In an effort to put together my first hi-fi stereo system I bought what was advertised as an Aleph J off an individual through Craigslist. I finally got the rest of my components and am starting to play some music through it. I had to fix the switch, which after soldering the correct wires in the correct places works properly. However, I am concerned about two things: 1) I get a static electricity shock when I touch the amp and 2) there does not seem to be a fuse.
I'd like to not get shocked when touching my amp. I'm new to music amps and it kinda freaks me out. So, I think that it is because the amp is not properly grounded. Any thoughts/suggestions/fixes?
I think it would be safer to operate the amp with a fuse. What power/strength should I get?
Thanks,
Bill
I'd like to not get shocked when touching my amp. I'm new to music amps and it kinda freaks me out. So, I think that it is because the amp is not properly grounded. Any thoughts/suggestions/fixes?
I think it would be safer to operate the amp with a fuse. What power/strength should I get?
Thanks,
Bill
I'd strongly recommend that you pull the amp's plug and don't power it on again until it's chassis is properly connected to earth and fuses are fitted.
U sure the outlet has a proper earth-connection? You can check this with a multimeter, but do it only iff you're really sure how to do this...
A switch is optional, but a fuse is strictly mandatory!
If you search around in the forum you should find the schematic of the Aleoh J somewhere. This amp usually sports a +/-24VDC supply. It's probably similar to the F4's psu. http://www.firstwatt.com/downloads/f4_om.pdf
At firstwatt you can also find the AJ's owner manual.
You can see that there is a fuse before the single-pole switch. The two secondaries are used to make a bipolar supply whose ground is connected to earth via a thermistor (CL60). The chassis is earth-grounded directly.
And please, some pictures would help.
U sure the outlet has a proper earth-connection? You can check this with a multimeter, but do it only iff you're really sure how to do this...
A switch is optional, but a fuse is strictly mandatory!
If you search around in the forum you should find the schematic of the Aleoh J somewhere. This amp usually sports a +/-24VDC supply. It's probably similar to the F4's psu. http://www.firstwatt.com/downloads/f4_om.pdf
At firstwatt you can also find the AJ's owner manual.
You can see that there is a fuse before the single-pole switch. The two secondaries are used to make a bipolar supply whose ground is connected to earth via a thermistor (CL60). The chassis is earth-grounded directly.
And please, some pictures would help.
Upon closer inspection the IEC socket has a built in fuse.
However the only grounding is to the chassis. All grounds meet under the PSU and one wire comes out from under it and is screwed into the chassis. Only two of the prongs on the socket are in use. So, its not grounded to the wall. Should I just run a wire from the chassis ground up to the ground prong on the IEC socket?
Thanks for your help. I know this is pretty elementary stuff, but it was is an Aleph-J so I figured I'd post it here.
However the only grounding is to the chassis. All grounds meet under the PSU and one wire comes out from under it and is screwed into the chassis. Only two of the prongs on the socket are in use. So, its not grounded to the wall. Should I just run a wire from the chassis ground up to the ground prong on the IEC socket?
Thanks for your help. I know this is pretty elementary stuff, but it was is an Aleph-J so I figured I'd post it here.
Okay, I've been out drinking, but I think that your amp is indeed missing a proper earth-ground.
Earth-ground is basically the same as the neutral, but more locally. At the power plant the generators are lifting the electrons to some higher/lower potential, referenced to earth. There are some transformers between your outlet and the plant, but the principle is the same. This reference, neutral, and the wire on the higher potential, hot, come to your house/living room somehow. The earth-wire is your local reference, usually some metal rod prodding into the belly of mother earth. This gives a lower-resistance path for all the unwanted currents (through you or someone else usually) than the neutral lead and thus makes circuit-breakers break faster.
For this reason you should be able to measure the same voltage between neutral/hot as measured between earth/hot. Be very cautious when doing this, if in doubt how to do this, simply don't.
The idea behind an earth-grounded chassis is that loose wires that are at some potentially lethal potential don't put a floated chassis on that lethal potential but instead have a fault current make the fuse pop or engage some other sort of circuit breaker.
Therefore you must connect the chassis-ground directly to the earth-pin of the IEC socket, yes.
