Hello Pass fans,
I somehow burned my Aleph 3 clone few days ago.
Now the right channel outputs +24VDC.
I changed the 3 IRF9610 and 2 MPSA18.
I checked the IRFP244s. Seems to be good.
But still no help.
The voltage across R106 and R108 is now only 1V.
The voltage at the D-leg of Q103 is 3V.
The voltage at the G-leg of Q102 is 9V.
The voltage across Q105 is 3.5V
The voltage across Z103 is 4V
Could anyone help please?
Thanks!
Jesse
I somehow burned my Aleph 3 clone few days ago.
Now the right channel outputs +24VDC.
I changed the 3 IRF9610 and 2 MPSA18.
I checked the IRFP244s. Seems to be good.
But still no help.
The voltage across R106 and R108 is now only 1V.
The voltage at the D-leg of Q103 is 3V.
The voltage at the G-leg of Q102 is 9V.
The voltage across Q105 is 3.5V
The voltage across Z103 is 4V
Could anyone help please?
Thanks!
Jesse
What happened that caused the amp to misbehave?
Assuming you have + and - 25V supply,
I still guess your problem is in the front-end.
There is not a lot that can break in the input.
Make sure you connected everything correctly. (Bad solderings, earth)
What's the voltage across the feedback resistor?
/Hugo
Assuming you have + and - 25V supply,
I still guess your problem is in the front-end.
There is not a lot that can break in the input.
Make sure you connected everything correctly. (Bad solderings, earth)
What's the voltage across the feedback resistor?
/Hugo
I had a similar problem when I built my power amps, all the components we fine but the thing didnt work. The problem was in the PCB there was a tiny tiny break in one of the tracks (you couldnt see it but measure it you could), this sorted out the thing sang like all the other 4 channels did. Anyway could it be possible that you have got all the components working but in the listening process you managed to burn out a track that wasnt etched verywell. My boards were my 1st so they had some discontinueties your mite be fine. Anyway just my $0.02.
Yes, the zeners are there to protect the diff-pair from overvoltage and spikes, but they also can break.
You'll have to check your connections IMO.
Be careful with mosfets and ESD. Discharge the PSU-caps before
soldering something in and out. There's a good chance that 5 to 10 V remains at them after you power off. Get rid of that voltage
or you might damage your new fets when soldering them in.
You could try to disconnect your output mosfets and only power up your front-end.
Work carefully, try to power up with a variac and yes, check the pcb for bad traces. (Can be very difficult)
Any pictures perhaps?
/Hugo
You'll have to check your connections IMO.
Be careful with mosfets and ESD. Discharge the PSU-caps before
soldering something in and out. There's a good chance that 5 to 10 V remains at them after you power off. Get rid of that voltage
or you might damage your new fets when soldering them in.
You could try to disconnect your output mosfets and only power up your front-end.
Work carefully, try to power up with a variac and yes, check the pcb for bad traces. (Can be very difficult)
Any pictures perhaps?
/Hugo
Back again with some voltage measurements (with respect to the ground):
G/D/S
Q101 0/-24/-15 Q102 -15/-24/-15 Q103 +24/-15/+24
C/B/E
Q104 -24/-24/-24 Q105 -18/-24/-24
G/D/S
Q106 +22/-24/+20 Q107 -23/+24/-19
Q108 -24/-24/-24 Q109 -24/-24/-24
Hugo:
Thanks, I will do the MOSFETs check again with longer waiting time.
5th Element:
Thanks for your input. I will check again the PCB.
G/D/S
Q101 0/-24/-15 Q102 -15/-24/-15 Q103 +24/-15/+24
C/B/E
Q104 -24/-24/-24 Q105 -18/-24/-24
G/D/S
Q106 +22/-24/+20 Q107 -23/+24/-19
Q108 -24/-24/-24 Q109 -24/-24/-24
Hugo:
Thanks, I will do the MOSFETs check again with longer waiting time.
5th Element:
Thanks for your input. I will check again the PCB.
Doesn't sound as though the front end current source is working. Without it driving the differential, you're guaranteed that nothing else will work, as there'll be too little voltage drop across R108 and the outputs won't bias, and if they're not working, then...
Assuming that the rails are at full voltage, then Q103's Gate should show the nominal voltage (9V below the positive rail, or about +16V measured from ground assuming that the rail is 25V). Z103 and R105 are a tidy little subunit, and should work regardless of what else is going on. If they aren't then you have a problem in that area.
