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Post Time: 10/03/2008 18:09:07 |
sayno_tospam
Total Forum Posts: 6 |
I would like some advice on a curious but very worrying phenomenon and what radiation detection equipment I should hire to rule in or rule out an environmental cause.
In the last couple of months I've had four DAB radios (Revo Pico+) and every unit has died within 48 hours. The problem is the same every time i.e. initially the memory appears to be affected i.e. the radio doesn't hold the last listened to station but re-scans for every available station when switched on. Then the unit will switch on but won't function as a DAB receiver i.e. the screen just remains blank. It is as though the firmware has been totally wiped or the DAB chip has been permanently wrecked. Revo have never seen anything like it or been able to establish just what could have caused such a drastic irreparable malfunction. The fourth unit was kept running in their office for several weeks before despatch to eliminate the possibility of a faulty unit but within 48 hours of being used in my home it too was inoperable. I live in an urban environment in an apartment surrounded by WiFi networks (which surely couldn't wreck a DAB chip?). But maybe there is another radiation source which could do this. Does anyone know?
Thanks
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Post Time: 12/03/2008 22:09:37 |
topazg
Total Forum Posts: 13 |
I have no idea what is causing your problem. Our Roberts DAB radio "tunes" every time it is switched on (even though the power is always applied and the clock is continuously showing the time). The frequency range (220-230 MHz) has little else in it and is unlikely to suffer much interference. Anyway, it is MOST unlikely that normal levels of RF energy will kill it in the way you describe - also, I would expect the computer part to continue working and to display an error message rather than just be blank.
I would suspect a problem with your mains supply - either over-voltage or mains-spikes that the radio is inadequately designed to protect against. Have you measured (or had measured) your rms supply voltage. The EU (and UK) standard is 230 volts, but it is allowed to go up to 252 volts which not all CE equipment is designed to handle properly. We had an serious over-voltage problem in our village in Cambridgeshire (regularly over 250 volts, peaking at 263 on one occasion!) that took almost a year to get sorted out by EdF (the Network Supply Company). That was not "spikey", just too high a regular voltage. If the supply also has switching spikes (from a motor or central heating pump switching on/off or refrigerator pump with failed suppression, etc) then the spikes may easily well exceed 300 volts and get through the internal power supply circuitry and damage the sensitive chips. Has the unit failed when running off the mains, or off the rechargable battery? The battery should actually give it a degree of protection.
Have Revo not identified what failed in any of the units? It is a quality product (at about GBP 130) so I would have thought that after the second failure they would have traced what had failed for their own internal quality control purposes. If it is the main chip, then I would strongly suspect poor design or a duff batch of chips and I would ask them if they self-certified the required EMC tests or if the had a properly approved test lab carry out the required susceptibility tests (these include RFI, spark discharge (ESD) tests and mains noise (spike) tests). Ask them for a copy of their test results. If you are in the UK, then the UK trading standards people are responsible for checking out EMC testing claims by manufacturers. Personally, I think that I would ask for my money back and purchase a different make!
I found the following review by "Fritz" on Amazon.co.uk:
"The Revo really stood out; it was easily the best that I saw on all these counts. I bought one (the first). It was ideal; it picked up about 15-20 radio stations clearly, superb quality sound, looks great (the display is white LED type on black background; none of this headache-inducing neon blue displays), easy to use and neat & tidy. That was in the daytime, with background sounds (cars, people, etc.). At night, quieter, with no background noise the radio seemed a bit loud; in fact it was a distraction. I like the radio to be just heard sometimes, so I can nod off to it. But the volume was on the lowest setting. A volume fault I thought; took it to the shop and compared it to the display model; with all the shopper noise the radio sounded quite low and was the same level as the display model. I decided to keep the radio for all the good points above.
Then my Mum said she wanted a radio for the bathroom. The Revo is ideal; splashproof and with builtin rechargeable batteries (no power sockets in the bathroom). I gave Mum my radio and bought another from the same name shop in Mums home town. Got home and found the tuning control was not turning properly. Swapped it in the original store for my 3rd Revo. To my surprise the volume level could be turned much lower than the 1st radio. So good and lucky result all round.
But, out of the 3 Revo Pico's I bought 2 had faults; plus the volume issue was also apparent on the shop display model (assuming the 3rd radio with the lower volume levels is the correct one).
This is a superb radio, I cant fault it; it is so versatile, yet looks great, sounds superb, works well, is splash proof, portable, small, easy to use, has an external input (e.g. i-Pod, MP3, etc.) and has built in rechargeable batteries (they recharge automaically when the radio is on mains). yet there appears to be a good variation between individual production models. I suggest buying it and if need be change it until you get one with proper volume control - but this could be a pain if bought mailorder (Amazon).
Revo, please, please get the production sorted; you have an absolute winner when everything works as it should. A 5-star radio with 3-star manufacturing!"
So, that doesn't give me much faith in their quality control.
Alasdair Philips (on topaz's computer login)
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Post Time: 12/03/2008 23:30:34 |
sayno_tospam
Total Forum Posts: 6 |
Thanks very much for your response Alisdair
I am going to ask Revo tomorrow if they have any results from two of the dead units sent back to Hong Kong for analysis. The technical team in Scotland could not identify what had lead to the demise of the radios.
