Radio woe's

Post by **57traveller** » Wed Nov 19, 2003 4:32 pm

Has anyone had any instances of attempts to start a Minor when the battery is flat having an adverse effect on a radio/cd player?
I last used my radio 10 days ago and all was well. Yesterday I fitted the removable facia and there is nothing coming through the speakers in spite of the radio powering up and tuning etc. In the interim I have been experiencing battery problems and having to use the trusty handle for starting on some occasions after trying to use the starter.
I'm wondering if this has done something nasty to my radio/cd. Any ideas?
I've contacted Kenwood but they reckon, yes there is probably a fault and the duff battery is just coincidencal and a bit of a red herring. Seems like too much of a coincidence to me though. Anyone agree?

Post by **MrA.Series** » Wed Nov 19, 2003 5:20 pm

I fitted a period Goodmans Radio, with a mid 70's 40watt 5-band Equaliser and power amp combination unit, running through two 20watt period Pioneer speaker boxes. It was very loud and the sound quality was excellent. One day I started up my mog, turned on the EQ/power amp and the radio, power light on the EQ but not on the radio, nothing worked. The radio wouldn't work on it's own without going thorugh the EQ as a standard radio opperates, and the EQ/power amp doesn't amplifiy any other radio now. Both units are dead without any bangs or burning smells. BTW, positive earth was noted and accounted for.

It's all a mystery why decent radios die overnight in Minors.....

Post by **alainmoran** » Wed Nov 19, 2003 5:31 pm

I'd be suprised if it was the starter handle which killed your radio, but its not impossible.

In terms of theory, the voltage output by your dynamo/alternator is related to the speed at which it turns, so if you wind the handle really quickly (a sharp slam might do it) you might be able to produce a voltage spike which would be enough to kill off the power amps in the CD player.

A good solution to this problem would be to fit a choke to the power leads supplying your delicate kit, this will have the effect of smoothing out the really vicious spikes, and could also improve your sound quality (less noise on the power supply == better sound).

However the condenser/capacitor in your alternator, or the voltage regulator (if you have a dynamo system), should be doing most of this work already. However chokes/filters are cheap and easy to fit, and given your reports I'll certainly be fitting one to my mog before I put my CD-player into it.

Post by **ColinP** » Thu Nov 20, 2003 9:29 am

Just a thought (maybe not a good one),

Is you radio code protected?
If the voltage has dropped to zero (or the battery removed) it's quite likely that the radio will need to be reset....

The other possibility is that as the car started, the radio/amp has a lot of current passed through it (low voltage - high amps). Switch it all off before starting...

Many audio devices have internal fuses as well - you may need to check these! Alternatively, it's possible that just one component has gone - though this isn't easy to check/replace.

Colin

Post by **57traveller** » Thu Nov 20, 2003 5:04 pm

Yes Colin it is coded but this was entered correctly when the facia was fitted. i.e enter code - xxxx - authorised - all working but no output to speakers

I'll be removing the unit anyway and will probably look inside to see if there are any fuses visible but I suspect as Alain that the power amp is probably fried.

Post by **ColinP** » Mon Nov 24, 2003 8:34 am

A funny thing happened this week-end....

After about 1 1/2 hours driving on Saturday (Wiper, headlights, heater, radio -all going), I pulled into a side road, and the wipers stopped working (at the end of their sweep).

Oh, good thinks I, it's the fuse (again). After replacing the fuse a couple of times, the wipers now work (as does everything else on that circuit), but my radio's stopped working!
Sound familiar?

There is a constant supply to the radio (to keep the clock and station memory) which is still working, but the main power to the radio doesn't. And the power take off for the readio is on the other main fuse - not the one that kept blowing.

I'll let you know the investigation outcome - when I can get into it!

Colin

Post by **salty_monk** » Mon Nov 24, 2003 5:44 pm

Some radios do have a small 1 amp or smaller fuse in them which can affect the amplifier circuit only which would explain the lights but no noise.
If you take the radio out & undo the metal casing one part should come off like a lid. The fuse is normally at the back where the power lead enters.
I've also seen some with mini auto style (2 pronged) fuses which are inserted into the back of the unit & are secondary to the inline fuse. Still get to it from the outside though so these are really easy! If you're unlucky then your radio doesn't have this (a lot of them don't) & you've cooked the amplifier chips or the circuit board. If it's the board then some people can go over it for you with a soldering iron which takes ages but works.
In general I would say though that if it's not a fuse then you can only bin it or sell as a non-working item on ebay....
Probably a spike, short, earthing problem that's wrecked it, you didn't try & jump start & get the leads mixed up did you? That'll do it & will take out an alternator too, not sure on the effect with the dynamo though.
Interestingly enough even a short on a speaker lead can cook the amp chips.
One more thought... presumably once you've flashed the dynamo to change over to negative earth the polarity won't just switch back when you start on the handle??

