TV Signal Booster - Negative DC12v???

**dsp26** · 30-12-2007 01:15 PM

Hi all,

Was just wanting to know if people can shed some light... I bought a TV Signal Booster for my car TV obviously so i can watch TV while waiting for the mrs.. anyways... my questions are:

1) Why would it require DC-12v (-ve)??
2) Are others setup like this?
3) Is there a way I can invert it to DC+12v (+ve) with a seperate in-line circuit for the power lines?
4) Or is there a kit available in the market that i can build to combat this?
5) Can I simply replace the PNP transistors inside to similar NPN??

At this stage from my limited experience and checking out the components and circuitry, QUESTION 5 seems unlikely but am just making sure.

This is sort of a complex question guys so please no telling me to "reverse the polarity" coz it's no-where near the same thing... only want advice from persons who actually work in electronics. Even someone who repairs amplifiers or car audio repairs would be of big help.

**dsp26** · 31-12-2007 12:39 AM

solved for now... will post modification required after prolonged testing

**IZY-10** · 04-01-2008 10:00 AM

Originally Posted by dsp26

solved for now... will post modification required after prolonged testing

was it because it requires dual supply? If so how did you overcome it?

**dsp26** · 04-01-2008 12:03 PM

^^I don't actually know since the original plug was a ciggy lighter plug which i'm pretty sure is +12v right???

This booster looks Chinese.... can any Chinese on here confirm if cars in CHina are -12v??

I have 3 of them so i'm experimenting on 2... 1 of them i simply reversed the transistors... seems to do something but i'm quite confident it will blow.... the other one my dad installed some NPNs that go the same direction as the original plus we reversed a capacitor that was also wired in the opposite polarity.

Now I have some intermediate knowledge of electronic components and assembly and by following the circuit a bit i've tried to understand it but admittedly i'm not sure of the outcome or the consequences of what i've done... the reversing seems to be working where as is before didn't do much...

***EDIT***
if anyone is interested I could take photos of both sides of the board and possibly draw up a schematic variant in case people can get it to work themselves and use it for their purpose?

**wynode** · 04-01-2008 12:43 PM

Are 'Chinese cars' positively ground? Maybe that's why it is asking for a -12V DC supply.

Haven't seen the instructions on how to wire it up but is there any reason you can't reverse the polarity given you get +12VDC from a normal car and -12VDC via the chasis/ground ?

**dsp26** · 04-01-2008 01:58 PM

^^^not sure unless others can confirm??

I'm pretty sure it's not a matter of simply reversing polarity as I have seen some inverter kits around for like $30...

The way i understand AC is that it's an electrical current that waves on a positive/negative scale... converting this to DC required something like a regulated 4-way diode circuit that suppressed the negative wave... therefore I would have thought -12v would be the complete opposite and not a simple matter of reversing polarity?

**wynode** · 04-01-2008 03:30 PM

Ok now you're talking AC whereas nothing in the above posts had any reference to AC.

Can you clarify what you have an what you're trying to do?

- What (power) input does the booster have? Ie AC or DC and what voltage and frequency range.
- You mentioned an inverter.........where does this come into play? This makes me think you have a Booster that only accepts AC.

I was under the impression that you had a DC supplied signal booster.

**dsp26** · 04-01-2008 05:14 PM

lol i'll start again...

Signal Booster runs off -ve DC.. I was referring to AC only because I was trying to explain my understanding on how DC works and why i believe it to be not a polarity issue.

The inverter.. I came across this inverter kit at Dick Smith 2 weeks ago when I was looking for components to make myself the 14v-->10v regulator for my rearview camera... The inverter however has AC input with a selectable +ve DC12v or -ve DC12v output...

Originally Posted by wynode

Ok now you're talking AC whereas nothing in the above posts had any reference to AC.

Can you clarify what you have an what you're trying to do?

- What (power) input does the booster have? Ie AC or DC and what voltage and frequency range.
- You mentioned an inverter.........where does this come into play? This makes me think you have a Booster that only accepts AC.

I was under the impression that you had a DC supplied signal booster.

**dsp26** · 04-01-2008 05:19 PM

Originally Posted by claymore

Ahh maybe a printing error in translation??? Have you seen some of the posts about translating menu items and things. If you have a few and they are cheap just use it as normal and disregard the diagram. And the cars in china are grounded the same way as cars in any other country not reverse +and -

If I take pics of the limited instructions/specs (like 1 A5 page worth) could someone please translate it for me??

I was hoping it was a print error which is what i advised my dad.. upon installing it, indicator light is ON when switch is off and vice versa so i thought it was a polarity issue.. reversed the hardwiring and still no signal boost or even a flicker on the screen duriong transition or during channel tuning in either off/on mode...

It wasn't until the transistors were swapped around that it somewhat gave a visible signal.. however it was still only turning on while off.

Now I know what i've done may not have even been correct so was wondering if anyone here could confirm or possibly provide a simple inverter circuit of sorts that i could assemble?

Ultimately I don't want to burn my brand spanking new bluetooth/tv/dvd deck... but my dad is adamant it's fine.. just don't want him burning the double-din tv/dvd deck i got them for xmas either...

**dsp26** · 04-01-2008 05:27 PM

this is the instruction/spec on the back of the pack:

**wynode** · 04-01-2008 11:13 PM

Originally Posted by dsp26

The inverter however has AC input with a selectable +ve DC12v or -ve DC12v output...

Inverter converts DC to AC. Ie the input is DC and the output is AC.

Given the signal booster is DC ....... I still don't know why you are talking about an inverter

Post up a schematic and we might be able to help. Otherwise it's possible that the instructions are wrong or the unit is faulty. With DC if it doesn't work.....and you reverse the polarity.....it'll either work or not work at all. With AC it is a different story.....you should not mix up your active and neutral.

**Audio Express** · 05-01-2008 08:59 AM

Originally Posted by claymore

Ahh maybe a printing error in translation??? Have you seen some of the posts about translating menu items and things. If you have a few and they are cheap just use it as normal and disregard the diagram. And the cars in china are grounded the same way as cars in any other country not reverse +and -

exactly! there is no such thing in a car as -12v . in regular electronics - yes.