I will also check out your other suggestions re: the mains supply. The problem is that each unit (of the four consecutive units) died after running in different rooms off the rechargable battery (whch had been powered for approx 12 hours from one mains socket initially). Also, the units were from different production batches and the fourth unit had been kept running at Revo HQ for several weeks prior to despatch. It was functioning fine until I used it in my home.
When I say the screen goes blank I don't mean that there is nothing to see, but rather it lights up and just displays a series of bars. A kind of error message I suppose, but the unit no longer functions as a receiver. Also, according to Revo they use the same DAB chips as Roberts and Pure so I am a bit reluctant to buy another unit until I establish if there is something in my environment i.e. abnormally high microwave or other fields. I'm no expert on this so don't even know if such a thing is possible. I'm in the centre of a UK city with the potential to be surrounded by all kinds of transmitters legal and illegal. I'm trying to investigate every avenue because I'm baffled by what's happened. Also if there is an unknown field that can mess up DAB Chips what could it be doing to me?
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Post Time: 16/03/2008 21:16:39 |
alasdairP
Total Forum Posts: 173 |
OK, so that's most of my ideas in the bin. It does now sound most likely that high levels of RF energy could be killing it, but then I would expect the same thing to happen to your TV and VHF FM radios.
I suggest that you get the RF levels in your home measured. The cheapest way (for the sort of levels you are looking for) would be to hire a COM Monitor from www.emfields.org - a company related to Powerwatch)
One slight possibility is that you are VERY close to a local DAB transmitter that is grossly overloading and damaging the RF input stage and only affects the DAB receiver as there is nothing much else about at 220-230 MHz and it is a long way from both the 100 MHz FM band and the TV bands (400-800 MHz).
There are lots of local DAB transmitters, some quite powerful, and many are just on top of local buildings (like telephone exchanges). The COM would show if the levels were excessive. Typically, DAB signal levels are in the orders of tens of microvolts to a few millivolts per metre, but very close to the transmitters they can be several volts per metre. RF Power is proportional to V/m squared, so 3 millivolts/metre to 3 V/m (a ratio of 1000-fold) is a power ratio of one million-fold. The inputs should be protected agianst such levels, but it is possible that they are not. We can legally be subject to 28 volts per metre at 200 MHz (ICNIRP Guidelines) but electronic equipment only needs to be tested against failure up to 3 V/m (UK and EU EMC Regulations), so it is possible that being very close to a DAB (or other) transmitter could damage the radio. The COM monitor shows levels using ten LEDs from 0.6 to 6 volts per metre.
Alasdair
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Post Time: 17/03/2008 19:37:08 |
sayno_tospam
Total Forum Posts: 6 |
Thanks for your reply Alasdair
It has now been established that in the dead DAB receivers the memory chip(EPROM chip) has been cleared. Apparently this chip sits on the main board and holds all the operating system. Revo have no idea what could be clearing the memory. They sell thousands of radios and maintain that this fault has only been found in 10 units worldwide - 4 from abroad, 2 from UK and 4 units after 48 hours in my apartment. Revo claim that their DAB radios have all paased EMC testing with flying colours and maintain that the adaptor woild prevent mains spikes. The FM tuner, FM portable and TV do seem to be ok altho' the FM reception is subject to some interference.
I remain concerned that there just might be a transmitter/s? that could be causing this problem and more importantly be a health issue as well. I will do as you suggets and hire the COM monitor but wondered if the Acoustimeter was available yet? |
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Post Time: 19/03/2008 17:53:37 |
alasdairP
Total Forum Posts: 173 |
You are welcome. It is unusual for EPROMS to fail. I suspect they are actually EEPROMS (electrically erasable rather than UV erasable). From my (too) many years (almost 40!) working in the electronics industry (and related fields) I would suspect either (a) Faulty ciruit design around the EEPROM chip (i.e. one or more pins not properly terminated/connected) or (b)a duff batch (or batches) of the devices. There are currently many cheap illegal clones of memory chips floating about the workd, masquarading as top makes, and it is possible that the fabricators (probably in China) bought a duff lot (yes, I know you have had some radio from different batches, but these devices travel around in groups of 100k+ parts). I have repeatedly come across both problems with memory chips. Also, the timing design around the EPROMS and the CPU may be on the edge, and a change in temperature can cause it to go out of spec and the two devices then fail to talk to each other properly.
I now strongly suspect that the problem is not caused by RFI. It is not likely that would cause the EPROM to fail. I would wait until the Acoustimeter becomes available to hire in (hopefully!) 6 to 8 weeks time.
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Post Time: 19/03/2008 18:17:02 |
sayno_tospam
Total Forum Posts: 6 |
Well,that's a relief that the problem is unlkikely to be due to RF as both myself and some of my neighbours were starting to get a bit worried.
Given the length of time surrounding the availability of the acoustimeter I'll probably hire the COM monitor for despatch after the bank holiday if that's ok.
Thanks again |
