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Thread ID: 66484	2006-02-24 22:00:00	Power Supply to my speakers problem!	kiwimate27 (9833)	Press F1

Post ID	Timestamp	Content	User
433456	2006-02-24 22:00:00	I just moved here from the US and I have a set of JBL Creature II speakers. These ones. www.jbl.com Now the problem is the power. The voltage isnt the issue it is the amps. The power cord going into the speakers has a big black box on it which is for the power. It says. Input: 120VAC 60Hz 82W Output: 18VAC 3.5A So I need a transformer that takes it down from 210 to 120 volts, which is easy to find, but I need one that does it at 3.5A. I have looked at dick smith and I have called jaycar but they said they can only find one at 1A tops. What can I do to solve this problem?	kiwimate27 (9833)
433457	2006-02-24 23:00:00	Use the input rating for working out needs - 82 watts @ 120 is required - ignore the output side of things.	Peter H (220)
433458	2006-02-24 23:24:00	Jaycar's transformer will do the job just fine. It is rated at 120 watts, and you need less than 100. Cheers Billy 8-{) Edit: Just checked my catalogues & DSE do have an appropriate transformer, but Jaycar is cheaper by far.	Billy T (70)
433459	2006-02-25 06:50:00	When you hook in the stepdown transformer, check your jbl power pack for excessive heat. It may be rated at 60Hz only, in which case it could overheat on the NZ 50Hz supply (simplistically nothing to do with voltage or current) - it's the design of the transformer. If it does get too hot, you will have to source a 50hz capable replacement. It could even fail - some transformers have a heat sensitive fuse inbuilt.	wuppo (41)
433460	2006-02-25 07:14:00	Hi Wuppo, don't recall seeing you around for quite some time . If I recall my theory correctly, it is the increased inductive losses from running 50Hz equipment on 60 Hz that is the problem, but I'd be interested in some clarification . It could be that the lower impedance at 50Hz could cause problems of course, maybe allowing the magnetising current to run at an excessively high level . Anyway, on the kind of loads that a speaker system would impose, I don't think the original transformer would be too hard-pressed while running on 50 Hz . It is only rated for approximately 65watts at the full 3 . 5 amps anyway, and I suspect that the speaker system will not load it anywhere near that figure . Cheers Billy 8-{)	Billy T (70)
433461	2006-02-25 07:25:00	Hi Billy, I think it something to do with saturating the core - the higher freq a transformer is designed for, the less iron is needed. So if you put just enough iron in a design for 60hz, there isn't enough for 50hz, and you are likley to saturate the core at 50hz, causing high internal currents and heat.	wuppo (41)
433462	2006-02-25 22:41:00	Yea I tested out two transformers that I already own. One switched off after 5 mins of use and the other stayed on but after a while there was a burning smell. So I need to look for one with the right Hz?	kiwimate27 (9833)
433463	2006-02-25 22:49:00	why bother with step down transformers? just replace the powersupply. 18v AC output is not that hard to get.	tweak'e (69)
433464	2006-02-25 23:05:00	why bother with step down transformers? just replace the powersupply. 18v AC output is not that hard to get. I have looked for that but everyone has told me that it only goes up to 1 amp while I need 3.5 amps.	kiwimate27 (9833)
433465	2006-02-26 02:20:00	Hi Billy, I think it something to do with saturating the core - the higher freq a transformer is designed for, the less iron is needed . So if you put just enough iron in a design for 60hz, there isn't enough for 50hz, and you are likley to saturate the core at 50hz, causing high internal currents and heat . That's been a problem with American gear over the years, even equipment which has a tapped primary transformer so should have taken 50Hz into consideration . The transformers are designed to run hot at 60Hz, so they run very hot at 50 if they are fully loaded . Finding a 230V transformer might not be too hard . I'd take a multimeter and have a look at a few "12V" car battery chargers . :D	Graham L (2)
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