People around here usually connect the circuit-ground via a CL60 type thermistor to the (chassis) earth-ground. The CL60 has a resistance of 10R at roomtemp, providing some damping to eventual ground-loop currents. In case of some fault a flowing current would decrease this resistance very fast, providing a low-resistance path. Something similar would be fitting a 10R resistor of several Watts between circuit and earth. But a thermistor (NTC) is nicer.
And don't hesitate to ask basic questions. It's better to be safe than to be room temperature.
And still, pics please!
Earth-ground is basically the same as the neutral, but more locally. At the power plant the generators are lifting the electrons to some higher/lower potential, referenced to earth. There are some transformers between your outlet and the plant, but the principle is the same. This reference, neutral, and the wire on the higher potential, hot, come to your house/living room somehow. The earth-wire is your local reference, usually some metal rod prodding into the belly of mother earth. This gives a lower-resistance path for all the unwanted currents (through you or someone else usually) than the neutral lead and thus makes circuit-breakers break faster.
For this reason you should be able to measure the same voltage between neutral/hot as measured between earth/hot. Be very cautious when doing this, if in doubt how to do this, simply don't.
The idea behind an earth-grounded chassis is that loose wires that are at some potentially lethal potential don't put a floated chassis on that lethal potential but instead have a fault current make the fuse pop or engage some other sort of circuit breaker.
Therefore you must connect the chassis-ground directly to the earth-pin of the IEC socket, yes.
People around here usually connect the circuit-ground via a CL60 type thermistor to the (chassis) earth-ground. The CL60 has a resistance of 10R at roomtemp, providing some damping to eventual ground-loop currents. In case of some fault a flowing current would decrease this resistance very fast, providing a low-resistance path. Something similar would be fitting a 10R resistor of several Watts between circuit and earth. But a thermistor (NTC) is nicer.
And don't hesitate to ask basic questions. It's better to be safe than to be room temperature.
And still, pics please!
I can not find my camera. So I'll have to do my best to describe what I see in the amp.
The IEC receptacle that is being used is here: IEC 320 POWER INLETS
its the 719W-00/04 model I believe.
One of the IEC terminals is hooked up to the transformer. The second terminal is hooked up to a thermistor which is hooked up to one side of the switch. On the other side of the switch is the other set of leads from the transformer. The third terminal, the one that in the PDF of the IEC receptacle is marked with the ground schematic symbol above it is not connected to anything.
So, I'm going to go to my local electronics shop and ask for a CL60 type thermistor and solder it in between the chassis ground and the earth pin, correct?
Thanks for your help and I'm looking forward to logging some more hours listening to my new system.
The IEC receptacle that is being used is here: IEC 320 POWER INLETS
its the 719W-00/04 model I believe.
One of the IEC terminals is hooked up to the transformer. The second terminal is hooked up to a thermistor which is hooked up to one side of the switch. On the other side of the switch is the other set of leads from the transformer. The third terminal, the one that in the PDF of the IEC receptacle is marked with the ground schematic symbol above it is not connected to anything.
So, I'm going to go to my local electronics shop and ask for a CL60 type thermistor and solder it in between the chassis ground and the earth pin, correct?
Thanks for your help and I'm looking forward to logging some more hours listening to my new system.
No, the idea is to have the chassis earthed directly and the circuit's ground earthed via the thermistor.
You should run a wire directly from the socket's earth-pin to the chassis. From there a thermistor to where the circuit-grounds meet.
You could also simply use a wire instead of the thermistor, but then ground loops could build up higher currents potentially resulting in louder hum.
For PSU see http://www.firstwatt.com/downloads/f4_om.pdf page 15 and for ground loops see http://www.passdiy.com/pdf/articles/ground-loops.pdf.
no.
The third pin in your connecting socket must be permanently connected by a direct wire to the chassis. ALWAYS, no exceptions.
The Chassis must be connected to the house Earth system whenever the equipment is plugged into an outlet socket.
Ok, so the local electronics shop only has a CL30 thermistor, and a 6ss60 which I can't find any info on.
So my idea is to first ground the mains to the chassis with a direct wire. Then to replace the thermistor (currently between the mains and the switch) with a wire. Next take the thermistor and put it between the circuit ground and the chassis (or the IEC ground)?
