I'm not sure from the explanations, and please forgive me if I'm stating something very obvious ...
Resistance measurements only to be done with the transformer not connected to anything. Once you connect the transformer to the mains voltage, only try to measure AC voltage ...
And the light bulb in series with the mains connection wired in one of the primary leads, not across the two mains power leads) is a very good tip also. It acts as a current limiter, so prevents the effects of a total short circuit.
Best regards,
Claas
Resistance measurements only to be done with the transformer not connected to anything. Once you connect the transformer to the mains voltage, only try to measure AC voltage ...
And the light bulb in series with the mains connection wired in one of the primary leads, not across the two mains power leads) is a very good tip also. It acts as a current limiter, so prevents the effects of a total short circuit.
Best regards,
Claas
Don't bother about this guys, I have run out of time and patience with this transformer. Another one is on it's way. If I get really bothered I might send the transformer back to Antek to find the problem, otherwise it will probably go in a drawer and eventually to scrap.
While not cheap, these days such an amazing toroidal is remarkably less money that they once were. If it were back in the day when they might have cost a grand or so I'd probably be rewinding it , as I have rewound lots of guitar pickups etc. but no, I have given up on it and will not mess about with the amp any more till the new one arrives.
Thanks so much for your input. I'll come back when it's happening again, hopefully on a more positive note. Cheers.
While not cheap, these days such an amazing toroidal is remarkably less money that they once were. If it were back in the day when they might have cost a grand or so I'd probably be rewinding it , as I have rewound lots of guitar pickups etc. but no, I have given up on it and will not mess about with the amp any more till the new one arrives.
Thanks so much for your input. I'll come back when it's happening again, hopefully on a more positive note. Cheers.
Many years ago I had a few toroids made to order by Harbusch:
toroidal TRANSFORMERS-
I suppose it is worth asking for a quote, you can specify a 500VA toroid but ask for a next size up iron (600VA ??). This will prevent any buzzing from developing later on.
toroidal TRANSFORMERS-
I suppose it is worth asking for a quote, you can specify a 500VA toroid but ask for a next size up iron (600VA ??). This will prevent any buzzing from developing later on.
I have a few admissions to make regarding the transformer problem. This may explain how I could have destroyed a robust thing like the Antek4218.
OK when first switched on there were a few things wrong with my power supply.
I had not seen a schematic so did not understand how the polarity of the LED's should go and I don't know exactly which way they were but let's assume that one was correct and the other was wrong since I arranged them in mirror pattern.
Then I had much too small a resistor on each LED so they were bound to blow anyway.
Then I had way too small a bleeder resistor and one actually got hot enough to start to brown before going open circuit.
After the initial failure I was measuring the AC at each bridge and it was reading minus18volts. Being ignorant even of my multimeter I didn't realize this was because I had my test leads reversed. Instead of working that out I took the leads off the DC terminals of the bridge and swapped them over onto the power boards.
However at that point the caps discharged with a big spark which was sent back into the recs and the transformer. I'd say this is what fried something internally in there.
Sorry I was afraid to mention this before but I realize that this is yet another learning curve for the rank beginner such as myself and I apologize for using some of your brainpower when you didn't have all the information.
I can only justify this behaviour in one way. That is after building this amazing thing and taking lots of very careful time about it I got to a ridiculous state of excitement and had to go at it like a bull at a gate that night. I already knew I should have just left it after the first attempt , asked lots of questions and I probably would have sorted it without causing all this damage. But I didn't so now I pay the price. At least I didn't get zapped by those caps going off.
So hopefully this is the last time I have to learn this lesson . Really apologize for not being totally up front with you guys. You are so helpful. Please forgive me.
Cheers.
OK when first switched on there were a few things wrong with my power supply.
I had not seen a schematic so did not understand how the polarity of the LED's should go and I don't know exactly which way they were but let's assume that one was correct and the other was wrong since I arranged them in mirror pattern.
Then I had much too small a resistor on each LED so they were bound to blow anyway.
