I wanted to measure some voltage values over resistors. To see if the soldering was good, of if the PCB was correct.
So I did apply a rails to the PCB, but without the mosfets. Because my heatsink are not there yet. I did measure some values, but the Diff pair transistors Q1 and Q2 were different in Temperature. Q1 got hot, and Q2 did not have increase in temp.
It was te same for the left and Right channel. Is this due to te fact that de power transistors were not installed? Or could there anything else be the problem. I don't think it's one of the IRFP9610 fets, beacause it's in both channels.
Please some comments, Tips, and suggestions.
Thanks,
Nils
So I did apply a rails to the PCB, but without the mosfets. Because my heatsink are not there yet. I did measure some values, but the Diff pair transistors Q1 and Q2 were different in Temperature. Q1 got hot, and Q2 did not have increase in temp.
It was te same for the left and Right channel. Is this due to te fact that de power transistors were not installed? Or could there anything else be the problem. I don't think it's one of the IRFP9610 fets, beacause it's in both channels.
Please some comments, Tips, and suggestions.
Thanks,
Nils
Differential pair inputs try to equalize to each other, so if one of your inputs is at 'some potential' then the other input will try to follow. Without the feedback from the output I suspect that the one input is trying to compensate for the high voltage on the other input and all the differential tail current is going through one of the differential transistors causing it to dissipate more heat.
I dont have the Aleph 30 print in front of me, but if you could provide a zero potential at the input to Q2 then the differential pair should operate with more equal currents. On the Aleph 3 you can short across C101, 220uF. This is of course if the output devices are still not in the circuit. I did something similar when I constructed my Aleph. I like to test as many parts as I can before bringing the whole thing up at full voltage.
BDP
I dont have the Aleph 30 print in front of me, but if you could provide a zero potential at the input to Q2 then the differential pair should operate with more equal currents. On the Aleph 3 you can short across C101, 220uF. This is of course if the output devices are still not in the circuit. I did something similar when I constructed my Aleph. I like to test as many parts as I can before bringing the whole thing up at full voltage.
BDP
Do I really need an input? because I only want to test the circuit on de value's over some components. To see if they are the same as other people had.
So shorting the cap C101 from the Aleph 3 amp would be same bypasing the two diodes? (aleph 30)
Nils
So shorting the cap C101 from the Aleph 3 amp would be same bypasing the two diodes? (aleph 30)
Nils
This weekend it's going to happen!
Testing the amp!
Does anyone have some values which I can check!
The rails is about 25 V according to Duncans program. The schematic is the Aleph 30 and I will ise the IRFP140 Mosfets.
What is the best way to Test the circuit? Just 1 channel at the time? Do I need to have an input, like an sinus or just any input?
Please give some hints.
Thanks
Nils
Testing the amp!
Does anyone have some values which I can check!
The rails is about 25 V according to Duncans program. The schematic is the Aleph 30 and I will ise the IRFP140 Mosfets.
What is the best way to Test the circuit? Just 1 channel at the time? Do I need to have an input, like an sinus or just any input?
Please give some hints.
Thanks
Nils
burned Source resistors
Hello,
Just applied 20V rails and burned two Source resistors.
The two resistors are conected at the negative rails, and burned within 10 sec.
Voltage is +- 21.4 V
There was no input conected
There was a 30 W 8 ohm resistor at the output.
Please help what could be wrong???????
Nils
Hello,
Just applied 20V rails and burned two Source resistors.
The two resistors are conected at the negative rails, and burned within 10 sec.
Voltage is +- 21.4 V
There was no input conected
There was a 30 W 8 ohm resistor at the output.
Please help what could be wrong???????
Nils
Nils,
Were you able to test the front end as per previous posts? What's the wattage on the source resistors? Sorry, have to ask. Obviously, if the resistors are of enough wattage, you are drawing too much current. Were you monitoring the voltage across the source resistors before they gave it up? This could be from to much voltage across 390 ohm differential drain resistor. What other measurements were you taking?
BDP
Were you able to test the front end as per previous posts? What's the wattage on the source resistors? Sorry, have to ask. Obviously, if the resistors are of enough wattage, you are drawing too much current. Were you monitoring the voltage across the source resistors before they gave it up? This could be from to much voltage across 390 ohm differential drain resistor. What other measurements were you taking?
BDP
Up and running
Finally My first DIY (Aleph 30) project is up and running!
Post Pictures soon.
Rails both channels +- 24.4 V (right) 24.3 V (left)
6 x IRFP140 / Channel
DC at the output 50 mV Left, 80 mV Right
heatsinks get hot ( I think 55 ° C) Still have to measure.
