Steve Houghton 1 Posted July 10, 2014 Share Posted July 10, 2014 For those of you who do not receive the news letter from Stan Yeo at Pheonix MP, here is a clip from his latest news letter regarding fuses blowing in transmitters and, it is something I had never thought about. Have you? Recently we have had who a number of customers with blown the fuses in their transmitters. Subsequent discussions have revealed that the transmitters were switched on immediately after being taken off charge. The recommendation is that the Tx battery is allowed a period of time to settle before the Tx is switched on. The reason of course, is the battery terminal voltage, when on charge, is considerably higher than when at rest. Also, the higher the charging current (fast charge) the higher the battery terminal voltage when the Tx battery is taken off charge and the higher the risk of blowing the fuse when the Tx is switched on. If the fuse is blown, before sending the set back for servicing, see if the fuse is situated in the battery compartment as is quite often the case. If so remove the fuse, check the rating and replace with same. If the fuse blows again then return Tx for servicing. Steve A470soaring.blogspot.co.uk Quote Link to comment Share on other sites More sharing options...
Shaunie Posted July 10, 2014 Share Posted July 10, 2014 Hi Steve, I think the important question is what brand? Shaunie. Quote Link to comment Share on other sites More sharing options...
Steve Houghton 1 Posted July 10, 2014 Author Share Posted July 10, 2014 I would have thought this relates to all brands Shaunie. Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 10, 2014 Share Posted July 10, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted July 10, 2014 Share Posted July 10, 2014 The only manufacturer that I know that has a fuse in the main power supply to the transmitter output PCB is JR. And even then I don’t know if this was always so, I can’t remember ever seeing one on the earlier versions, such as the Apex etc. PB Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 10, 2014 Share Posted July 10, 2014 Its a valid warning, with the advent of fast-charging and nimh, an 8-cell pack is no longer "9.6v" and can be over 13v immediately off charge. Worst-case is switching on to 'check the voltage' during a charge - this gives the battery no settling time at all and will momentarily apply the full on-charge voltage to the tx board. Over-volting beyond component specs will damage electronics whether there is a fuse or not. Note that damage is only partially related to failure - damaged electronics can continue to function for years, eventually failing at the worst possible moment! Cheers Phil Edited By Phil Green on 11/07/2014 02:22:37 Quote Link to comment Share on other sites More sharing options...
shirrob Posted July 10, 2014 Share Posted July 10, 2014 my spectrum dx7 has a fuse. have managed to blow it twice before realising that I had been charging it at 2amps ,well above the fuse rating. This because I had to charge it at the field and did not change the programming on my charger from what I use on my flight packs. Very easy to replace though but it does require removing the back of the transmitter and a pc board to gain access cheers Rob Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted July 10, 2014 Share Posted July 10, 2014 Rob, Just out of interest please, does that blown fuse affect the whole transmitter, or just the charging circuit? PB Quote Link to comment Share on other sites More sharing options...
Ronaldo Posted July 11, 2014 Share Posted July 11, 2014 I had this happen on my JR pcm9x Tx. After charging, I switched on, the screen lit up for a brief moment then all went dead. True enough on inspection the fuse had blown. So this doesnt only effect the charging side, but also lost power to the whole Tx. Luckily I had a spare fuse of the same rating, I replaced it and all was fine. After that I now leave it around 15 mins after charging before switching on. No problems since. I have now gone over to Spektrum and still leave for around 15 mins before swiching on. Ronaldo Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted July 12, 2014 Share Posted July 12, 2014 I very much suspect the fuse placing in the DX 7 and the JR are two completely different situations. The JR fuse in the power supply line I cannot understand: - Illogical, Jim, as Mr Spock might have remarked in StarTrek. I’m now convinced the fuse in the Spektrum is in the charging line, close to the battery, it would not generally be possible for the charger to blow a fuse in the power supply line directly. If this fuse is blowing it’s because the charging rate is too high for the fuse current carrying capabilities, but not necessarily of course for the battery’s fast charge ability. This fuse is purely to protect the charging wires connected to the charger in the event of a short circuit appearing within the charger. This can happen, and the battery is easily capable of supplying enough current to make the wires red hot and thus setting the insulation alight. I’ve seen the actual evidence where it’s even happened to a receiver pack; my colleague that actually managed to do this said he couldn’t believe how fast it happened; although this was not charger related. Futaba provided the same protection by providing a diode in the charging circuit, again within the transmitter. Forward biased from the charger making it reversed biased to a short on the wires. I’m fairly persuaded too, that perhaps somewhat more than 95% of fuses are never called upon to actually operate in anger; but it’s the protection devices that are not provided where they should be are the ones that are most important. In my view most batteries, even small lead acids such as those 7Ah flight box sizes should have at least an in-line fuse in it’s own separate charging circuit. As I’ve said before, a mate's house was only saved from fire by virtue of the fact that he had a smoke alarm which called him and he was at home anyway! But a simple fuse would have given complete piece of mind, he’d have been able to leave it in total confidence. This one was indeed totally charger related, unacceptably bad construction combined with poor quality components. … And previously he had frequently left it alone doing it’s thing… However, I do fully appreciate this is certainly not a ‘don’t care’ attitude, but much more of a ‘not aware’ perspective. I’m only a little bit aware of it anyway because I was a little bit involved in it. I can also say that peering inside some of these things, such as the one I’ve quoted above, really is quite nerve racking. Also there has been a number of news reports relating to house fires that have been attributed to the cheap plug-in-wall-socket chargers used for charging gadgets such as phones. Tragically some have resulted in loss of life; in one case 5 people. I’ve always thought the idea of plugging devices directly into the mains is not really a good idea for this reason - When an electrical item is connected via a cable it has a plug, within which can be installed a fuse, usually 3 or 13 amp rated. As an aside, wire fuse types, of which these are examples, have a fusing factor of 2, which means the actual fusing current is 6 or 26 amps. Cartridge fuses vary but are closer rated protection, such as 1.5 or 1.3. Circuit breakers, as I remember, are generally 1, but don’t bank on it. Although I am going back apiece now, modern ones may be much better. When the charger is plugged in the socket it’s now only covered by the fuse or CB covering the ring main, which is a substantially higher rated fusing current. Fusing a low voltage output to cover a high voltage input is difficult, 1 amp at 230 volts is 230 watts. To generate the same 230 watts on a 5 volt output we need 230/5 = 46 amps. Thus to my mind these devices are, to all intents and purposes, unfused. I don’t have a mobile phone, but if I did I would plug it into a multi-way adaptor with it’s built in fuse and fuse it at 1 amp. These 1 amps are also not quite so easy to source, but a Google might do it, such as Amazon. I believe I have seen somewhere, though, one of these chargers with it’s own on board fuse holder provided. West End of the market, no doubt. I have made my own too; years back I bought a MPX multi output constant current mains driven charger, the outputs were superb, but the mains half was probably to some Far Eastern spec I guess, it appeared to be very flimsy, it has a mains lead and plug top but the lead resembled a piece of slightly grown up Futaba battery harness wire! I found a piece of lightweight multi strand cable and and I soldered just one whisker of this across a blown fuse. I was hoping that this might have been less than an amp. But at least I never ever worried about walking off and leaving it running, which was most of the time. Needless to say, though, it never did give me any hassle… Another lengthy post, plenty of talking but not much speaking might be one way of putting it… … and perhaps only just started on the subject… Hoping some of it may be of some interest, though. PB Edited By Peter Beeney on 12/07/2014 23:02:14 Quote Link to comment Share on other sites More sharing options...
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