while I was doing some tests I discovered that with the amplifier off, but with the power outlet at 220V, I repeat everything off, I find myself having a contact/impulse signal at the crossover wires/at the speaker connector plugs. if I unplug the 220V plug and after 15/20 seconds, time for the capacitors to discharge, the signal disappears. this is serious, there is a current input that shouldn't be there, right?
this Amplifier
this Amplifier
Questions to ask.
1/ Is the amp using a linear power supply or an SMPS?
2/ If linear is there a snubber across the mains switch contacts such that a cap appears in series with the mains supply when off (which is normal on some equipment)
3/ Is OFF really off or is it a Standby function?
And rereading your first post... you might be describing stray pickup from the speaker/speaker wires that might actually seem to have lots of noise/hash/random stuff on them. That is normal if the amp disconnects the speakers via a relay etc as the leads then float and pick up anything going. Even if no relay the amp output could become a high impedance point and allow the same.
1/ Is the amp using a linear power supply or an SMPS?
2/ If linear is there a snubber across the mains switch contacts such that a cap appears in series with the mains supply when off (which is normal on some equipment)
3/ Is OFF really off or is it a Standby function?
And rereading your first post... you might be describing stray pickup from the speaker/speaker wires that might actually seem to have lots of noise/hash/random stuff on them. That is normal if the amp disconnects the speakers via a relay etc as the leads then float and pick up anything going. Even if no relay the amp output could become a high impedance point and allow the same.
you can see how the amp is powered - here > https://www.diyaudio.com/community/threads/carver-m-1-5t-recap-and-rca.424754/
yes, it has the modification with a switch on the rear panel. I repeat once the plug is removed from the 220V current, there are no more contacts... almost as if the button does not close properly.
this?
the power supply emits this buzz that comes right from inside. tried to tighten the screws of the fins and also repainted with a very thick paint, but the buzz remained - this also moves to the speakers, in a light way, you can only hear it from close up and it does not increase with the volume - it is exactly what comes from its power supply. there is a curious detail, when you move the trimmer that regulates the voltage, it stops buzzing, but then comes back.
That is a traditional linear type supply.
I'm not really sure what fault or symptom you are chasing here 🙂
Is it something you hear from the speaker when its 'off', or is it something you see on an oscilloscope when it is 'off' or are you getting a bit of an electrical shock from it?
Hard to say. Buzz from transformers is common and so is slight buzz/hum on the audio output in may amps.
It might help to see the circuit. What voltage does this trimmer adjust? I do know some Carver amps use SCR (thyristor/triac) controlled PSU's and so that in a way makes some kind of sense. If you reduce the the rail voltage (assuming that is what the trimmer does) then the amp will run momentarily on the stored charge in the reservoir caps and the power supply will be idle. When the voltage falls enough the power supply starts up and you hear the buzz again. That is a possible scenario.
@Mooly
let's do one thing at a time, otherwise I'll go crazy. 😊
with the amp off using the button on the back, if I disconnect the wire from a speaker, for example the negative, and disconnect and replace it, I can hear the contact in the speaker cabinet, indicating that the amp is unusually loaded. If I repeat the same thing by removing the plug from the 220V, nothing.
let's do one thing at a time, otherwise I'll go crazy. 😊
with the amp off using the button on the back, if I disconnect the wire from a speaker, for example the negative, and disconnect and replace it, I can hear the contact in the speaker cabinet, indicating that the amp is unusually loaded. If I repeat the same thing by removing the plug from the 220V, nothing.
OK 🙂
Do you mean you hear a 'click' from the speaker? If so then that may be just a tiny residual DC voltage at the speaker terminal. Even a millivolt or two of DC is audible as a click when you connect a speaker across it.
Try measuring the DC voltage across the speaker terminals of the amp before you remake the connection to see if there is a small DC voltage present. You are looking for just a few millivolts.
sure, there is some residual that passes through the button. at the moment, once the plug is removed from the 220V, it completely pops and I assume that the few millivolts disappear too. better that I change that button/switch with something more serious.
If the button is a mains switch then check and see if it has something like this across it. A capacitor like this will allow a small current to flow and that is enough to generate a very small rail voltage in the amp. You may then hear that as a click if you connect/disconnect speakers. The cap is essential to protect the switch and the behaviour is normal.
A faulty mains switch that passed a small current when off would most likely not last long and would burn and carbonise so I don't really think that is the problem.
Again, without seeing a circuit diagram it is hard to say for sure. I suspect the Carver mains switch is actually not disconnect the mains fully by design like in this second image which is a Carver M500T amplifier. This is NOT a normal mains on/off circuit and the unit is still partly powered.
I would doubt you have a fault with this one 🙂
A faulty mains switch that passed a small current when off would most likely not last long and would burn and carbonise so I don't really think that is the problem.
Again, without seeing a circuit diagram it is hard to say for sure. I suspect the Carver mains switch is actually not disconnect the mains fully by design like in this second image which is a Carver M500T amplifier. This is NOT a normal mains on/off circuit and the unit is still partly powered.
I would doubt you have a fault with this one 🙂
I'll change the OS and see if I can find the image of the button wiring because among those you saw it hadn't been mounted yet.
let's see... I'll summarize this Carver M 1.5t, which pushes and sounds divine. this amp was born without a button with the wire directly to the American plug. initially it was placed under a base with a switch, then I saw this modification and implemented it with the button placed on the back near the power cable.
the first pic you see the 220/230V input area, while in the second you see the two cables that go to the button, here now in the fly version because I did a first test always with the switch base ready for any eventuality.
the first pic you see the 220/230V input area, while in the second you see the two cables that go to the button, here now in the fly version because I did a first test always with the switch base ready for any eventuality.
Its not easy to follow tbh 🙂
I suppose the first question has to be did it do all this before it was modified? Also I see what looks like a cut ground wire in the first picture and an intact lead with ground in the second.
I suppose the first question has to be did it do all this before it was modified? Also I see what looks like a cut ground wire in the first picture and an intact lead with ground in the second.
Just out of curiosity, since I'm not a technician and Mooly's experience is at least ten billions times greater than mine, I took a look at the photos you linked describing it as "the conditions of the amplifier as it arrived to me 30 years ago etc. etc." and the following is a detail of one photo
where you can clearly see the cut ground wire inside the thermal glue that seals the power cable that originally has no switch at all.
For this reason I guess that the amplifier has double insulation and does not need a ground connection.
However, if I understood correctly you put a switch on the power cable for your convenience, right?
Is the switch bipolar?
In the sense that both the neutral and the phase are disconnected?
Does the switch have a built-in fuse?
Is the switch for 230VAC?
Rated for how many amps?
What quality?
Is it new or used?
How did you attach it to the amplifier chassis?
Just out of curiosity. 🙂
where you can clearly see the cut ground wire inside the thermal glue that seals the power cable that originally has no switch at all.
For this reason I guess that the amplifier has double insulation and does not need a ground connection.
However, if I understood correctly you put a switch on the power cable for your convenience, right?
Is the switch bipolar?
In the sense that both the neutral and the phase are disconnected?
Does the switch have a built-in fuse?
Is the switch for 230VAC?
Rated for how many amps?
What quality?
Is it new or used?
How did you attach it to the amplifier chassis?
Just out of curiosity. 🙂
it is not connected. the original cable with American plug had only two wires and so it was reconnected.