losing my memory......can you help?

[Matata]

not quite boaty but similar problem.. I have struck with a 2.5 litre diesel. Ive installed a dashboard radio that keeps losing its memory. It needs two feeds. one permanent from the 12v battery and the other from the switch ignition. The permanent 12v live is needed for the radio to work . My problem is when I store a station in the memory and then switch the truck off, the permanent live dips below 9v when I start it on again by the time the glow plugs and starter have done their stuff. Any smart way around it?? Nik

 

[solent clown]

wire one of these in to the memory wire and the stereo earth

https://uk.rs-online.com/web/p/prod...qjnbhVwKAXjb8t9dgIRoCz44QAvD_BwE&gclsrc=aw.ds

 

[solent clown]

this for the holder
https://www.cricklewoodelectronics....n7XA8GlfkQqanAJTkoqrrODrydRY18jBoC2OMQAvD_BwE

 

[Matata]

The "memory wire" is the same wire the radio gets its main feed from. It probably sucks 1/2 amp when in use. So I can't see how one of those batteries would help. surely it wouldn't last very long??? Nik

 

[William_H]

The memory wire is connected to battery full time. It should draw very little current as it is expected to not flatten the battery over many months of being parked. If you connected one of those small batteries to the memory wire it might be OK but you don't know what is happening inside the radio when full power is on. It obviously gets power then.
The solution is using a diode in the memory line cathode (bar) to the radio anode (arrow tail if it has one) to the 12v supply.
You then fit a largish electrolytic capacitor (100 microfarrad 30 or more volt) from radio memory input to ground. The capacitor charges up like a battery when power is on. When the voltage drops too low the capacitor feeds voltage to the memory but the diode stops the capacitor voltage trying to supply the truck electrics.
Note the voltage ratings of capacitor and diode are max. before failure so any rating over the battery voltage should be fine any thing over double the system voltage will give a margin of safety. So cheaper than a small battery and lasts forever. ol'will

 

[solent clown]

The "memory wire" is the same wire the radio gets its main feed from. It probably sucks 1/2 amp when in use. So I can't see how one of those batteries would help. surely it wouldn't last very long??? Nik

it should be a seperate wire, normally yellow

 

[Graham_Wright]

Cracked it! struck = a truck.

Bit slow today.

 

[Matata]

told you I was losing my memory...struck/truck!!! double checked...red ids permanent live 12v.....yellow is 12v thro ignition switch. I like william h's idea....I don't quite /fully understand it though. Can someone clarify it a bit more. I'm ok with a soldering iron and a bit wiring....Ta Nik

 

[solent clown]

iso-wiring-harness-diagram-solutions-car-radio-kenwood-stereo-instructions-yellow-color-coded-wire-red-volt-mory-ignition-tures-blue-black-ground-audio-adapter-adap-codes-code-ine-970x619 by mark punksteel, on Flickr

 

[solent clown]

that is the correct din wiring code for 99.999% of stereos. Please observe function of red and yellow wires

 

[Matata]

Silent clown...your a genius! My truck is 20 yrs old and i took the original stereo out and copied the plugs/wiring/colours as per original. It turns out you were right .Theyve changed/swapped the colours. I swapped the red and yellows and bingo! Many Many thanks. I do like William H's idea though! 2 pints of the "Black stuff" waiting at the bar! Nik ( You guys saved me a load of hassle )

 

[solent clown]

happy days!