Earthing problems? Stereo doesnt work....

[pbrettle]

Chaps / Chapesses,

HELP - I am stuck.....

I decided to replace the rather cruddy Panasonic headunit with a Blaupunkt in the car today. But I failed to get it working. A quick chat with a friend (whos a bit of an electronics wizz) indicated that I seem to be suffering an incomplete Earth connection.

For example, checking the voltage across the earth and 12v power for the stereo I get a reading of about 8.5v - not enough to power it up. The battery is fine and only replaced recently - car starts every time and without any groaning, so its not a bad battery. I think therefore the difference for the voltage of 8.5v means that Earth isnt quite Earth and therefore carrying a small voltage.....

So, where the hell is the earth strap? Got out the Steve Heath book but unclear as to its actual location. I have taken a couple of pictures with the car in bits to help people illustrate where it might be....



This indicates that I have taken off the central console and I expected to find the two straps either side of the gearstick - but cant see anything - though conceed that I didnt remove all of the GRP.



This is a picture of the connector that goes into the back of the old Panasonic headunit (not ISO). I have eliminated the cut wires to be the Earth, Accessory power and Power cables (the blue one which is cut is the ariel power I believe). Note that the red and yellow cables are fused with a 10A fuse - which are fine by the way...

Finally:



What the hell is this...You cant quite make it out, but it says Marconi on it...

Help appreciated on this - currently the Panasonic is back in the car but that no longer works either - I must have disturbed something in the rather crude wiring and hence the drop in power voltage....

Cheers,

Paul



>>> Edited by pbrettle on Saturday 26th July 13:38

>>> Edited by pbrettle on Saturday 26th July 13:38

>>> Edited by pbrettle on Saturday 26th July 13:39

[Ballistic Banana]

In the First picture i would say there should be one under the carpet where that wiring loom is lying across.on the Top of the Transmission tunnel.
Thats where they are on my Griffith. one either side.

BB

Edited to add Pic



>> Edited by Ballistic Banana (moderator) on Saturday 26th July 14:32

[pbrettle]

Ballistic Banana said:

In the First picture i would say there should be one under the carpet where that wiring loom is lying across.on the Top of the Transmission tunnel. Thats where they are on my Griffith. one either side.

Thats what I thought - you recon they should be under the carpet section? There is GRP in an arch shape to make the edges of the little tray there - not sure how to remove them. Still will give it a go....

Anyone else got any ideas?

Cheers

Paul

[Ballistic Banana]

How about runninga direct earth to the Battery earth. is it in the footwell on yours if so it isnt to far to run it.

BB

[bassfiend]

I used to do some off big audio installs in my misspent youth and as a rule even in "normal" cars I will always try to run a dedicated earth and permanent 12v feed for the head unit directly from the battery.

The reason for this is that you are then much less likely to pick up whistles and whines from the cars existing electrical system. I never managed to cure the alternator "whizz" on my old MX-6 to my complete satisfaction but had it been a friends or a customers car then I doubt they would have ever picked up on it as it was very low level.

Before running the dedicated live / earth though it was *FECKING* noisy!!!

Phil

[spend]

Discussed this in:

www.pistonheads.com/gassing/topic.asp?t=48882&f=8&h=0

I now have single earth bolted under dash (above transmission tunnel), not bits screwed through Steering column, rivets.... Seems OK & instruments work a lot better.

Dave.

[andy43]

Bloody 'ell, looks like a bombs gone off in there! Best way I'd say is to run a separate earth cable to the battery, 'cos its only in the footwell, and that black Macaroni box is probably part of the aerial booster system if its linked to the stereo. Pics have certainly put me off changing my pumpin' JVC for something to compete with the exhaust anyway...

[pbrettle]

As suggested I ran a live feed of the battery and the earth from the negative from the battery also. Tested and all works fine. All I need to do now is to swap the stereos over....

One thing though, I did the cabling correctly by visiting my local Halfords. They have specialist cables for direct feeds from the battery for amps and the like, so used these - you know good quality thick shielded cables. Used the correct connectors and they are shielded too.... the daft thing is that my rather amateur electrics are better than those in the car to start with.... little tempted to re-do some of the other electrics - though only a little.....