So my idea is to first ground the mains to the chassis with a direct wire. Then to replace the thermistor (currently between the mains and the switch) with a wire. Next take the thermistor and put it between the circuit ground and the chassis (or the IEC ground)?
Yes, that will eliminate the static-shock problem. And I hope by "mains" you refer to the earth-pin of the socket.
No, this thermistor is in place to limit inrush-current. Read the datasheet of the CL60. Maybe also the F1 service manual.
Connect it to the chassis' earth-connection, as this will probably/hopefully be some sort of bolt/washer/nut combination to attach the wires' solder lugs. A properly done bolted connection is very reliable.
All the wiring can be seen in the link in my first reply.
In my house, neutral and earth ground both go directly to ground. Literally, I've checked at the panel, traced the wires: they all go to ground.
Noted. I was wondering how people isolate ground loops away. Thank you for this!
Joe.
THe neutral is supposed to connect to earth ground at the panel. So is the
earth ground that gets distributed through the house (ie. the bare wire in all
the boxes that are connected to the third pin of the outlets).
When you say you're getting a shock - is this a small static tick because it's
winter and you've got a high static environment (ie carpets) ???
If not, unplug that thing and get someone who knows what they're doing
to look it over for you.
Your downside - or rather the downside for every person or pet that has
physical access to this thing - is death, in the case the hot is connected
somehow to the chassis.
You've said that you've figured out the ground pin of the (IEC ??? ) socket
is not connected to the earth ground of the power outlet in the wall because
there is only a 2-prong plug. Get this fixed as a matter of course by
just using a proper 3-conductor power cord. (I think I read before that there
is a 3rd pin on the equipment side that is not being used because it's just
a 2-wire cord ????)
IF then you see that proper grounding results in a blown fuse, you will have
figured out that you're lucky noone is dead because the hot will have been
indeed shown to be connected to the chassis. In this case, just figure out
where the short is, and your problem will be probably forever banished.
Good luck and be careful. You really do have a potential tiger by the tail
here. (little engineer humour there - how do you like that one Nelson????)
(I can see it now----- diyAudio: Our jokes are not like your jokes
bum bum bum bum !!!!!!)
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Little clarification here. What Andrew says is correct.
Where the CL60 is used to "isolate the ground" is as a series element between
the signal ground of your audio circuit and the chassis ground that is
connected to 3rd pin of the IEC socket.
So....
net1 - note all at same potential:
wall outlet ground pin, connects to
ground wire of power cord, connects to
ground pin of equipment IEC socket, connects to (use thick wire - at least 18 ga)
equipment chassis, connects to
pin 1 of CL60
net2 - note all at same potential:
pin 2 of CL60, connects to
signal ground of audio circuit
Since net1 is nominally at ground potential, if there is a short from hot,
a large current will flow and the potential of the chassis will probably rise
to about hot/2 until the fuse/breaker blows and then the chassis will return
to ground potential. You want the thick wire I wrote about so that this wire
can carry enough current long enough that the fuse blows before the wire
melts into separate parts. If the ground wire melts before the fuse blows,
it's open season on all who touch the chassis as it is now at hot potential.
In many parts of the world (UK and Europe, HK, others???) this is 240V and
can, ummm, hurt a bit. Or worse. Even in NA it's pretty nasty at 120V.
You asked for pics...here they are.
This first one shows the IEC socket and the earth pin that is not attached to anything.
This one shows where the circuit is grounded to the chassis.
more!
This first one shows the IEC socket and the earth pin that is not attached to anything.
An externally hosted image should be here but it was not working when we last tested it.
This one shows where the circuit is grounded to the chassis.
An externally hosted image should be here but it was not working when we last tested it.
more!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
You need 2 grounds to make your amp safe:
1. Safety earth. The chassis should be connected to the mains supply earth (that 3rd pin on the IEC). Then you use a 3 core power cord so that the chassis of the amp is actually connected to your household earth (the spike in the ground somewhere outside your house), ie the 3rd pin on the chassis IEC socket is actually connected via the power cord to the 3rd pin on your wall socket.
In the event that you have a short from the live to the chassis, the current will flow to earth through this wire (until the fuse blows). If you do not have this, then the current flows through you and you die.