Then I had way too small a bleeder resistor and one actually got hot enough to start to brown before going open circuit.
After the initial failure I was measuring the AC at each bridge and it was reading minus18volts. Being ignorant even of my multimeter I didn't realize this was because I had my test leads reversed. Instead of working that out I took the leads off the DC terminals of the bridge and swapped them over onto the power boards.
However at that point the caps discharged with a big spark which was sent back into the recs and the transformer. I'd say this is what fried something internally in there.
Sorry I was afraid to mention this before but I realize that this is yet another learning curve for the rank beginner such as myself and I apologize for using some of your brainpower when you didn't have all the information.
I can only justify this behaviour in one way. That is after building this amazing thing and taking lots of very careful time about it I got to a ridiculous state of excitement and had to go at it like a bull at a gate that night. I already knew I should have just left it after the first attempt , asked lots of questions and I probably would have sorted it without causing all this damage. But I didn't so now I pay the price. At least I didn't get zapped by those caps going off.
So hopefully this is the last time I have to learn this lesson . Really apologize for not being totally up front with you guys. You are so helpful. Please forgive me.
Cheers.
Need help! I have read about 30 posts and other items and maybe just still dont get it. I have board sets that I purchased from BrianGT years back. I would like to build Dual Mono or Stereo setup of Aleph J or whatever is recommended? The boards are Aleph Mini x2 and the daughter boards x4. What are my options and are there any direct write ups?
Are those the black PCBs? (Can you post a pic?) If they are the ones I'm
thinking of then your obvious choices are mini aleph and aleph 30 and are
meant to be used with mosfet inputs.
Thanks Albert,G'day Wot,
I saw that your profile says you are in northern NSW. I am located between Brisbane and the Sunshine Coast, have a variac and some testgear. If you are in the area, bring your toroid and perhaps we can figure out what is going on
Cheers,
Albert
I'd like to take you up on that. Really appreciate this, PM sent, cheers, Dan
Last edited:
I agree with you. I am more interested in getting a variac though.
But I'm not sure what to aim for, do you have any recommendations?
I see some quite cheap ones on ebay but don't know what specs are going to be useful. For instance there are DC digital ones that only go to 30volts , these
are variable adjustable power supplies, or there are AC ones that will run 240 volts but they vary with KVa ratings. These are variable output transformers.
In a complete workshop no doubt one would need both types but can you say what most are referring to when they say variac here please?
A dim bulb tester is something you can easily assemble for very little cash and is great for limiting the current your circuit can draw. As current flows through the bulb it heats up and becomes more resistive. It also shows you when there is current flowing by lighting up. So simple yet so effective
At least 5-10 amp is what I would shoot for. The bulb tester has a slightly different role. The variac allows slow ramping up of voltage, which is helpful but components can still get fried. The dim bulb tester prevents damage at turn on. The bulb tester will protect your circuit . If it glows at first, then dies down, all is well. Remove it and use variac to slowly ramp up.if it glows and stays lite, there is a problem.
Assuming all went well, remove dim bulb and ramp up with variac.
Russellc
Assuming all went well, remove dim bulb and ramp up with variac.
Russellc
The variac in combination with a signal generator and AP System is very effective. Of course, not many DIY-ers can afford this gear; me neither - I am just recalling time I spent with electronics manufacturing company a few decades ago.... 
The bulb tester seems like a very sensible solution for DIY audio builds, especially if combined with a variac (and maybe a cheap-ish oscilloscope??)... but... the signal generator would be so handy as well... oh wait a minute, I am re-writing the first paragraph again.
The bulb tester seems like a very sensible solution for DIY audio builds, especially if combined with a variac (and maybe a cheap-ish oscilloscope??
)... but... the signal generator would be so handy as well... oh wait a minute, I am re-writing the first paragraph again.Variac and free signal generator on iPhone or android
I sent a link earlier for You Tube for Mr. Carlson’s lab about a bulb tester .
Here is a link how to use a variac and you might as well learn something about a isolation transformer while you’re at it .
