Topic: Keep Blowing Fuses on RC power harness

[terrapinj]

I have a DIY harness running my UA-5 and JB3 via 9.6v rc batteries set up to run in paralle, but I only run 1 battery at a time and usually use the internals on the JB3l. I have one set of wires running into a SIMA SUP-2 for the JB3 and the other set runs to a Ratshack adaptacable for the UA-5. Each set has its own inline fuse holder. I started running a 2amp fuse in each side, but noticed after a few times powering the ua-5 up that the fuse kept poping. So I moved up to a 2.5 amp fuse just for the ua-5 side, and still seem to have the problem. The fuse has never blown while recording but every so often when I try to power up it won't power and when I check the fuse its blown. I couldn't seem to find the max amp draw for the UA-5, but I did not think it was more than 2.5 amps. Should I move up to a bigger fuse still, or is there someother underlying problem that I am missing? Sorry if my lingo here is a little confusing, but any help is greatly appreciated.

[MattD]

I don't think anything we use in the field should draw 2.5A. My Metric Halo unit, which was one power-hungry machine, topped out at about 1.2A with all inputs, outputs, and phantom running.

[leegeddy]

I have a DIY harness running my UA-5 and JB3 via 9.6v rc batteries set up to run in paralle, but I only run 1 battery at a time and usually use the internals on the JB3l. I have one set of wires running into a SIMA SUP-2 for the JB3 and the other set runs to a Ratshack adaptacable for the UA-5. Each set has its own inline fuse holder. I started running a 2amp fuse in each side, but noticed after a few times powering the ua-5 up that the fuse kept poping. So I moved up to a 2.5 amp fuse just for the ua-5 side, and still seem to have the problem. The fuse has never blown while recording but every so often when I try to power up it won't power and when I check the fuse its blown. I couldn't seem to find the max amp draw for the UA-5, but I did not think it was more than 2.5 amps. Should I move up to a bigger fuse still, or is there someother underlying problem that I am missing? Sorry if my lingo here is a little confusing, but any help is greatly appreciated.

something is definitely wrong. ua5 draws less than 1A with P48. 

is this your setup?

9.6v                          ============ fuse1================ua5
       \                      /
         \                   /
          =========
        /                    \
       /                      \
9.6v                         ============ fuse2================sima sup-2========jb3

is fuse1 the one that keeps blowing?

marc

[dnsacks]

I'd up the amperage of the fuse and use a slow blow fuse.  The primary purpose of fusing the battery is to keep a short on the battery side (the harness wires connecting the battery's positive and negative terminals together) from melting the battery/causing a fire.

running some simple math, a 2, or even 2.5 amp fuse may well be too small.

 I'd play it safe and go with a 4 or 5 amp slow blow fuse and carry some spares.

[terrapinj]

I have a DIY harness running my UA-5 and JB3 via 9.6v rc batteries set up to run in paralle, but I only run 1 battery at a time and usually use the internals on the JB3l. I have one set of wires running into a SIMA SUP-2 for the JB3 and the other set runs to a Ratshack adaptacable for the UA-5. Each set has its own inline fuse holder. I started running a 2amp fuse in each side, but noticed after a few times powering the ua-5 up that the fuse kept poping. So I moved up to a 2.5 amp fuse just for the ua-5 side, and still seem to have the problem. The fuse has never blown while recording but every so often when I try to power up it won't power and when I check the fuse its blown. I couldn't seem to find the max amp draw for the UA-5, but I did not think it was more than 2.5 amps. Should I move up to a bigger fuse still, or is there someother underlying problem that I am missing? Sorry if my lingo here is a little confusing, but any help is greatly appreciated.

something is definitely wrong. ua5 draws less than 1A with P48. 

is this your setup?

9.6v                          ============ fuse1================ua5
       \                      /
         \                   /
          =========
        /                    \
       /                      \
9.6v                         ============ fuse2================sima sup-2========jb3

is fuse1 the one that keeps blowing?

marc

that is the setup marc - i am using ratshak inline fuse holders and ratshack fuses - would a slow blow fuse help the cause at all? i don't think that upping the amperage will help because I calculated that 2 amps would be plenty and even with 2.5 the same problem happens. are ratshak fuses that crappy?