[tvrtim]

The black box is your Alarm sensor, if you look at it you will see a screw to adjust the sensitivity.

[pbrettle]

Right the continuing woes of my electrics continue. I have cabled up OK and can test the circuits and its good. Re-connected the battery and nothing... nada...zilch. Found that I had blown a fuse which has been replaced and double checked the rest (which are fine).

So how is this possible - the car electrics are fine and everything works, except the stereo. The wiring is correct and the fuse on the back of the stereo is also fine. So why wont it power on? Could I have killed the stereo - but the fuse is OK so I cant of done, right?

Any ideas and suggestions? Anything really cos I am at a loss and am contemplating replacing that old Panasonic back in. Help...

[Ballistic Banana]

Does it have an inline fuse as wellin your live wire, also not sure but do some stereos have fuses actually in the back of them.Are you getting a live feed where it goes in to the stereo, might need to strip a bit of insulation to test it.

Does sound a tad strange, Does the Unit smell like it has been burning at all.

BB

[pbrettle]

BB,

Checked the fuse at the back of the head unit and its fine. No sounds or smells related to burning so assume things OK - and can start the car correctly so electrics not being shorted out for that circuit anyway....

Was thinking while out earlier - would something like a capacitor be useful? Rather than having the full 14v or so from a fully charged battery, regulate it down to 12v - maybe its too much power...?

[Bob the planner]

The alternative is to forget the stereo and just listen to the eight piece under the bonnet

[K4TRV]

pbrettle said:

BB, Was thinking while out earlier - would something like a capacitor be useful? Rather than having the full 14v or so from a fully charged battery, regulate it down to 12v - maybe its too much power...?

Have you actually checked you have a nominal 12v supply going into your stereo? Forget starting the car. If you've all the supplies for the radio and it doesn't work, then substitute the radio for a known working example. Radios are not immune to spikes/undervoltage etc killing them. Oh, and using a capacitor to reduce 14v to 12v?? The radio, or anything else of similar electronic complexity, has/have internal circuits that will usually accept voltages between 10v and 15v. It would take more than just a capacitor to reduce and regulate 14v to 12v.

Trev McM ;-))

[ribol]

Just a thought, we once fitted a head unit that did something similar despite wiring being 100% correct. The problem was the control chip inside had had a fit for no reason and needed to be reset. This was done by pressing a small button down a hole using a pin on the front of the unit(with face off). I have seen reset buttons on other units since, if your unit has one it may be worth a go.

Ivan

[pbrettle]

Thanks - will try the suggestions later. I will put the non-working example into another car which I know works (just in case putting a working headunit into the TVR kills it!). This way I can start to figure out what the hell is going wrong.

Cheers,

Paul

[Ballistic Banana]

ribol said:

Just a thought, we once fitted a head unit that did something similar despite wiring being 100% correct. The problem was the control chip inside had had a fit for no reason and needed to be reset. This was done by pressing a small button down a hole using a pin on the front of the unit(with face off). I have seen reset buttons on other units since, if your unit has one it may be worth a go. Ivan

Made me think , Dont some units have a small screw that also needs taking out before Power up. usual on the top me thinks

BB

[yiw1393]

Right! Informed decision taken on reading the stuff on this thread and have decided not to replace Panasonic thing in dash.

Hope you get it sorted, reckon I know what you're doing this weekend.

[ribol]

yiw1393 said:

Right! Informed decision taken on reading the stuff on this thread and have decided not to replace Panasonic thing in dash.

Coward - get in there and yank some wires out

Ivan

[pbrettle]

Right, found out what the problem was - after taking my car down to CBS in Cambridge (thanks guys). It turns out that the old headunit that was in the car, the standard fit, isnt a 12v one. Its lower, something like 3v or similar. Anyway, there is a diode on the power line which on drain (i.e. plugging it in and turning it on) drops the power to 3v. Therefore no power on!!!

So I wasnt going mad after all. Anyway, cut that out of the circuit and low and behold it worked first time with excellent power. All I need to do now is put all that spagetti back into the dashboard - shame its raining at the moment!

I will post up a picture of the offending component so that all you others in the same boat dont fall for what I did..... TVR's - who'd have 'em...