Signal generators are available for your android or your iPhone for free . If you want to clean it up and boost to gain of the signal a little more you can run your cell phone through a DAC.
Tech Tips Tuesday, Isolation Transformer and Variac Safety - YouTube
I sent a link earlier for You Tube for Mr. Carlson’s lab about a bulb tester .
Here is a link how to use a variac and you might as well learn something about a isolation transformer while you’re at it .
Signal generators are available for your android or your iPhone for free . If you want to clean it up and boost to gain of the signal a little more you can run your cell phone through a DAC.
Tech Tips Tuesday, Isolation Transformer and Variac Safety - YouTube
Attachments
First power-up
It doesn't get mentioned very often and that is probably because most experienced builders do it automatically, but many first time builders do not. What I am referring to is powering up and testing in stages. That is, do not fully complete a project before powering it up for the first time. To maximize the chances of a successful build, build and test in stages. Build, test, if successful, then continue on to the next stage. That way you limit the amount of circuitry that needs trouble shooting. Most important, it can prevent an error in the power supply from blowing up the amplifier board.
In an amplifier, a logical first stage is the power supply. Test the power supply and make sure that it is supplying the correct voltages before continuing the build. The unloaded supply will output a voltage that is higher than the design operating voltage, maybe a few volts higher, depending on the transformer and value of the resistor in a CRC supply or dcr of the choke in a CLC supply. If the supply passes, then most people continue on. However, I usually test the supply another step by testing it under load. I determine the current demand of the amplifier and calculate the requirements of a dummy load resistor to be connected to the power supply for testing.
This is when knowledge of Ohm's Law is useful. Ohm's Law is the relationship between voltage, current, and resistance:
V=I*R, V=electromotive force in Volts, I=current in Amperes, R=resistance in Ohms
So if V=24V, I=1.7A,
V=I*R ---> R=V/I= 24V/1.7A=14.1 Ohms
For power rating, P=V*I= 24V*1.7A=40.8Watts
At this point I say, "Wow, that's a lot", so I would test it at say half the current (.85A) and the resistor power rating would be half at 20.4 Watts. For half the current, the resistance would double, in accordance with Ohm's Law so it would be 28.2 Ohms.
I have all sorts of 10Watt and 5Watt rectangular resistors that I've accumulated over the years so I would series and parallel some for approximately 28 Ohms and about 40 Watts. I usually provide a minimum of double the power rating to keep the resistors at a reasonable temperature.
Load testing of a unregulated power supply is probably not a critical requirement but if you are building a regulated power supply, then load testing is more important in order to make sure that the regulation circuit/circuits are functioning properly. Also a regulated supply circuit can be much more complicated than an unregulated supply circuit, and the circuit that it powers can also be complicated, so build and test in stages make trouble shooting easier, and greatly increase the probability of a successful build.
Bleed resistors were mentioned in previous posts, and Ohm's Law can be used to determine a value. Essentially a bleed resistor is a light load resistor (low current, say .01A) and the calculations would be as for the test load resistor above.
The LED resistor was also previously mentioned and Ohm's Law is also used to determine a value.
So Ohm's Law, a very simple equation, is very useful in diy electronics.
And build and test in stages. Do not power up your project for the first time when your project is 100% complete. And use a light bulb tester on first power-up.
It doesn't get mentioned very often and that is probably because most experienced builders do it automatically, but many first time builders do not. What I am referring to is powering up and testing in stages. That is, do not fully complete a project before powering it up for the first time. To maximize the chances of a successful build, build and test in stages. Build, test, if successful, then continue on to the next stage. That way you limit the amount of circuitry that needs trouble shooting. Most important, it can prevent an error in the power supply from blowing up the amplifier board.
In an amplifier, a logical first stage is the power supply. Test the power supply and make sure that it is supplying the correct voltages before continuing the build. The unloaded supply will output a voltage that is higher than the design operating voltage, maybe a few volts higher, depending on the transformer and value of the resistor in a CRC supply or dcr of the choke in a CLC supply. If the supply passes, then most people continue on. However, I usually test the supply another step by testing it under load. I determine the current demand of the amplifier and calculate the requirements of a dummy load resistor to be connected to the power supply for testing.
