Electronics...all the bits nobody (well mostly nobody) really cares about.

[finga]

Here ya all go.
Start putting all the unless crap, I mean information, that nobody else wants to know about radios and electronics and sounders and GPS's and...and.. in here.
Let your frustrations out. Let your hands go nuts on the keypad.
Don't be embarrassed. If there's something on your mind let it out. You know you want too.
Hell, tell me about your multi-meter or your screwdrivers or your side cutters and coax strippers if you want. I don't really care.

Fill this thread with information that will even make Marconi and Brattain and Hertz and Faraday and Maxwell and Galvani and, and my personal favourite, Ohm think twice about what they've done to us.

Actually this will probably be better then those little green pills I have to make me snooze.

Go nuts guys

[Spaniard_King]

OK.. What on earth happened to this??? the fuse didn't blow (correctly installed with a 3 amp fuse)
pulled it from a clients boat.. unable to find his receipt so we never worried about warranty...don't recon it ever fired a shot either

[foxx510]

Power wires reversed at the factory?

EDIT: Or +12v on the antenna shield.

[TheRealAndy]

OK.. What on earth happened to this??? the fuse didn't blow (correctly installed with a 3 amp fuse)
pulled it from a clients boat.. unable to find his receipt so we never worried about warranty...don't recon it ever fired a shot either

If I could take a look at it in real life I could tell you!

But, looking at the photo it appears that the negative wire is burnt. Given that the coax is shield is probably connected directly to the radio's ground perhaps the coax shield was shorted to a power terminal. That would explain as to why the fuse is not blown.

[Spaniard_King]

does anyone think it would take more than 3 amps to do this.. if you do think that why didn't the fuse blow???

[TheRealAndy]

does anyone think it would take more than 3 amps to do this.. if you do think that why didn't the fuse blow???

If power was flowing (conventional current flow for the nerds) from coax shield through the negative wire the fuse is exluded from the circuit. Most radios I have ever worked with have the negative wire connected directly to the coax sheild, via both the PCB and the chassis.

[Spaniard_King]

There is no other power source connected to this radio so I can't see how the + was excluded from the circuit

[oldboot]

Because the fues is in the positive line and only the negative line is burnt.

yep it would be quite a bit more than 3 amps to do that.

Quite a lot of commercial two way radios in the past used to have fuses in both power wires.


The most obvious cause would be reverse polarity with the aerial shield grounded.

If you are very very very lucky it may just be negative lead gone open circuit ( fused).
No point speculating... radio workshop...... you have a good offer from Andy

Or seeing as this is suposed to be a silly thread

The cases of those radios are suposed to be pretty well sealed..... there was an excess of smoke build up within the case so the logical place for it to come out is thru the black wire........of course once you let the smoke out the item is unlikly to work.

cheers

[foxx510]

There is no other power source connected to this radio so I can't see how the + was excluded from the circuit

If the antenna shield was accidentally shorted to +12v the fuse would be bypassed.

[TheRealAndy]

What did you do with the radio? I am planning to be on the tweed the weekend before christmas, so I could take a look then if you have not binned it. Most power issues like that are easily repaired, chances are there is no damage at all to the radio.

[jigsnreels]

Ok here's my thing with electronica: how come these people can be so bloody clever they can make radios so we can talk to one another, sonars so we see fish in deep deep water, gps and maps that work from satelites up in heaven somewhere, and it all works pretty well 99% of the time but.... they can't manufacture a decent piece of plastic to hold said item securely in place???

[TheRealAndy]

Ok here's my thing with electronica: how come these people can be so bloody clever they can make radios so we can talk to one another, sonars so we see fish in deep deep water, gps and maps that work from satelites up in heaven somewhere, and it all works pretty well 99% of the time but.... they can't manufacture a decent piece of plastic to hold said item securely in place???

Thats the industrial designers job, not the electrical engineer and that is where the problem starts. If it were up to the elec engineer to do the casings and mounts the device would be the ugliest piece of machinery in the world, but they would work well. The industrial designer tries to make a good looking but functional piece of gear.

[finga]

It's on a platey with a crook wire to the bilge pump.
When the pump is turned on the positive shorts through to the hull and joins up with radio case and goes through the negative wire to the negative link under the dash to the negative terminal of the battery as it's a good low resistance path. But, alas, the wires to and fro from the radio are teeny weeny tykes so the wire melts.
Bilges are not 3A fuses and sometimes they're on slow trip breakers on larger boats.
I remember a bloke not even putting fuses in bilges for some reason or another.
PS the radio is probably still okky dokky but needs a new wire.
PPS or it could be that the outer plastic covering on the aerial coax has a bare spot to expose the shield and rubs up against the positive bus somewhere. But that doesn't sound near as impressive
PPPS There's a lot of flaws in the first theory. What are they?

[TheRealAndy]

It's on a platey with a crook wire to the bilge pump.
When the pump is turned on the positive shorts through to the hull and joins up with radio case and goes through the negative wire to the negative link under the dash to the negative terminal of the battery as it's a good low resistance path. But, alas, the wires to and fro from the radio are teeny weeny tykes so the wire melts.
Bilges are not 3A fuses and sometimes they're on slow trip breakers on larger boats.
I remember a bloke not even putting fuses in bilges for some reason or another.
PS the radio is probably still okky dokky but needs a new wire.
PPS or it could be that the outer plastic covering on the aerial coax has a bare spot to expose the shield and rubs up against the positive bus somewhere. But that doesn't sound near as impressive
PPPS There's a lot of flaws in the first theory. What are they?

Are you suggesting that there is flaws in your first theory, or someone elses. If yours, then not being familiar with the radio I would suggest that the short through the case is not possible due to it being plastic. However, having worked on radio's with plastic cases before, often they have a steel chassis inside, and can be shorted with mounting screws etc. Also does that radio have an earth screw or post or any other connections beside aerial and power?

[finga]

Are you suggesting that there is flaws in your first theory, or someone elses. If yours, then not being familiar with the radio I would suggest that the short through the case is not possible due to it being plastic. However, having worked on radio's with plastic cases before, often they have a steel chassis inside, and can be shorted with mounting screws etc. Also does that radio have an earth screw or post or any other connections beside aerial and power?

Yep, definitely flaws in the my 1st theory.
Goodo on the case. It's more then likely cast alloy by the looks which is backed up by my reckoning that she's a GME GX-300.