2. Circuit ground. This is where all the signal grounds within the amp (what you connect to speaker ground) tie together, star ground. It is normal practice to connect this star ground point to the safety ground. In some cases this causes hum. In those cases it is normal to insert either a CL60 between the signal and safety grounds or you can use a pair of diodes wired back to back, with a 10R power resistor and 0.001uF cap in parallel. Either option should stop the hum.
Please don't take chances with this, you are in a potentially
)) life threatening situation here.
Fran
1. Safety earth. The chassis should be connected to the mains supply earth (that 3rd pin on the IEC). Then you use a 3 core power cord so that the chassis of the amp is actually connected to your household earth (the spike in the ground somewhere outside your house), ie the 3rd pin on the chassis IEC socket is actually connected via the power cord to the 3rd pin on your wall socket.
In the event that you have a short from the live to the chassis, the current will flow to earth through this wire (until the fuse blows). If you do not have this, then the current flows through you and you die.
2. Circuit ground. This is where all the signal grounds within the amp (what you connect to speaker ground) tie together, star ground. It is normal practice to connect this star ground point to the safety ground. In some cases this causes hum. In those cases it is normal to insert either a CL60 between the signal and safety grounds or you can use a pair of diodes wired back to back, with a 10R power resistor and 0.001uF cap in parallel. Either option should stop the hum.
Please don't take chances with this, you are in a potentially
)) life threatening situation here.Fran
I suppose the lug in the last picture is where the circuit-ground is connected to the chassis. It seems to be a single screw in a threaded hole of the baseplate.
This is not done properly. You need a bolt that goes through the baseplate, a star-washer and two nuts. As this will also be the point where the chassis meets the earth-wire from the socket, this must be a secure connection that won't go loose.
From Elliott Sound Products - DIY Audio Articles you should read Power Supply Wiring Guidelines and Earthing (Grounding) Your Hi-Fi - Tricks and Techniques.
This is not done properly. You need a bolt that goes through the baseplate, a star-washer and two nuts. As this will also be the point where the chassis meets the earth-wire from the socket, this must be a secure connection that won't go loose.
From Elliott Sound Products - DIY Audio Articles you should read Power Supply Wiring Guidelines and Earthing (Grounding) Your Hi-Fi - Tricks and Techniques.
This is the correct way for the US/NA system. The neutral wires and the ground wires connect together at the main breaker panel (and only at the main panel). All the current travels through the neutral wire, the only time the ground wire carries any current is when something bad happens. Inside your unit the ground wire is connected to the chassis, the neutral wire is NOT connected to the chassis.
Yes, I'd gathered that. Up until the point where I'd learned this, I thought I knew something about electricity. This was several years back, when I decided to DIY a subpanel into the garage for a 220v table saw. I was curious enough that I had to go out and read about how AC electricity works: 3 phase, etc.
It's amazing more people don't burn down their houses, knowing what I know now. For example, I have this receptical in our bathroom with a neutral fault. Who knows how that happened? Nail? Anyway, when I was testing it, it occurred to me that hot and ground made a circuit, and that you can actually run it that way. You shouldn't, but can. "Can" as defined by "it will work," and shouldn't is defined by "that might down your house." As the case may be.
But there have to be people out there who've borrowed a (often uninsulated) ground to make a neutral, don'tcha know.
Joe.
Ok, I have the chassis grounded to the IEC ground. Now, I need to ground the circuit.
I have a 10R 5W resistor here. Can I just put it in between the circuit ground wire and the chassis, or do I have to have the diodes and the capacitor? IE: can I put the just resistor in now and wait for the thermistor to arrive? Or does the circuit require the diodes, capacitor, and resistor?
Thanks for everyone's responses, I'm learning a lot and feeling a lot safer about my venture into DIY hi-fi audio.
I have a 10R 5W resistor here. Can I just put it in between the circuit ground wire and the chassis, or do I have to have the diodes and the capacitor? IE: can I put the just resistor in now and wait for the thermistor to arrive? Or does the circuit require the diodes, capacitor, and resistor?
Thanks for everyone's responses, I'm learning a lot and feeling a lot safer about my venture into DIY hi-fi audio.
Hi Bigbillc,
I would not use the resistor by itself. In fact, if you do not have ground hum with the circuit ground wire direct to the chassis, then you do not really have to do anything else.
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