The choke sounds a good idea to me, I'm sure Maplins or RS will do a suitable one...

Wow how longs that post!

Sorry!

Post by **alainmoran** » Mon Nov 24, 2003 6:03 pm

This kind of thing looks good:
http://www.maplin.co.uk/products/module ... Products=3

Although I'm not a qualified electronic engineer, so I may be wrong!

Post by **salty_monk** » Mon Nov 24, 2003 6:32 pm

It looks good.... But I'm no sparky either!

Post by **edd** » Mon Nov 24, 2003 7:07 pm

lthough I'm not a qualified electronic engineer

im not yet but give us another year!

looks ok to me although you could also fit a choke (they clip onto the cable and help cut interferrance ect)

Post by **Willie** » Mon Nov 24, 2003 7:44 pm

SALTY MONK, no, the polarity will not switch back when you
use the starting handle!.

Post by **salty_monk** » Tue Nov 25, 2003 2:13 pm

Ta, haven't gone down that route yet, depends how long the grilfriend can cope without a radio..

as to whether I attempt it or not.

Is it really as easy & hassle free as the techie bit says it is? Does it not cause any side effects or cause problems with any of the old kit that's been used to running positive earth forever........

Post by **alainmoran** » Tue Nov 25, 2003 2:56 pm

Adding a choke is as simple as clipping a 'thing' over the wire, the suppessor will be more complex in that you need to connect it between the wire and the earth.

The choke works by adding an area of magnetic absorbance around the wire.As the current travels along the wire it creates a magnetic field, normally that field passes through air and is fine. When the field tries to pass through the choke, it is absorbed a little, thereby absorbing some of the power from the spike in the wire.

The suppessor works by being an insulator at lower voltages (eg upto 18V in the one I linked to), and then becomes a conductor when a certain voltage limit has been exceeded, thus shorting out the spike. (Once the voltage drops below the limit, it becomes an insulator again, ie stops shorting)

It would be worthwile to fit both a choke and a suppessor, since the choke should damp out current surges, and the suppessor will remove the voltage spikes ... at least it will if I have remembered my physics correctly, but its been a while so...

Post by **Cam** » Tue Nov 25, 2003 4:22 pm

The suppressor capacitor lets AC through, so if it is connected across a DC supply it will earth any AC components (like spike harmonics).

The chokes (inductors) let DC pass through them but block AC. The higher the frequency of the AC signal then the more attenuation (spike harmonics are quite high frequency).

This is why you connect chokes in series with the power supply and suppressor capacitors in parallel with the load.

If you want to improve things even more then connect one choke in the power lead and one in the earth lead. You could also connect two suppressor capacitors: one across the power leads before the chokes and one after.

Post by **57traveller** » Mon Dec 01, 2003 4:31 pm

Didn't use jump leads, only used the handle to start when the battery wouldn't turn the engine. It's -ve earth with alternator anyway, everything else is fine - just the silence!
I will remove the radio/cd unit and check visually - never know might be lucky and find a blown fuse.
Failing that probably out with the plastic.
Replies are appreciated, thanks.

Post by **rayofleamington** » Mon Dec 01, 2003 4:51 pm

and suppressor capacitors in parallel with the load.

isn't it connected from supply volts to ground! Or is that what you meant?

Certainly the only inductors I've worked with needed to be in series, rather than clipped around a wire, but i guess it depends on what you're trying to filter out. To get a strong filter to make a clean line normally you'd need to amplify the field from the current so the feed wire is wrapped into a coil. The easieast way to do it is to wrap it directly round an iron core, then the unit is smaller and very simple.

Post by **alainmoran** » Mon Dec 01, 2003 5:13 pm

The only inductors I have ever used are the ones you find inside your computer (you only get them in 'quality' cases), and these are the clip-on type ... whether they are clip-on or in-series they both rely on the same principle.

Post by **rayofleamington** » Mon Dec 01, 2003 5:34 pm

you only get them in 'quality' cases

lol
the ones i used were 12V versions for an (automotive) electric motor which didn't meet it's spec. They were added as a band-aid due to a low quality product...
But yes they rely on the same principle, and the end result is a reduction in noise and spikes.

I would guess the 12V versions can be bought through specialists or maybe even RS?

Post by **alainmoran** » Mon Dec 01, 2003 5:42 pm

I should think so, although for RS you (used to) need an account, so Maplins or CPC might be an easier source for the majority of us.

Post by **Cam** » Tue Dec 02, 2003 9:10 pm

isn't it connected from supply volts to ground! Or is that what you meant?

Yep, that's what I meant by in parallel with the load.

The inductors that are wrapped around wires are basically using the wire 'coil' as the inductor. The core that the wire is wrapped around serves to concentrate the magnetic flux. Ferrite cores are best for that.