This is when knowledge of Ohm's Law is useful. Ohm's Law is the relationship between voltage, current, and resistance:
V=I*R, V=electromotive force in Volts, I=current in Amperes, R=resistance in Ohms
So if V=24V, I=1.7A,
V=I*R ---> R=V/I= 24V/1.7A=14.1 Ohms
For power rating, P=V*I= 24V*1.7A=40.8Watts
At this point I say, "Wow, that's a lot", so I would test it at say half the current (.85A) and the resistor power rating would be half at 20.4 Watts. For half the current, the resistance would double, in accordance with Ohm's Law so it would be 28.2 Ohms.
I have all sorts of 10Watt and 5Watt rectangular resistors that I've accumulated over the years so I would series and parallel some for approximately 28 Ohms and about 40 Watts. I usually provide a minimum of double the power rating to keep the resistors at a reasonable temperature.
Load testing of a unregulated power supply is probably not a critical requirement but if you are building a regulated power supply, then load testing is more important in order to make sure that the regulation circuit/circuits are functioning properly. Also a regulated supply circuit can be much more complicated than an unregulated supply circuit, and the circuit that it powers can also be complicated, so build and test in stages make trouble shooting easier, and greatly increase the probability of a successful build.
Bleed resistors were mentioned in previous posts, and Ohm's Law can be used to determine a value. Essentially a bleed resistor is a light load resistor (low current, say .01A) and the calculations would be as for the test load resistor above.
The LED resistor was also previously mentioned and Ohm's Law is also used to determine a value.
So Ohm's Law, a very simple equation, is very useful in diy electronics.
And build and test in stages. Do not power up your project for the first time when your project is 100% complete. And use a light bulb tester on first power-up.
First power-up
It doesn't get mentioned very often and that is probably because most experienced builders do it automatically, but many first time builders do not. What I am referring to powering up and testing in stages. That is, do not fully complete a project before powering it up for the first time. To maximize the chances of a successful build, build and test in stages. Build, test, if successful, then continue on to the next stage. That way you limit the amount of circuitry that needs trouble shooting. Most important, it can prevent an error in the power supply from blowing up the amplifier board.
In an amplifier, a logical first stage is the power supply. Test the power supply and make sure that it is supplying the correct voltages before continuing the build. The unloaded supply will output a voltage that is higher than the design operating voltage, maybe a few volts higher, depending on the transformer and value of the resistor in a CRC supply or dcr of the choke in a CLC supply. If the supply passes, then most people continue on. However, I usually test the supply another step by testing it under load. I determine the current demand of the amplifier and calculate the requirements of a dummy load resistor to be connected to the power supply for testing.
This is when knowledge of Ohm's Law is useful. Ohm's Law is the relationship between voltage, current, and resistance:
V=I*R, V=electromotive force in Volts, I=current in Amperes, R=resistance in Ohms
So if V=24V, I=1.7A,
V=I*R ---> R=V/I= 24V/1.7A=14.1 Ohms
For power rating, P=V*I= 24V*1.7A=40.8Watts
At this point I say, "Wow, that's a lot", so I would test it at say half the current (.85A) and the resistor power rating would be half at 20.4 Watts. For half the current, the resistance would double, in accordance with Ohm's Law so it would be 28.2 Ohms.
I have all sorts of 10Watt and 5Watt rectangular resistors that I've accumulated over the years so I would series and parallel some for approximately 28 Ohms and about 40 Watts. I usually provide a minimum of double the power rating to keep the resistors at a reasonable temperature.
Load testing of a unregulated power supply is probably not a critical requirement but if you are building a regulated power supply, then load testing is more important in order to make sure that the regulation circuit/circuits are functioning properly. Also a regulated supply circuit can be much more complicated than an unregulated supply circuit, and the circuit that it powers can also be complicated, so build and test in stages make trouble shooting easier, and greatly increase the probability of a successful build.
