I read many posts concerning heatsinks temperature (mine run at 45°C, 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 70°C. 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 toroïdal unit from Amplimo.
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 70°C. 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 toroïdal unit from Amplimo.
what's VA consumption of amp and do you have enough air ventilation through case ?
picture or two will be good
picture or two will be good
is that HIFI2000 amp case ?
if yes , then you have enough holes in top/bottom plates
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?
70°C 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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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*15000µF and 8*0.47 ohms. Here is the bridge rectifier: Link.
Hope this helps.
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*15000µF and 8*0.47 ohms. Here is the bridge rectifier: Link.
Hope this helps.
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
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
may i ask a question concerning the "proper mains fuse", i´m 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 it´s 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
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
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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great, tnx!
the transformers are rated 250VA. So i´ll fuse the transfomers with each 1,25A in seperate Fuseholders in the chassis.
This would be after the softstart board i use, when the mains divide to the two transformers.
And i´m still fusing the mains (the one "inbuild" fuse in the plug) for both channels with, say 2A/2,5A slow than?
stefan
the transformers are rated 250VA. So i´ll fuse the transfomers with each 1,25A in seperate Fuseholders in the chassis.
This would be after the softstart board i use, when the mains divide to the two transformers.
And i´m still fusing the mains (the one "inbuild" fuse in the plug) for both channels with, say 2A/2,5A slow than?
stefan
no need for that common fuse ,it'll be redundant
either solder bridge there (if possible on back side of IEC plug ) or put 10A fuse there , to minimize losses
either solder bridge there (if possible on back side of IEC plug ) or put 10A fuse there , to minimize losses
gold fuse 😀 or a piece of rusty nail
tnx for putting some sense in my fusing, calmes me down.
stefan
tnx for putting some sense in my fusing, calmes me down.
stefan
I dont know what wire Amplimo uses in its products but should be similar to this:
Hes Kablo | Products | Enamelled Copper Wire
So, even though the inner temperature is 100 C, it will still work.
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This does not make any sense. For this to be true, the resistor you are measuring across would need to be 0.00047 Ohms. Please clarify. Is the transformer running just one channel? Are you measuring across the resistors on the power supply board? (How many resistors in parallel?) Is it 0.4mV or 0.4 Volt?
Are there just 8 resistors total, or 8 per side? The board I see here: link has room for 8 capacitors and 16 resistors.
Are you using one bridge rectifier, or one per rail?
My mistake.😱
Bias is 0.4V, measured across one of the source resistors (as written on the build guide).
The transformer is powering both channels.
There are 8 resistor total (not counting the bleeder and LED resistors), 4 for the positive rail, 4 for the negative one.
I use one bridge per rail, as on the schematic.
OK, the numbers make more sense to me now. A quick simulation shows the secondary current to be about 6.95A RMS and that puts the transformer at 250VA. It will rum warm and needs lots of ventilation.
Buy a 400VA transformer. Problem solved.
They aren't that expensive in the grand scheme of things. I recent purchased Antek AS-4218 they are very nice and not expensive.
They aren't that expensive in the grand scheme of things. I recent purchased Antek AS-4218 they are very nice and not expensive.
If the DC output from a capacitor input filter is 6.94Adc then the MINIMUM AC rating for the secondary is roughly twice that. i.e. ~14Aac.
This will run the transformer HOT.
For cool running use a secondary AC rating of roughly 4times the continuous DC current draw. This uses the transformer at roughly 50% of it's continuous (capacitor input filter) power.
This will run the transformer HOT.
For cool running use a secondary AC rating of roughly 4times the continuous DC current draw. This uses the transformer at roughly 50% of it's continuous (capacitor input filter) power.
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