Hi,
New member here!
Up to now, I have been using cheap boost converters to get 220V or so, but they are noisy, very noisy.
I gave up on these cheap boost converters, and I've decided to try transformers instead.
I have read a lot about grounding, but something isn't clear to me.
I've always looked at mains earth as a safety connection, which will allow the electricity to be cut if some current flows through the earth wire.
However, I see that circuits use mains earth as the circuit's ground and we can see this from, for eg, the Marshalls. Is this correct?
Possible connections for ground:
1 - Mains earth connects everywhere (doesn't sound right to me)
2 - Mains earth connects to the chassis only for safety, and the circuit ground can be obtained from the middle tap of the PT, if it has one, otherwise from a virtual tap done with 2 resistors.
However, if I connect mains earth to the chassis only, the circuit ground and mains earth are not at the same potential, and some noise should be audible, since all the connectors, switches and pots will be shorting the circuit's ground with mains earth (since they are made of metal).
Can someone help me with this disaster? I want to proceed with the circuit, but I don't want to connect mains earth blindly and power on something which might go boom!
Cheers,
Pedro
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Power transformers and GROUND
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Iain T
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Re: Power transformers and GROUND
It's worth watching some of the general electronics videos on the "Learn Electronics Repair" YouTube channel - this will give an excellent grounding, pun intentional, in how electrical circuits work.
One thing he covered a while back was that all voltages are RELATIVE to some other point. Using a centre-tap and then measuring DC voltage from that may give a different reading from true ground "earth" if they're not referenced together. Looking at something like the Fender Princeton the main centre tap on the power transformers HV output is grounded to chassis to they're the same reference voltage.
From a safety viewpoint though - your chassis should always have a safety earth that connects to your mains ground/earth connection. It's worth understanding the regulations in place around this to get a feel for how important it is. If you don;t do this then your electrical supply safety features cannot protect you - e.g. RCD breakers and fuses external to the amp.
One thing he covered a while back was that all voltages are RELATIVE to some other point. Using a centre-tap and then measuring DC voltage from that may give a different reading from true ground "earth" if they're not referenced together. Looking at something like the Fender Princeton the main centre tap on the power transformers HV output is grounded to chassis to they're the same reference voltage.
From a safety viewpoint though - your chassis should always have a safety earth that connects to your mains ground/earth connection. It's worth understanding the regulations in place around this to get a feel for how important it is. If you don;t do this then your electrical supply safety features cannot protect you - e.g. RCD breakers and fuses external to the amp.
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