[momule]

re check your wiring . Im betting you have a loose connection or a short somewhere...
 2.5 amp fuse should not be blowing running just the UA-5

[leegeddy]

I have a DIY harness running my UA-5 and JB3 via 9.6v rc batteries set up to run in paralle, but I only run 1 battery at a time and usually use the internals on the JB3l. I have one set of wires running into a SIMA SUP-2 for the JB3 and the other set runs to a Ratshack adaptacable for the UA-5. Each set has its own inline fuse holder. I started running a 2amp fuse in each side, but noticed after a few times powering the ua-5 up that the fuse kept poping. So I moved up to a 2.5 amp fuse just for the ua-5 side, and still seem to have the problem. The fuse has never blown while recording but every so often when I try to power up it won't power and when I check the fuse its blown. I couldn't seem to find the max amp draw for the UA-5, but I did not think it was more than 2.5 amps. Should I move up to a bigger fuse still, or is there someother underlying problem that I am missing? Sorry if my lingo here is a little confusing, but any help is greatly appreciated.

something is definitely wrong. ua5 draws less than 1A with P48. 

is this your setup?

9.6v                          ============ fuse1================ua5
       \                      /
         \                   /
          =========
        /                    \
       /                      \
9.6v                         ============ fuse2================sima sup-2========jb3

is fuse1 the one that keeps blowing?

marc

that is the setup marc - i am using ratshak inline fuse holders and ratshack fuses - would a slow blow fuse help the cause at all? i don't think that upping the amperage will help because I calculated that 2 amps would be plenty and even with 2.5 the same problem happens. are ratshak fuses that crappy?

ime, fuses are rarely the problem. there's something in the wiring *somewhere* in the chain that's causing the problem. 2.5amps is HUGE in the context of gear we run.  try your best to isolate the problem by 1) connecting the sima sup-2 alone (with and without the jb3 battery), 2) use a multimeter to check continuity between + and - at every point possible.  it could be your ua5 that's causing a problem. there could be a bad capacitor in the PS circuit.

i would highly suggest you don't UP the fuse size nor use slow blow fuse. fuses are blowing because there's a problem and that problem must be found.
you could also take everything apart and start over. i suggest that as well.

marc

[terrapinj]

Thanks for the help Marc - i'm gonna try your recommendations this weekend. if the problem is with the UA-5, am I SOL since its been modified (DIY) and likley not under warranty anymore?

[JAH]

I have a DIY harness running my UA-5 and JB3 via 9.6v rc batteries set up to run in paralle, but I only run 1 battery at a time and usually use the internals on the JB3l. I have one set of wires running into a SIMA SUP-2 for the JB3 and the other set runs to a Ratshack adaptacable for the UA-5. Each set has its own inline fuse holder. I started running a 2amp fuse in each side, but noticed after a few times powering the ua-5 up that the fuse kept poping. So I moved up to a 2.5 amp fuse just for the ua-5 side, and still seem to have the problem. The fuse has never blown while recording but every so often when I try to power up it won't power and when I check the fuse its blown. I couldn't seem to find the max amp draw for the UA-5, but I did not think it was more than 2.5 amps. Should I move up to a bigger fuse still, or is there someother underlying problem that I am missing? Sorry if my lingo here is a little confusing, but any help is greatly appreciated.

something is definitely wrong. ua5 draws less than 1A with P48. 

is this your setup?

9.6v                          ============ fuse1================ua5
       \                      /
         \                   /
          =========
        /                    \
       /                      \
9.6v                         ============ fuse2================sima sup-2========jb3

is fuse1 the one that keeps blowing?

marc

that is the setup marc - i am using ratshak inline fuse holders and ratshack fuses - would a slow blow fuse help the cause at all? i don't think that upping the amperage will help because I calculated that 2 amps would be plenty and even with 2.5 the same problem happens. are ratshak fuses that crappy?

ime, fuses are rarely the problem. there's something in the wiring *somewhere* in the chain that's causing the problem. 2.5amps is HUGE in the context of gear we run.  try your best to isolate the problem by 1) connecting the sima sup-2 alone (with and without the jb3 battery), 2) use a multimeter to check continuity between + and - at every point possible.  it could be your ua5 that's causing a problem. there could be a bad capacitor in the PS circuit.

i would highly suggest you don't UP the fuse size nor use slow blow fuse. fuses are blowing because there's a problem and that problem must be found.
you could also take everything apart and start over. i suggest that as well.

marc

 common Marc...lets up the fuse   no wait better yet hard wire it and the problem will surely reveal itself, but you know ...once you let the smoke out there is no more magic....OK joking mode off.

another check is to swap the load side of the fuse with each other (since these sound like replaceable fuses)....make fuse 1 feed the sima sup2 and fuse 2 feed the ua5 and see if the ua5 is still the side that blows.
 note...checking the continuinty w/ the mm is to be done w/o power applied.
with power applied move some cableing around and see if the fuse blows.

gfl
jah