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-   -   My Adire ADA1200 has got a problem (http://www.diyaudio.com/forums/class-d/72305-my-adire-ada1200-has-got-problem.html)

BassAwdyO 21st January 2006 08:28 PM

My Adire ADA1200 has got a problem
 
Experts I NEED your help here

I bought an ada1200 from adire about 2 months ago. When I recieved it and hooked it up flipped the switch and nothing happened, the light didnt even flicker, no noises, nothing.

Well I figured the simplest explination, the fuse was blown. Finding the fuse was a task, but when I did, sure enough the filament was vaporized.

Well it just so happens that adire like to use parts on their products that are extremely difficult to find, such as 20x5mm 125v 10amp fuses. So I request for them to send me some replacement fuses(which took at least a month and a half).

In the mean time I go up to radioshack and see what they have similar and the best I can find is a 6.3amp fuse. Well those didnt work exactly. When the amp powered up it blew a fuse. The light did flicker though, so I popped in another fuse. Flipped the switch and it turned on.

The amp worked once it had been powered on. But after letting it sit for a while it blew more fuses upon powerup. I figured this was because I was using 6.3 amp fuses, BUT when I finally got the 10amp fuses from adire the SAME thing happened.

Now If you ask me I'd figure something is faulty in the power supply, but not knowing much about amps I have no idea what would cause this. Its a strange symptom to me because it only blows fuses upon powerup and not under operation.

I'll probably just end up sending it back to adire, but I dont feel like paying shipping again, and I dont feel like waiting indefinately.

If anyone has a thought on what it could be I'd much appreciate it

SSassen 21st January 2006 09:28 PM

Does it use a switch mode power supply (ie. no big torodial transformer is visible)? If not the inrush current from the big transformer is what's tripping these fuses. Any transformer >600VA needs a form of softstart to limit the inrush current, that part of the amp could be malfunctioning. If you're unsure what type of power supply is used a picture would be helpful.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

BassAwdyO 21st January 2006 11:50 PM

its got a BIG torodial transformer.

classd4sure 22nd January 2006 10:05 PM

Hi,

It's caused by two things.

The core of the toroid has excellent memory and so if the current at turn on is out phase with the current at prior turn off the core is essentially saturated and heavy currents can flow as it looks like a short. Rule of thumb is it's not a concern until greater than 300VA, yours would be well over that, probably being a 1 200VA.

Now the other issue is the cap bank in the power supply. At first turn on they'll be empty and pose a heavy load, if the core appears saturated on top of that depending on the phase of the currents as I mentioned it will exacerbate the issue.

This is very commonly referred to as inrush current. The more powerful the supply, bigger transformer, more capacitance, the worse it is. The cure for it is commonly known as a soft start circuit, which limits inrush current at power up. You can both see and test this theory for yourself by making a power cord with a 100W lightbulb in series.

When you turn it on the high inrush current will cause the light to glow brightly for a second(which limits the inrush current as it does so), as the core resets if it has to and the caps charge up the current draw is reduced and the light will go dim again. Odds are the light will only glow when the caps are discharged after a few minutes of being turned off.

The reason you got it to work by sacrificing a fuse is because that initial rush that blew the fuse would have charged the caps somewhat, so they'd present less of a load. If you then change the fuse fast enough before the charge can bleed down again, you stand some chance at having it power up without blowing another fuse.

By leaving it turned off a few minutes the caps will drain through bleeders or the amplifiers biasing circuitry etc. So the next time you go to turn it on that high inrush is back again and your fuse blows.

It seems Adire failed to mention this requirement in their manual, they probably should have included the soft start circuitry themselves, but since they didn't, you'll have to find your own soft start solution, or make one.

Regards,
Chris

BassAwdyO 23rd January 2006 01:26 AM

so you believe they didnt include softstart in the amp altogether and that mine isnt just malfunctioning? I would really think they'd design a better amp than that.

classd4sure 23rd January 2006 01:48 AM

Based on the information you've given .... yeah.

Is there any delay from when you turn it on to when the fuse blows? Do you hear a relay trip right before it blows after that delay? That'd maybe be indicative of a failed soft start circuit. Say a power resistor that failed open, when the relay trips to bypass it a short time after turning it on inrush still occurs just like if you didn't have a soft start circuit.

Why don't you contact them with your new found knowledge and see what they have to say about it. Really, they should have mentioned the requirement for it in their manual if they did not include it.

Regards,
Chris

BassAwdyO 3rd February 2006 09:16 PM

just got an email from adire

Quote:

There isnít a soft-start circuit in the amp; we havenít had a problem with fuses popping unless the line voltage is pretty high. Use of a 15A fuse is perfectly fine, and will eliminate the fuses popping (the components used for power Ė the IEC and the power switch Ė are fine for 15A continuous).
They definately should RE-write the manual

classd4sure 3rd February 2006 09:48 PM

Errrrrmmm..... well you know what the problem is now at least. I'm not so sure their advice is the greatest however.

Inrush surge currents can more than surpass 15 amps ... dorks. They should have at least recommended a SLOW BLOW. Inrush can even trip a 15amp breaker if it's not delayed action.

How much variation do they expect on mains voltage? Very strange thing to say. I'd be tempted to give it right back to them, but you may now make your own educated decision.

Regards,
Chris

BassAwdyO 4th February 2006 12:07 AM

Is there any way to create a softstart outside of the amp? Just something that limits the current draw? 15amp fuses sized 20mmx5mm seem to be impossible to find also...


probably the easiest thing would be getting permission from them to change the power imput plug/fuse holder to a power imput/breaker. That way I can just flip the breaker twice to turn it on and no worries about softstart, or blowing fuses. If a breaker trips, you just gotta reset and flip it on again, much better than fuses!

classd4sure 4th February 2006 12:12 AM

Quote:

Originally posted by BassAwdyO
Is there any way to create a softstart outside of the amp? Just something that limits the current draw? 15amp fuses sized 20mmx5mm seem to be impossible to find also...


probably the easiest thing would be getting permission from them to change the power imput plug/fuse holder to a power imput/breaker. That way I can just flip the breaker twice to turn it on and no worries about softstart, or blowing fuses. If a breaker trips, you just gotta reset and flip it on again, much better than fuses!


You forget about walking over to the circuit panel and flipping the breaker there a few times too.

Do some googling for soft start circuit modules you can probably find something that will work.


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