Bleed resistors were mentioned in previous posts, and Ohm's Law can be used to determine a value. Essentially a bleed resistor is a light load resistor (low current, say .01A) and the calculations would be as for the test load resistor above.
The LED resistor was also previously mentioned and Ohm's Law is also used to determine a value.
So Ohm's Law, a very simple equation, is very useful in diy electronics.
And build and test in stages. Do not power up your project for the first time when your project is 100% complete. And use a light bulb tester on first power-up.
It doesn't get mentioned very often and that is probably because most experienced builders do it automatically, but many first time builders do not. What I am referring to powering up and testing in stages. That is, do not fully complete a project before powering it up for the first time. To maximize the chances of a successful build, build and test in stages. Build, test, if successful, then continue on to the next stage. That way you limit the amount of circuitry that needs trouble shooting. Most important, it can prevent an error in the power supply from blowing up the amplifier board.
In an amplifier, a logical first stage is the power supply. Test the power supply and make sure that it is supplying the correct voltages before continuing the build. The unloaded supply will output a voltage that is higher than the design operating voltage, maybe a few volts higher, depending on the transformer and value of the resistor in a CRC supply or dcr of the choke in a CLC supply. If the supply passes, then most people continue on. However, I usually test the supply another step by testing it under load. I determine the current demand of the amplifier and calculate the requirements of a dummy load resistor to be connected to the power supply for testing.
This is when knowledge of Ohm's Law is useful. Ohm's Law is the relationship between voltage, current, and resistance:
V=I*R, V=electromotive force in Volts, I=current in Amperes, R=resistance in Ohms
So if V=24V, I=1.7A,
V=I*R ---> R=V/I= 24V/1.7A=14.1 Ohms
For power rating, P=V*I= 24V*1.7A=40.8Watts
At this point I say, "Wow, that's a lot", so I would test it at say half the current (.85A) and the resistor power rating would be half at 20.4 Watts. For half the current, the resistance would double, in accordance with Ohm's Law so it would be 28.2 Ohms.
I have all sorts of 10Watt and 5Watt rectangular resistors that I've accumulated over the years so I would series and parallel some for approximately 28 Ohms and about 40 Watts. I usually provide a minimum of double the power rating to keep the resistors at a reasonable temperature.
Load testing of a unregulated power supply is probably not a critical requirement but if you are building a regulated power supply, then load testing is more important in order to make sure that the regulation circuit/circuits are functioning properly. Also a regulated supply circuit can be much more complicated than an unregulated supply circuit, and the circuit that it powers can also be complicated, so build and test in stages make trouble shooting easier, and greatly increase the probability of a successful build.
Bleed resistors were mentioned in previous posts, and Ohm's Law can be used to determine a value. Essentially a bleed resistor is a light load resistor (low current, say .01A) and the calculations would be as for the test load resistor above.
The LED resistor was also previously mentioned and Ohm's Law is also used to determine a value.
So Ohm's Law, a very simple equation, is very useful in diy electronics.
And build and test in stages. Do not power up your project for the first time when your project is 100% complete. And use a light bulb tester on first power-up.
Pass DIY Addict
Joined 2000
Paid Member
All of the above information is great! I will add to it my own protocol for construction and first power up of an amplifier:
When populating the board:
Measure EVERY part before soldering into the board.
Install all resistors with value marking pointed up so they can be read if using Dale brown resistors.
Check all solder joints with a magnifying glass, making sure the solder has flowed smoothly across the solder pad.
Hold completed board up to a strong light, no light should be showing through any of the solder holes. If you see light, reflow the joint and add solder as needed.
Run a sharp-blade screwdriver between EVERY pairing of solder pads on the board. This removes any inadvertent solder bridges that might be hard to see.
For the power supply:
Always start with a fuse and a CL-60 in series with the primary of the transformer.
Verify the AC voltage of the secondary windings of the transformer.
Power down.
