Step down (240v - 110v) transformer for KingRex T10 amplfier - Page 2 - diyAudio
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Old 10th February 2007, 09:25 PM   #11
luka is offline luka  Slovenia
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Hi

I don't know if this is normal or not, I would say not but I could be wrong. Since you put 110v in, there is no diffrence if it cames from wall socket or transformer. Don't know it that 50Hz instead of 60Hz makes any diffrence either.
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Old 10th February 2007, 10:02 PM   #12
johnm is offline johnm  United Kingdom
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I think it's the 50hz running into a 60hz transformer. It really is too hot to touch and is making the whole chassis very hot. Definately not normal so I've gone back to using my Skynet 8080 SMPS supply, which sounds fantastic with the KingRex so not all bad.

I'll wait for the 240v KingRex PSU in the meantime. If that gets way too hot then it must be a bad design. I'll keep them informed as I'm sort of testing the amps for them and letting them know what I think.

Cheers.
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Old 11th February 2007, 09:24 AM   #13
jtjames is offline jtjames  Taiwan
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I will suggest you use PSU for best sounding. The switching power supply is a bad option. i tryed many other switching type power supply (but not 8080).they use for t20 amp i feel the bass punch is very pool.
In 50hz or 60hz 110ac for psu is no difference,I tryed PSU+T20 AMP+ CD PLAYER in 110v wallsocket ,continue run music over 72hours(the t20 amp volume knob set on 12 o'clock position,it can normally work. the traditional power hot then switching power is normal and OK.(could you tell me how many degree temp on psu ,you sai'd is very hot),mayby you can use volt meter to check your 110v ac(it should be 110v-120v is good).

Sincerely yours

james
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Old 11th February 2007, 11:00 AM   #14
johnm is offline johnm  United Kingdom
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I respectfully disagree with you. The Skynet 8080 SMPS sounds great with the KingRex T20 (sorry I have been writing T10 throughout this thread - whoops!). Mine's putting out 13.3v. The music is very smooth, but never boring. Loads of detail but not artificial in any way - it just sounds natural. Great bass weight, which may be in part due to the Nichicon 20,000uF cap on the output of the SMPS. The amp - with no music! - is dead silent with my ear against the speaker as well which isn't the case with another SMPS power supply (for a PC monitor) I tested. I think the 8080 is a very well designed PSU.

Using my stepdown transformer the torroidal inside the KingRex PSU got so hot you could smell the rubber isolation pads used top and bottom on the transformer - surely not a good sign. The circular metal fixing plate on top of the transformer was scorching hot to touch - not red hot but the heat was travelling through the fixing bolt and into the rest of the chassis. The underside of the chassis was again too hot to touch. This kind of heat is not kind to capacitors and would probably result in those having a far shorter life-span than they should. The transformer also buzzed quite alot as well. If this is normal and it does get hot there should be ventilation slots in the top of the chassis... I like to leave my amps on all the time, which isn't possible or safe when the PSU is this hot. I'd worry about insulation on wires possibly melting or a component failure.

I shall do as you suggest and measure the voltage - perhaps it is too high where I live.

Cheers,

- John
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Old 11th February 2007, 11:40 AM   #15
johnm is offline johnm  United Kingdom
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Update: Just measured the voltages before and after the stepdown transformer. This transformer has a 500va rating by the way.

Before, it's 237v, and after it's 121.3v. This seems slightly high - could this account for the heat being generated?

- John
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Old 11th February 2007, 12:30 PM   #16
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No, what you probably have going on is a fixed loop around your toroid. This means that a loop of conducting material (probably the center bolt, top/bottom plate and casing) will act as a functional extra turn of wire around the toroid and behave like a shortcut at the same time. Advise: remove the center bolt and just attach the toroid with some plastic tie-wraps to the ground plate. Then see what happens. A 500VA trafo should not be under any strain with a TA2020 based amp. See also my own experience with this phenomenon.
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Old 11th February 2007, 01:47 PM   #17
johnm is offline johnm  United Kingdom
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I was using the PSU with the top plate off and still getting this heat. Just had a check and there appears to be no loop in the system that you speak of, and there is plenty of space around the transformer.

Thanks for your link - will take a look at that now.

Cheers,

- John
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Old 11th February 2007, 03:31 PM   #18
jtjames is offline jtjames  Taiwan
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some transformer output side when you serial connect two coil you must consider the coil direction.
could you change the stepdown transformer output line connection and test the temp again.ths
pls see the attach file to change it.(from a to b)


sincerely yours

james
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File Type: jpg a to b.jpg (52.0 KB, 105 views)
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Old 11th February 2007, 03:31 PM   #19
jtjames is offline jtjames  Taiwan
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maybe you try 240 to 120v transformer is best solution,i ask some friend they say in a transformer output side two separated coil can't serial connect,it will cause some problem.because the magnetic field direction will chaos.

Or you can wait more days,she will send another 240v input PSU for test.

sincerely yours


james
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Old 11th February 2007, 08:10 PM   #20
johnm is offline johnm  United Kingdom
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Thanks for your information James - I take it you work for KingRex? Impressed with the amp using the skynet 8080 - from experience I know the chips take a few days to burn in so I'm looking forward to the sound improving over the next few days.

On my step down transformer I currently have the Yellow and Black connected, and the red and orange supplying 121v ac to the Kingrex PSU.

Transformer details are:

Red - 55V / Black - 0V

Yellow - 55V / Orange - 0V

The informatin sheet says it can be connected in series or parallel.

Perhaps I should try joining the Black and Orange as you suggest in diagram B and see if that makes a difference?

Cheers,

- John
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