The sound is Very nice, clear, and the staging is much greater than the NAD 317. There is much air in the sound, don't know how to explain this.
The only thing is that there is a plop when turnig the amp on en an even harder plop when I turn off the Amplifier. I Didn't install the Thermistors jet because they were not available at the time. Do those Thermistors (cl-60) prevent the output to plop? Or is there another way to avoid this plopping sound. I think it's not healthy for the speakers.
And there is a slight hum in the amp. audible just at the speakers. There is no resistor or choke used in the powersupply. I think the sound comes from a vibrating transformer which I can hear also, even if speakers are not conected.
Nils
Finally My first DIY (Aleph 30) project is up and running!
Post Pictures soon.
Rails both channels +- 24.4 V (right) 24.3 V (left)
6 x IRFP140 / Channel
DC at the output 50 mV Left, 80 mV Right
heatsinks get hot ( I think 55 ° C) Still have to measure.
The sound is Very nice, clear, and the staging is much greater than the NAD 317. There is much air in the sound, don't know how to explain this.
The only thing is that there is a plop when turnig the amp on en an even harder plop when I turn off the Amplifier. I Didn't install the Thermistors jet because they were not available at the time. Do those Thermistors (cl-60) prevent the output to plop? Or is there another way to avoid this plopping sound. I think it's not healthy for the speakers.
And there is a slight hum in the amp. audible just at the speakers. There is no resistor or choke used in the powersupply. I think the sound comes from a vibrating transformer which I can hear also, even if speakers are not conected.
Nils
Hello Nils,
first of all compliments for building this nice amp!
The vibration of the transformer can be caused by the saturation of the core for a fraction of the 50Hz cycle.
This saturation can be caused by a slight imbalance of the secondaries, when they are used with a single rectifier bridge.
Using two bridges (one per rail) helped me solving this problem.
A thermistor in series with the primary winding also helps, my amp has a "plop" too but is not that hard.
Cheers
Andrea
first of all compliments for building this nice amp!
The vibration of the transformer can be caused by the saturation of the core for a fraction of the 50Hz cycle.
This saturation can be caused by a slight imbalance of the secondaries, when they are used with a single rectifier bridge.
Using two bridges (one per rail) helped me solving this problem.
A thermistor in series with the primary winding also helps, my amp has a "plop" too but is not that hard.
Cheers
Andrea
wijgers said:
That "plop" is not good for your woofers. I used a switch on the output to solve this. It is a dual on-on switch. One position goes to the speakers, the other to a power resistor.
This way a 25 watt 10 ohm resistor gets the power up and down transients. If you solve this issue, the resistor can be left on the on position.
The dual switch is used to place the output on two sets of contacts. Less likely to open.
There are much more elegant ways to do this. But it works for me.
George
rectifier bridge ripple!
I'm using one rectifier bridge per transformer, and made of 4 MBR1090 Diodes. Rated at diodes 90 V and 10 A. Are those diodes not fast enough or are other characteristics not good for my amp?
There still is a little hum and when I connect - input at gnd it gives a louder hum (50 Hz). this Hum I can hear at 2 meters.
The rectifer bridge is not cooled yet, but will be soon. For the rest I don't see any troubles where the hum can be produced from.
What can I do to reduce the hum.
RCA connected or disconnected gives no difference.
Nils
I'm using one rectifier bridge per transformer, and made of 4 MBR1090 Diodes. Rated at diodes 90 V and 10 A. Are those diodes not fast enough or are other characteristics not good for my amp?
There still is a little hum and when I connect - input at gnd it gives a louder hum (50 Hz). this Hum I can hear at 2 meters.
The rectifer bridge is not cooled yet, but will be soon. For the rest I don't see any troubles where the hum can be produced from.
What can I do to reduce the hum.
RCA connected or disconnected gives no difference.
Nils
bridges
Andrea,
You sugest to use 2 bridges per transformer, so I need 4 rectifier bridges in this amp.
Didn't change anything yet due some lack of time. Probably this weekend I will try to add the themistors an change the gnd schematics. like I saw at the aleph 5 gnd problem thread. Maybe there is a pickup from the vibrating transformer. When everything wasn't not in a box I did still hear some hum.
nils
Andrea,
You sugest to use 2 bridges per transformer, so I need 4 rectifier bridges in this amp.
Didn't change anything yet due some lack of time. Probably this weekend I will try to add the themistors an change the gnd schematics. like I saw at the aleph 5 gnd problem thread. Maybe there is a pickup from the vibrating transformer. When everything wasn't not in a box I did still hear some hum.
nils
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