Help required please!

[Angry Koala]

Whilst I'm extremely happy overall with my new car the stereo is really starting to get on my t*ts!

When I bought it the guy said that when he had taken the car out the garage after 6 months the stereo was playing up with interference. I tried it, it worked fine. 400 miles later I had had no problems with it at all (bandwidth expander seemed to work fine and CD player was perfect).

Next morning I switch it on and go deaf with the worst hiss/crackle I've ever heard - I thought maybe it was a loose aerial connection but it was doing the same with CDs (also makes a noise as if scrambling CD's).

Anyway me and Baz took the dash off yesterday to get to the stereo to try to find the cause. Checked the earth which appeared fine, rewired the live feed and insulated it properly as it had previously been poory soldered and taped. Nothing solved it until we disconnected the bandwidth expander and then everything worked perfectly. Thinking that was the problem and I needed to start looking for a new B.E we put everything back in and it worked fine. 2 minutes up the road switch the stereo on and it's all gone wrong again.......

Unit is a double din Panasonic jobbie.

Anyone got any thoughts please cos it's driving me nuts?!?!

[Martin F]

IMO sounds like a problem in the PA stage of the stereo. Suspect you will need to take it out and let a repair guy bench test it.

Or, just a thought is the stock amp still wired in? (under passanger seat)

[Adzy's Straight 6]

Alrite mate, iv gota jap spec with the original double din, and iv got the same problem, my band expander has made no differece, however this wkend im ripping it all out and completely installing a new system so hopefully that ought to solve it, but other that i just put it down to bad wiring.

[Angry Koala]

IMO sounds like a problem in the PA stage of the stereo. Suspect you will need to take it out and let a repair guy bench test it.

Or, just a thought is the stock amp still wired in? (under passanger seat)

I assume it's still wired as the only thing different that's been done to the system as far as I know is to fit the bandwidth expander.

If the stock amp is under the passenger seat though, what the hell are the boxes clamped to the top of the head unit? There's one cream coloured one which is the same width as the unit not as deep and only about 2 cm thick (which we'd assumed was the stock amp) and another smaller brown box on top of that (which we'd assumed may be a suppressor).

[UltraFlynn]

One is the cruise control ECU. (Brown one i think)

[Martin F]

Nope, one is the AC Amplifier (the larger one) and the smaller brown one is the antenna control relay.

[UltraFlynn]

There you go. I show my ignorance again. :)

I'm sure the Cruise ECU is in that region though.

[Martin F]

Nah, it's up behind the dash roughly where the speedo is towards the bulk head.

May be thinking of the active spoiler or ABS ECU which are below the stereo.

[Angry Koala]

Anyway......... lol, where were you going with the stock amp thought Martin?

[Martin F]

If it is still connected then maybe it's that, which is faulty rather than the head unit. If so you should be able to try or buy one from somebody else. Alternatively take it out of the loop for a while.

Process of elimination, etc.:)

[Angry Koala]

If it is still connected then maybe it's that, which is faulty rather than the head unit. If so you should be able to try or buy one from somebody else. Alternatively take it out of the loop for a while.

Process of elimination, etc.:)

Do I need to remove the seat to get to it?

[Martin F]

Ideally yes, otherwise you will be struggling to remove it. Taking the seat out is easy 5 bolts only.

[Angry Koala]

Ok, so now the seat's been out 3 times and the dash has been off 5 times in order to try to sort it and I'm still no closer to solving the problem. I've checked all the connections and tried taking individual speakers out of the loop in case 1 bad earth is causing the problem. I've had the amp out of the loop completely. If the unit is left on for 5 miutes or more the hiss disappears but the sound quality is really quiet and crap.

Any ideas before I have to go with the assumption it's the unit itself and go about finding the money for a new one? I don't really want to do this and find there's still the same problem......

[Martin F]

Sounds like you've narrowed it down to the head unit :(

May just try one last thing, a seperate earth wire from the head unit to a good clean earth somewhere. Just rig it up to test to see if it has any effect.

[Angry Koala]

unit actually already has an earth running straight to the bodywork underneath it. so I guess that's the head unit then! lol

[Martin F]

Yep, anyway you can borrow one from somebody to double check before splashing the cash.

[Cass]

Some car frames are pos earthed and some neg earthed sounds like yours is pos.

This is a commen drama with stereos and amps.You need a sound supressor which conects to the rca cables from the amp.

This part only costs around £15 and gets rid of that nasty hiss.

I actualy have one in the shed in a box somewhere i can dig it out and post it to you or bring it to the Aug meet if you like

Cass.

[Martin F]

Some car frames are pos earthed and some neg earthed sounds like yours is pos.


Errrrr i'm not aware of any cars after about 1969 that have a positive earth chassis :confused:

[Cass]

My old Fiat tipo and my Hyundia coupe were.

[Martin F]

Are you 100% sure? Positive earthed cars had one major plus in that they hardly rusted at all, and every Fiat I ever see always has a fair amount of rust on it. (or plastic nowadays).

The Supra defenitely is negative earthed, if you want to double check just try (enter disclaimer here) connecting a wire from the positive terminal of the battery to your engine block :D

[Cass]

I had a few pos cars in when i worked with ice installs in Germany aswell.

I think ill pass on the offer of conecting my pos to the block thank you :D

But a sound Supressor is needed for the hissing sound as its a pos feed from the earthing of the amp.

[Cass]

Ive found the part for you its a 15 amp Noise Suppressor Isolation Transformer.

[Angry Koala]

Cass/Martin,

I'm fairly certain the chassis is neg as I get a correct reading on a multimeter if I run it from the positive feed on the stereo to the earth point on the transmission tunnel.......

Also as it was all working fine for the first 2 days of ownership and has since developed the fault I think it's prob the fact that the head unit is as old as the car and it has got a bit temperamental in it's old age.

I've managed to pinch a head unit off a mate so I'll give it a go and see if it fixes the problem. Will let you know how it goes!

Cheers for the help guys - much appreciated.

[Angry Koala]

Ok, the issue WAS the head unit, however, I now have another problem.....

Bought a Blaupunkt single din unit off a mate in work (brand new - won it in a golf comp and doesn't need it as he gets a company car). However, I cannot for the life of me figure out how to install it without having to cut the dash as the hole in the dash is too narrow (side to side). Any ideas anyone?

[Cass]

if it dont fit directly then its a wee job of shaving the dash to fit ,but if i were you id not do that and get one that does fit.

But why listen to a cd when your engine makes lovelys music.:D

[Martin F]

The opening for the stereo on Supras is a little smaller than most trim panels on off the shelf units.

If you don't want to trim the dash panel, then there may be a surround on the stereo that can be removed, or the edges of the stereo may be trimmed. Bit of fiddling around and you should be able to make it look pretty decent.

[Angry Koala]

But why listen to a cd when your engine makes lovelys music.:D

cos it's on a standard exhaust with both cats so the only thing I can ever hear is the BOV lol it's the quietest car I've ever owned!

[Angry Koala]

well there we are. some fun with a junior hacksaw, a stanley knife and a file and one stereo fitted in a newly widened dash aperture. if only I hadn't snapped the damn dash mount off when refitting it I'd have a nice 4 1/2 hr trip to JAE listening to music rather than the panel buzzing the whole way! nice one matt!

[buzz]

mount it in the glove box out the way and bang some gauges in the dash...nice