Hello all and thanks for this great forum;
I'm a long time reader but first time poster
Here you can see some pics of my aleph 2. The amp is finished but when I turn it on, the woofer of the speaker "pops out" .Without any imput signal you can see the speaker at its maximum excursion permanently, it's not centered. If you conect the preamp to the amp, you can hear music, but it distorts because the woofer it's allready at its maximum excursion.
I have replaced all the irf9610 and bc55. I have replaced everything except the irfp240.
Even i have replaced the pcb's.
Can that be caused by a faulty irfp240?
Te irf9610 measure like this:
Q2:
GS= 4,1
GD=56,8
DS=60
Q1:
GS= 4,1
GD=55,8
DS=55,6
Q3:
GS= 4,1
GD=45,7
DS=45,2
Please i need help, i spend tons and tons of hours on this great amp
Also here you have more measurements and pics:
I'm a long time reader but first time poster
Here you can see some pics of my aleph 2. The amp is finished but when I turn it on, the woofer of the speaker "pops out" .Without any imput signal you can see the speaker at its maximum excursion permanently, it's not centered. If you conect the preamp to the amp, you can hear music, but it distorts because the woofer it's allready at its maximum excursion.
I have replaced all the irf9610 and bc55. I have replaced everything except the irfp240.
Even i have replaced the pcb's.
Can that be caused by a faulty irfp240?
Te irf9610 measure like this:
Q2:
GS= 4,1
GD=56,8
DS=60
Q1:
GS= 4,1
GD=55,8
DS=55,6
Q3:
GS= 4,1
GD=45,7
DS=45,2
Please i need help, i spend tons and tons of hours on this great amp
Also here you have more measurements and pics:
Attachments
You can test the IRFPs by measuring the volt drop across each source resistor.
Don't use your speakers until you have sorted out the DC offset.
Don't use your speakers until you have sorted out the DC offset.
my guess is that you have a big DC offsett.
and you may also have a cooling problem. those sinks looks way to smal.
and you may also have a cooling problem. those sinks looks way to smal.
What are the voltages across R11 and R14 ?
The heatsink issue will rear its ugly head as we get the thing working.
As long as its not blowing fuses and roasting components it should be OK for the short tests that we are going to perform.
The heatsink issue will rear its ugly head as we get the thing working.
As long as its not blowing fuses and roasting components it should be OK for the short tests that we are going to perform.
hello and thanks for your help!
R11 is 6,8v
R14 is 5v
Some more measurements are shown in the attached scheme
The 1 ohm resistors are between 0,45 an 0,43v
The four lateral heatsinks are rated Cº/W 0,11 each. Maybe I could help them with fans ;P
You are right Jacco, as soon as I can I'll measure again the 9610's
Ah! the loudspeaker I'm using its just for testing purpouses
Pd: sorry for my bad english
R11 is 6,8v
R14 is 5v
Some more measurements are shown in the attached scheme
The 1 ohm resistors are between 0,45 an 0,43v
The four lateral heatsinks are rated Cº/W 0,11 each. Maybe I could help them with fans ;P
You are right Jacco, as soon as I can I'll measure again the 9610's
Ah! the loudspeaker I'm using its just for testing purpouses
Pd: sorry for my bad english
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it looks like a modushop 5U 500mm chassis. and they are rated 0.11C/W pr SIDE
and thats at 80C above ambient.
more realistic its about 0.15-0.16C/W pr side.
and thats at 80C above ambient.
more realistic its about 0.15-0.16C/W pr side.
measures source resistor:
Bias Board:
r-40= 0,534
r-41= 0,533
r-42= 0.421
r-43= 0,584
r-44= 0,499
r-45= 0,438
Output board
r-46= 0,497
r-47= 0,467
r-48= 0,526
r-49= 0,410
r-50= 0,558
r-51= 0,715
Thanks for your interest I'm desperate.
Bias Board:
r-40= 0,534
r-41= 0,533
r-42= 0.421
r-43= 0,584
r-44= 0,499
r-45= 0,438
Output board
r-46= 0,497
r-47= 0,467
r-48= 0,526
r-49= 0,410
r-50= 0,558
r-51= 0,715
Thanks for your interest I'm desperate.
Did you match the output devices or just throw them in ?
The 715mV is way off, but the others show +35% spread.
Iznogood
The 715mV is way off, but the others show +35% spread.
