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Old 10th November 2012, 08:59 AM   #21
AndrewT is offline AndrewT  Scotland
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Is this last post telling us you have wired up a 45+45Vac transformer and the output voltage from the PSU is not in the range +-62Vdc to +-68Vdc?

What is your output voltage?
Do you have an amplifier that is allowed to be connected to that PSU voltage. What is the output voltage when the amplifier is drawing quiescent current?

Remember to measure mains voltage at the same time. It can make a big difference.
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Old 10th November 2012, 09:43 AM   #22
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Quote:
Originally Posted by AndrewT View Post
Is this last post telling us you have wired up a 45+45Vac transformer and the output voltage from the PSU is not in the range +-62Vdc to +-68Vdc?

What is your output voltage?
Do you have an amplifier that is allowed to be connected to that PSU voltage. What is the output voltage when the amplifier is drawing quiescent current?

Remember to measure mains voltage at the same time. It can make a big difference.
My mistake, I apologise. I was taking the rms value to be the DC output - I'm grateful that at least one of us is critically evaluating my posts!

I have just re-measured:
Mains 230 VAC
Output 43-0-43 VAC (I see that there is indeed variation here)

So allowing a 1 volt drop across the rectifier and sufficient smoothing caps, that should give me 60-0-60 DC. Is this correct?

Would this be out of limits for the connex board?
Connexelectronic
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Old 10th November 2012, 11:39 AM   #23
AndrewT is offline AndrewT  Scotland
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I got +-58.5Vdc when mains is @ 240Vac.
The transformer is 230:40+40Vac.

I am very surprised that your UK mains is only 230Vac. Is your voltmeter accurate?
I would expect a 43+43Vac transformer to give 7.5% more than I got when the amp was quiescent (200mA bias).

Is your transformer 43+43Vac?
Seems like you have measured a 40+40Vac transformer when open circuit.
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Old 10th November 2012, 12:32 PM   #24
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Quote:
Originally Posted by AndrewT View Post
I got +-58.5Vdc when mains is @ 240Vac.
The transformer is 230:40+40Vac.

I am very surprised that your UK mains is only 230Vac. Is your voltmeter accurate?
I would expect a 43+43Vac transformer to give 7.5% more than I got when the amp was quiescent (200mA bias).

Is your transformer 43+43Vac?
Seems like you have measured a 40+40Vac transformer when open circuit.
The UK went to 230 V 10% a few years back IIRC Mains electricity by country - Wikipedia, the free encyclopedia

But certainly the transformer could drop a little when under load. My voltmeter is not calibrated by the NPL but, as it's a fairly new Maplin generic digital model, it's probably good to a couple of percent each way. It's good enough for me.

As I'm not really making a lot of progress on this front, I've been taking another closer look at the original class D amp that came built into the sub - it appears that the tops of a couple of the capacitors on the output are bulging suspiciously...

The sub was functioning, but after a period (up to an hour) of being on, the volume level would creep up. And up. And up. I wonder if some feedback loop is being compromised?

I'm going to replace the suspicious caps and see what happens.
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Old 10th November 2012, 12:59 PM   #25
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Pompey Monkey View Post
The UK went to 230 V 10% a few years back
But we didn't.

The UK adopted the harmonised voltage for the whole of Europe.

That adopted standard did not require the UK generators to change all their generation equipment, nor were they required to change their generated voltage.
Quote:
The system supply voltage remains centred on 240 V.[33]
from your link

On the supply distribution side all it did was for the generator/distribution companies to widen their tolerance for voltage supply from 226Vac/254Vac to 216Vac/254Vac.

We still run on the same equipment we always had.

Similarly the European generators were not required to change from their nominal 220Vac equipment. They just widened their tolerances to match the agreed "harmonised" standard.

Where it did make a big difference is to the manufacturers of (domestic?) electrical equipment (TVs, radios, motors, vacuum cleaners etc.) for use in Europe. They, the manufacturers, had to ensure their equipment worked safely when supplied with power within that wider range of voltage tolerance. eg, on the underside of an electric kettle you will see a range of power typically 2500 - 3000W
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Last edited by AndrewT; 10th November 2012 at 01:09 PM.
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Old 12th November 2012, 10:48 PM   #26
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Well - I just ordered one of these: HiFi Assembled IRS2092+IRFB23N15D Audio Mono Amplifier Digital Class-D AMP Board | eBay

I think it'll do the job, although I might need a pre-amp to do it justice. If that is the case, I'll build in a notch filter too!
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