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Old 3rd October 2015, 06:20 PM   #1
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Default Transformer temperature

I read many posts concerning heatsinks temperature (mine run at 45C, so no problems here), but what about transformer temperature.
I found that my Aleph J runs pretty hot, not only on the heatsinks but inside the case. When I opened it, I noticed that the transformer was very hot. I measured it at 70C. I didn't manage to measure the temperature of the mounting plate, but I can't leave my finger on it more than two seconds before it hurts.

Is it a normal "behaviour" for a transformer or do I have a problem?

PS: The trafo is a 300VA torodal unit from Amplimo.
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Old 3rd October 2015, 06:39 PM   #2
Zen Mod is online now Zen Mod  Serbia
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what's VA consumption of amp and do you have enough air ventilation through case ?

picture or two will be good
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Old 3rd October 2015, 08:14 PM   #3
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I don't know the consumption of the amp. It's an Aleph J, on Fistwatt's website, announced consumption is 200W.
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Old 3rd October 2015, 08:24 PM   #4
nec3 is offline nec3  Turkey
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70C is not high for a transformer.
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Old 3rd October 2015, 11:32 PM   #5
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Quote:
Originally Posted by folkdeath95 View Post
I don't know the consumption of the amp. It's an Aleph J, on Fistwatt's website, announced consumption is 200W.
is that HIFI2000 amp case ?

if yes , then you have enough holes in top/bottom plates

what Iq you set ?
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Old 4th October 2015, 08:34 AM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by folkdeath95 View Post
...........................PS: The trafo is a 300VA torodal unit from Amplimo.
Quote:
Originally Posted by Zen Mod View Post
what's VA consumption of amp ...............
Quote:
Originally Posted by Zen Mod View Post
i...............what Iq you set ?
tell us more.
What is the AC current rating of your 300VA?
What PSU type have you fitted: Choke input or capacitor input?
What continuous DC current is/are your ClassA amplifier/s drawing?



Quote:
Originally Posted by nec3 View Post
70C is not high for a transformer.
70C for the surface temperature is very hot for a toroid transformer.

Have you any idea how much hotter the primary and the core is?
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Old 4th October 2015, 09:05 AM   #7
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Yes, Zen Mod, it's a Hifi 2000 case.
Bias is set at 0.4mV, so I presume Iq is 0.85A (if I understand correctly what Iq is).

Andrew:
The transformer is an Amplimo 77014 with 2*115Vac primaries connected in series.
PSU is DIYaudio's Universal board, CRC filtering with 8*15000F and 8*0.47 ohms. Here is the bridge rectifier: Link.

Hope this helps.
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Old 4th October 2015, 12:28 PM   #8
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Iq would be twice that , per channel , having two pairs of outputs .

so , dissipation per channel is , assuming 22Vdc rails :

Pdiss=2 x 22Vdc x (2 x 0A85) = 74.8 VA

it means , xformer is tortured with steady 150VA

so , power taken - nothing to worry about

temp - little higher than I would allow it

however , just use it ....... bugger will either survive , or melt .

just take care to have proper mains fuse
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Old 4th October 2015, 02:02 PM   #9
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just take care to have proper mains fuse
may i ask a question concerning the "proper mains fuse", im just making new dual mono PSU for regular FW 22V rails amps (230 V).

My mains fuse at the Plug is 1,25A and its for both channels. When any trouble occurs its most often in ONE channel. So does it make sense to fuse the cables for the two transformers again with EACH the half of the mains fuse?

thanks,
stefan
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Old 4th October 2015, 02:25 PM   #10
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put one fuse per xformer , mounted either inside or on back panel

fuse value - xformer VA rating/mains voltage , then first standard value , slow type

however - when I'm making an amp , be it dual mono or stereo PSU , I'm usually putting just one fuse
when amp is properly done , I'm counting only on xformer melting ...... then even nail as fuse is effective .... enough

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Last edited by Zen Mod; 4th October 2015 at 02:28 PM.
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