Iznogood
Hello again, and thanks again 8)
Yep, bingo! the chassis is a modushop 5U 500mm. So definetively i should go with fans ouch! At least its pretty!
Jacco, the output mossfet aren't matched, I just throw them in...Do you think that this can be the problem? maybe I'm out of luck and that mossfet is out of specs.
As soon as I can I'll change the mossfet connected to r-51and see what happens.
I've measured again the irf9610:
Q2:
GD=56,4
GS=4,23
DS=60,8
Q1:
GD=50,9
GS=4,20
DS=56,2
Q3:
GD=42
GS=4,20
DS=46,1
Yep, bingo! the chassis is a modushop 5U 500mm. So definetively i should go with fans ouch! At least its pretty!
Jacco, the output mossfet aren't matched, I just throw them in...Do you think that this can be the problem? maybe I'm out of luck and that mossfet is out of specs.
As soon as I can I'll change the mossfet connected to r-51and see what happens.
I've measured again the irf9610:
Q2:
GD=56,4
GS=4,23
DS=60,8
Q1:
GD=50,9
GS=4,20
DS=56,2
Q3:
GD=42
GS=4,20
DS=46,1
Which brings up a question, on the Aleph 2, (Which I am collecting parts for slowly) How are these output devices matched? I dont mean matching procedure, but what is matched with what? I began to get confused reading the service manual, where it stated, "matched in pairs" could someone tell me what I need in terms of output device matching for an Aleph 2?
Thanks for any help,
Russellc
Hi,
At the beginning of your thread you said that the speaker goes to "speaker at its maximum excursion permanently". The output reading is " +0,02v and +0,016 " then what king of speaker you have that the cone goes all the way out permanently with a 200mv. So you have 200 mv and the speaker goes all the way out. I think 200 mv will not move the cone in the way you described it. It is possible that you can heard small hum sound. Something it is not right or I am misunderstanding what you mean by all the way out. It this happened only when you power the amplifier on?
At the beginning of your thread you said that the speaker goes to "speaker at its maximum excursion permanently". The output reading is " +0,02v and +0,016 " then what king of speaker you have that the cone goes all the way out permanently with a 200mv. So you have 200 mv and the speaker goes all the way out. I think 200 mv will not move the cone in the way you described it. It is possible that you can heard small hum sound. Something it is not right or I am misunderstanding what you mean by all the way out. It this happened only when you power the amplifier on?
Hi,
OOOpss! Zen Mod your are right. It is 20mv and 16mv not 200mv. If this is the output reading I think the amplifier does not have any problem. The 16mv to 20mv it is normal for a amplifier output. It could better but it sound not moved the speaker cone all the way out and stay out.
OOOpss! Zen Mod your are right. It is 20mv and 16mv not 200mv. If this is the output reading I think the amplifier does not have any problem. The 16mv to 20mv it is normal for a amplifier output. It could better but it sound not moved the speaker cone all the way out and stay out.
hello again!
Tauro0221 you did not missunderstand 8) . The speaker I'm using is a polypropilene 5" midwoofer from a tannoy conected directly to the amp, I think it's 89db.
When I turn on the amp, the speaker slowly moves forward aproximately 4 milimeters (it takes obout a couple of seconds). So the midwoofer's voice coil is not centered.
If I put audio signal, the midwoofer's voice coil already has an offset of 4mm quickly reach it's Xmax, so it quickly distorts.
.
The voltimeter was set on DC when I measured between output and ground... It's that ok or i should set the voltimeter on AC?
Thanks for your patience
PD: somethin really strange is happening lol. I won't be able to do any measurement in the next 48 hrs.
Tauro0221 you did not missunderstand 8) . The speaker I'm using is a polypropilene 5" midwoofer from a tannoy conected directly to the amp, I think it's 89db.
When I turn on the amp, the speaker slowly moves forward aproximately 4 milimeters (it takes obout a couple of seconds). So the midwoofer's voice coil is not centered.
If I put audio signal, the midwoofer's voice coil already has an offset of 4mm quickly reach it's Xmax, so it quickly distorts.
.
The voltimeter was set on DC when I measured between output and ground... It's that ok or i should set the voltimeter on AC?
Thanks for your patience
PD: somethin really strange is happening lol. I won't be able to do any measurement in the next 48 hrs.
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DC is what you need to measure , but 20 and 16mV aren't enough for 4mm of cone push
measure again
measure again
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