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Mains/battery radios
ThePenkethPedan
Posts: 347 Forum Member
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I have a couple of radios, neither of which work with the mains lead plugged in; however, one of them, a Panasonic, works with batteries in place. The other requires a PP5 battery which I'm not sure are still available.
I' m wondering if this is a common occurrence, I.e., radios not operating through the mains lead but working OK with batteries. What is the likely reason and is it something that can be rectified/repaired without too much expense?
I' m wondering if this is a common occurrence, I.e., radios not operating through the mains lead but working OK with batteries. What is the likely reason and is it something that can be rectified/repaired without too much expense?
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newer models will have a smps power supply. like everythng nowadays. if the inverter board fails then needs replacing. spare part unlikely to be available and in any case uneconomic to have repaired.
as said if still working then you can power via the battery terminals. there used to be "battery eliminators" the exact size of a PP3 or whatever .........
if powering in this way, be VERY careful to get voltage polarity right way round or u might destroy the radio part ........
Interesting idea of 'nothing'
EVERY single part can (and does) fail in such a PSU - the transformers go O/C or shorted turns, the rectifiers go S/C (or VERY rarely O/C), and the large capacitor goes S/C or O/C (in pretty well equal percentages).
However, they do tend to be more reliable than switch-mode supplies, which are of course far more complicated.
Most common failure though is the transformer, often with an internal heat fuse failing - either just because it 'felt like it', or more commonly because of excess current consumption (shorted turns in the TX S/C rectifer. S/C capacitor). Usually though it's the transformer itself, that causes it - small mains transformers are far less efficient than large ones, so run a LOT hotter making them prone to failure.
yes if you short cct the stepdown transformer secondary the enamel will start to melt, with some smoke and a nice sweet smell, and possibly a soothing buzzing sound as the laminated core shakes itself to bits ........
You're showing your complete lack of knowledge about anything electrical again
Rectifier failure is a very common occurrence, and has been for many decades - even back before silicon rectifiers the previous 'metal' rectifiers used to commonly fail as well.
I have that radio if your looking for an update & comes complete with rechargeable batteries which is an optional extra in others
it can take an auxillary input as well through a 3.5mm jack............... perfect for iPhone or streaming in the shower
I shall refrain from your tiresome style of name calling, and just say that rectifier diode failure is quite rare in old style power supplies. (smps rectifiers at higher voltage are a different matter). since these devices are in fact built to take large currents,. of course, you might destroy one by shorting the outputs if it has not been correctly rated for the initial surge current.
I doubt the radio being discussed has a copper oxide rectifier. Unless noah took it on the ark ..........
Again, you're simply showing you have no knowledge or experience in such matters - why do you persist in making incorrect posts about matters you know nothing about?.
Ask any service engineer who has done repairs over a few decades, they will tell you what fails and what doesn't. Back in the days before SMPSU's I use to order mains rectifier diodes in 100's because we used so many of them
Even in modern SMPSU's the incoming mains rectifiers still fail just the same, although the secondary Schottky ones fail more often,
maybe there was a 10 ohm resistor to limit initial surge but not enough to save the diodes of course.
later on there was sometimes a voltage regulator with pass tranny & zener, which would current limit.obviously this arrangement makes lots of heat with other problems ..........
small signal and low current diodes are different since they have a tiny junction area to limit capacitance. but old style rec. diodes have a large junction area for low current density and so r far less easily destroyed.
input rec. diodes in smps are lower current higher voltage so come somewhere in between the 2 catagories. semiconductors in smps are obviously extremely vulnerable to transients unless "very generously" rated.
Again, you're showing you know nothing about electronics - they did (and still do) 'spontaneously' fail.
One possible cause is mains spikes, hence the inclusion of 1000pF capacitors in parallel with the diodes in many circuits, plus series resistors to limit surges - but in practice it never seemed to make much difference.
Again, someone with zero experience and no clue about faults and failures
Try talking to anyone with decent servicing experience, rectifier failures were VERY, VERY common (and nothing else had failed - apart from the fuse, and occasionally the current limiter) - somewhat less so now with mostly switch-mode though.
They were for BOTH
Not according to any posts you've made on these forums
None of which have shown any degree of electronics knowledge or understanding?, perhaps you are referring to servicing something else?
How can the truth be offensive?
rectifier diodes in smps at 400 v are different and the junction can be easily wrecked by transients etc in badly designed supplies. i assume from nigels remarks he is talking mainly about sky boxes ......
Does this imaginary S/C somehow vanish afterwards?, because it's only rarely a cause of S/C rectifiers - exceptions would be switch-mode PSU's, where catastrophic failure sometimes takes out part of the bridge.
???????
Why on earth would you assume Sky boxes? - there's never been anything to even hint at Sky boxes - mostly I was referring to old TV's, radios, and record players - nothing switch-mode.
it takes quite a bit of sustained current to actually melt the junction at low voltage. whereas for smaller active area at much higher voltage these are quite easy to wreck.
im surprised to hear anybody is repairing old consumer electroncs. surely this is uneconomic ?