Eneloops went negative

over-discharge

driven into reverse charge by the better cells

Not unusual

Ok, that means the Radio is at fault then, hence the odd faint drumming noise it makes when it is 'off'.

Time to visit JL or similar for a replacement radio that runs on mains (as this one did until I dropped it while doing some outside DIY and it landed on a corner whereby the impact broke the internal mains transformer away from the circuit board).

The issue is common and is why some batteries die. When batteries go down, some will discharge faster than others. This means that in effect if the device is capable of running on a lower voltage. all the current supplied by the still good batteries will go through the discharged ones, backwards, in effect reverse charging them. Depending on the technology of the battery, it will either ruin them, or just hasten their final demise. Sadly I've never found an answer to this series battery dilemma and I tend to try to batch test them and move all the ones that discharge first into some device with low current needs, and try to pair up matching ones. Its a pain but part of life these days. This is also why I hate chargers that charge batteries in series as well, since this cooks some batteries while the others are still charging. Many portable phones etc, do this for cheapness and I'm always finding them clapped out and hot. Brian

Well that sounds like a bit of a give away. I would imagine any diyer who can solder might be able to repair it with some wire and a bit of araldite. I used to do this a lot when I was younger. The other fault you get is that the little silly connector if it uses a wall wart, damages the socket on the pcb resulting in it not working on battery or mains! Trying to source the exact connector and fixing the broken foil is a nightmare. The radio is not at fault from the battery standpoint of course, this will happen on any load as batteries age at different rates. Brian

No idea what the drumming sound is, a spider trying to attract a mate perhaps? Brian

Brian

I did take it apart to assess the damage, but I think that the impact shattered the outer container of the transformer when it was wrenched off the pcb, breaking the fine wires that are part of the primary winding.

Too much fiddly damage to repair (for me) so I just reverted to Operation Mode B - rechargeable batteries.

Shame, it has a nice sound, not tinny at all with a tone control rotary button too.

Sony do a DAB/FM job that was £69 before Christmas, but now J-L want £99 for it. The Roberts Stream 94i radio has gone up from £168 to £199 too.

Andrew

It was a set of four that have had similar usage.

so what? some are always better than others

Might it be the LF instability that used to be commonly called motor-boating?

...caused by a bad cap.

NT

You have a device which has easily accessible DC power inputs, and is capable of handing a wide range of DC inputs (4 to 6v). This is the same range of voltage that 90% of mobile chargers spit out. USB chargers spit out 5V and your average Nokia/Sony Ericsson proprietary charger spits out somewhere betweeen 4.5 and 5.7v.

Either find an old charger, a mains USB charger+a 2 or 3m USB cable cut off the old phone end connector, verify the polarity and solder the wires onto the battery terminals. Cut a notch in the battery cover to let the wire in - done.

If you want to get clever, either make 2 dummy batteries out of 10mm dowelling and terminate the wires to screws, mark the + and - terminals. or cleaner still - buy a 2.1mm panel mounting dc barrel connector and matching cable connector. Open the radio, connect the tip of the connector to the radio and battery +ve terminal, connect the sleeve terminal to the radio -ve wire, and the switch terminal to the battery

-ve. Verify that inserting the (dead) plug into the socket turns the radio off when running off batteries, then wire the plug to the charger, and mount the socket in a freshly drilled hole in the case.

For the record - I've had a Sony Ericsson CST-60 charger powering an Ikea Molgan PIR light (3xAAA) glued on top as a landing nightlight for years...

Elves inside trying to get out.

In any set of four there is always a weakest cell. The first one to fail will have current flowing through it driven by the remaining good ones. Leakage is often a problem if the cell is abused in this way for long.

Devices that will tolerate a wide range of input voltages tend to cause this sort of problem most often. Many higher current devices have an absolute minimum voltage where they will work and shut down gracefully to avoid driving any weaker cells into reverse bias. LCD based kit tends to self limit when you can no longer read the display on it.