schurter used to have a nicer guide for fuse selection.

I once had to specify fuse values for an application. The basic premise
is to choose a current value twice that of the maximum steady state. The
other way required measuring in-rush current for the first 10 ms, and
then calculating it from the values.

Fast acting fuses will blow quicker, so you usually have to rate them
higher to avoid nuisance blows.

It's always best to put a fuse after a power supply or source that can
produce high and damaging currents.

"Lucky" wrote in message
...
Hi guys

I have a Icom R75 and Lowe HF-150 I want to run off a Astron PSU model
SL-11a. It's 13.84V and 7Amps. Now, I have some questions please about
how to protect my radios from any mishaps from the PSU or otherwise.

Now the specs for the R75 says it's current drain at 13.80v + or - 15%
is :
Standy 0.9 Amps
Max. Audio 1.1 Amps

I bought a 2 conductor DC accessory cable that has a fuse holder on it.
I will use that to connect the PSU to the radio.
It it means anything it is 22 AWG RS part # 270-025

1] Now, what size fuse should I put in the fuse holder to make sure the
radio is totally protected from the PSU?

2] Am I protecting the radio from too much volts or amps or both? I
figured Amps.

3] I have some 250V 1.6 Amp fast acting fuses. The are 5 x 20mm GMA type
fuses. Radio Shack part number 270-1051. Are these OK? Is the main thing
the Amp rating and not the volt rating?

4] The Icom Radio comes with
3 Amp FGB fuses internally and for the DC cable. Now if the radio draws
say no more then 1.1 Amps, why are they using a 3 amp fuse? Why not 1.5A
or even 2A? Why 3A?

5] So is 1.6A too low, too high, or just good? Should I go even lower to
be sure?

6] Now, the fuse in the Astron PSU itself.
Is that to protect from volt surges or amps surges?

7] Do you think I'm going to extreme measures to protect my receivers
since the Astron PSU is supposed to be that good? I want total peace of
mind knowing I did all I could to protect them.

8] My Lowe HF-150 will use 13.80v and the same PSU also. According to
the manual it can use between 10-15V and it draws approx 300mA but I
think it's more in the 500mA range to work properly.

9] Do you think I need a different fuse size in the holder to protect
the 150 or will what I use to protect the R75 be sufficient for the 150
also?

10] What is the difference between "GMA" and "FGB" type fuses? Is it
better to use the longer ones, the mini ones or it doesn't matter?

I really appreciate the help. The guys at Radio Shack did their best to
help me but they weren't sure.
Thank you
Lucky










Hi FDR,

I think after reading all the suggestions here, I might exchange these
Fast 1.6A's for either 1.8's or 2A if that's the case. Most likely 1.8A.
I'l see.

Thanks
Lucky


By the way, do these fuse holders have a polarity where they need to be
soldered in line properly?
No of course not since you can put the fuse in the holder in either way or
direction. Just figured I ask. I mean if you're not 100% sure but are 99
9/10% sure, why not close the gap on that 1/10th and ask eh?

Lucky