| michelevit |
I just received my SI T-AMP and have begun playing with it
last night. I am powering it using alligator clips connected
to a sealed lead acid 7 amp hour battery.
This afternoon I went to my local electrocnics junkyard and found
a 12 volt dc wall wart for 6 dollars. I was happy, but returning
to my desk I plugged it in and found that it actually outputs
15 volts DC!
Is it safe to use on the SI T-AMP? I am having too much fun with
it and hate to pop and blow smoke on me.
Thanks for your reply in advance.
I hope to pull it all apart this weekend and begin fabbing a case for it. |
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| primopyro |
well the wall wart isnt regulated is why...
its 12 volts dc but at how many ampers? lets say its 12vdc 500mah... well when you introduce 500mah of load then the unit will be producing 12volts, until then unloaded its going to be around 15-17vdc
so either grab a regulated one, or introduce its specified output load and your set. |
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| michelevit |
its a 1 amp wall wart.
what kind of resister do i need to indtroduce a 1 amp load?
thanks again for the advice.
mv |
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| Tweeker |
12R. V=I*R. Absolute max voltage listed for the TA2024 is 16V. If you use a resistor across the wart to drop the voltage, your going to be eating up alot of the warts capacity. Also itl get hot, resistor would need to be ~20watts.
It idles at about 70ma so dont expect the SI to drop much voltage when its on. Idealy your transformer would be somewhat more than 1000ma. If you have any a smoothing capacitor or two across the wart will help. Observe polarity.
T-AMP PSU concerns. |
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| BWRX |
| quote: | Originally posted by michelevit
what kind of resister do i need? |
I'd say to use a 15-20ohm 2W minimum resistor to be safe. The T-amp doesn't draw much current at low to moderate listening levels. That shouldn't drop too much voltage unless you really push the amp. |
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| Tweeker |
| Wouldnt a 20ohm resistor dissipate 7 watts or so, or am I missing something? |
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| BWRX |
| The power dissipated in the ressitor is equal to the current squared multiplied by the resistance. At low to moderate levels the amp should only draw up to maybe 300mA average. So, ok. Perhaps the resistor rating should be a bit higher, 5W or above, but you can get away with smaller ones if testing at lower levels. If you try one with too low a power rating and it gets really hot just remove it from the circuit and replace it with a higher power one. |
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| Tweeker |
I see the problem, I was looking at putting a resistor in parallel as a load to drop the rails rather than in series. I think using a 180 ohm resistor as a load in parallel might be a better solution than 15 ohms in series. The 15 ohm resistor would seriously soften the power supply degrading the performance.
The amp draws 70ma at idle, the resistor would draw a tad more, you could test what the rails are with the resistor across them, and they should be that much lower with the amp connected. If it doesnt drop them enough, figure out what load would be needed to drop it from how much it did drop. <14V is fine. |
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| pjburnhill |
Ehm,
I must've used unregulated power supply, since I plugged it in and turned it on and it made noticable humming noise for a while (about 5 mins) and then went silent and the light went off. Now it won't turn back on again.
So, does anyone have any ideas how to get it running again or is it not worth it? Any idea what should I replace? |
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