Connect the rectifier bridges to each secondary and add one set of caps along with a 2k2 3w bleeder resistor from +V to ground and from -V to ground. This prevents surprises. A ~20v power supply will take ~2-3 mins to power down with 2k2 resistors.
Power up and verify the +DC and -DC output of the PSU.
Once the PSU is working properly, power down. Wait for caps to drain.
Connect only a SINGLE amplifier channel to the PSU:
I use a dim-bulb tester AND my variac.
Start with variac at zero volts and ramp up (slowly) to 120v.
The bulb should come on (dimly) and you should be able to make some adjustments to bias and offset and see "some" difference in your measurements of bias (measured across source resistors for output mosfets) and speaker outputs.
At this point, the under-powered amp might be able to make some sort of music (though will likely be distorted or contain noise).
I tend to let things sit for a little while, spot check here and there for temperature on various resistors with a brief touch of the finger tip. None should be hot.
If it can make music, you're probably good to go with full voltage.
It may not yet make music, the PSU may not be high enough for the transistors to turn on.
Power down, remove the dim bulb tester, and fire up again, variac still in place.
Ramp the voltage up until your PSU measures about 10v, test again: does it produce music? Let it sit for a few minutes. All resistors still reasonable temperature?
Working in a quiet environment helps - you'll hear a resistor or transistor crackle if you cook it. Keep your nose close - you can sometimes smell a problem before you can see it.
If it makes some sort of music (always use a cheap speaker that you don't mind blowing), ramp up to 120v and do first rough set of bias and offset.
If anything goes wrong along the way, stop and double check everything on your board. Compare pinouts of transistors for proper orientation. Double check resistor markings and compare to schematic.
Somebody will probably add something that I overlooked here...
When populating the board:
Measure EVERY part before soldering into the board.
Install all resistors with value marking pointed up so they can be read if using Dale brown resistors.
Check all solder joints with a magnifying glass, making sure the solder has flowed smoothly across the solder pad.
Hold completed board up to a strong light, no light should be showing through any of the solder holes. If you see light, reflow the joint and add solder as needed.
Run a sharp-blade screwdriver between EVERY pairing of solder pads on the board. This removes any inadvertent solder bridges that might be hard to see.
For the power supply:
Always start with a fuse and a CL-60 in series with the primary of the transformer.
Verify the AC voltage of the secondary windings of the transformer.
Power down.
Connect the rectifier bridges to each secondary and add one set of caps along with a 2k2 3w bleeder resistor from +V to ground and from -V to ground. This prevents surprises. A ~20v power supply will take ~2-3 mins to power down with 2k2 resistors.
Power up and verify the +DC and -DC output of the PSU.
Once the PSU is working properly, power down. Wait for caps to drain.
Connect only a SINGLE amplifier channel to the PSU:
I use a dim-bulb tester AND my variac.
Start with variac at zero volts and ramp up (slowly) to 120v.
The bulb should come on (dimly) and you should be able to make some adjustments to bias and offset and see "some" difference in your measurements of bias (measured across source resistors for output mosfets) and speaker outputs.
At this point, the under-powered amp might be able to make some sort of music (though will likely be distorted or contain noise).
I tend to let things sit for a little while, spot check here and there for temperature on various resistors with a brief touch of the finger tip. None should be hot.
If it can make music, you're probably good to go with full voltage.
It may not yet make music, the PSU may not be high enough for the transistors to turn on.
Power down, remove the dim bulb tester, and fire up again, variac still in place.
Ramp the voltage up until your PSU measures about 10v, test again: does it produce music? Let it sit for a few minutes. All resistors still reasonable temperature?
Working in a quiet environment helps - you'll hear a resistor or transistor crackle if you cook it. Keep your nose close - you can sometimes smell a problem before you can see it.
If it makes some sort of music (always use a cheap speaker that you don't mind blowing), ramp up to 120v and do first rough set of bias and offset.
If anything goes wrong along the way, stop and double check everything on your board. Compare pinouts of transistors for proper orientation. Double check resistor markings and compare to schematic.
Somebody will probably add something that I overlooked here...