Possibilities:
--R105 is toast
--Z103 is toast
--Bad solder joints or traces (Just for the heck of it, I vote for a cold solder joint. Use a solder sucker or solder wick and clean the joints, then reflow with fresh solder.)
--Q103 is toast (if it somehow managed to short G/S, then it could be bogging down the Zener voltage)
--R107 might be bad, but somehow that doesn't seem likely
What to do? You might try removing R107 and tie Q103's Gate to the +rail, just to keep it from wandering off and getting lost. See if the R105/Z103 pair pops up to the right voltage. It doesn't sound as though the rest of the amp is coming up anyway, so it's not likely to do any harm to the rest of the circuit. If the reference doesn't work, start prodding around those two parts. If it does work, then test Q103 out of circuit and make sure it works. Until the Gate on Q103 swings down from the rail, you know the current source isn't going to work, and until it turns on the rest of the amp won't go anywhere.
Grey
Assuming that the rails are at full voltage, then Q103's Gate should show the nominal voltage (9V below the positive rail, or about +16V measured from ground assuming that the rail is 25V). Z103 and R105 are a tidy little subunit, and should work regardless of what else is going on. If they aren't then you have a problem in that area.
Possibilities:
--R105 is toast
--Z103 is toast
--Bad solder joints or traces (Just for the heck of it, I vote for a cold solder joint. Use a solder sucker or solder wick and clean the joints, then reflow with fresh solder.)
--Q103 is toast (if it somehow managed to short G/S, then it could be bogging down the Zener voltage)
--R107 might be bad, but somehow that doesn't seem likely
What to do? You might try removing R107 and tie Q103's Gate to the +rail, just to keep it from wandering off and getting lost. See if the R105/Z103 pair pops up to the right voltage. It doesn't sound as though the rest of the amp is coming up anyway, so it's not likely to do any harm to the rest of the circuit. If the reference doesn't work, start prodding around those two parts. If it does work, then test Q103 out of circuit and make sure it works. Until the Gate on Q103 swings down from the rail, you know the current source isn't going to work, and until it turns on the rest of the amp won't go anywhere.
Grey
Thanks guys!
Hugo,
actually the voltages from the middle line (output) down are all nearly -24V...
Nelson,
this amp has serviced me for 10 months with lots of pleasure. The other channel is working peoperly. Actually it's a dual-mono version. So everything is independant from each channel.
Grey,
I will follow your instructions to check the parts tonight.
Results will be reported as soon as it's available.
I am glad I'm in the Pass DIY family. This guarrantees I'll never be alone.
Hugo,
actually the voltages from the middle line (output) down are all nearly -24V...
Nelson,
this amp has serviced me for 10 months with lots of pleasure. The other channel is working peoperly. Actually it's a dual-mono version. So everything is independant from each channel.
Grey,
I will follow your instructions to check the parts tonight.
Results will be reported as soon as it's available.
I am glad I'm in the Pass DIY family. This guarrantees I'll never be alone.
My Aleph 3 is back to service!!
Just look at my face, you should know the results...
Grey,
I followed your instruction and checked the Z103, which I changed a couple days ago. Without the connection to R107, Z103 fails to provide 9V, but 4V instead.After I changed to a new Zener, the voltage comes back to 9V. Then I knew that I have to forget all those parts I have changed, and start from beginning.
I connected the R107 back, then the voltage dropped to 4V. So I took off the Q103. Mesurements shows the G/S is short. Then I changed to a new IRF9610. So far, it happened exactly as Grey's post. Although I still get -24V output, but I knew I'm on the right track.
Then Q102 & Q109 were both found toast.
After changed Q102 & Q109, I powered on the Aleph and measured the output.....Wohoho...No +24V no -24V... I knew this little beast has come back..
Hugo, I think you are right. Those new MOSFETs might be damaged by the remaining voltage in the PSU. So this time I discharged those big caps to under 0,1V before I change anything.
I don't know how to post the pics. But if you are interested, here is the link: http://www.passdiy.com/gallery/aleph3-p4.htm
Thanks guys! I must leave now because the music is playing...
Jesse
Just look at my face, you should know the results...
Grey,
I followed your instruction and checked the Z103, which I changed a couple days ago. Without the connection to R107, Z103 fails to provide 9V, but 4V instead.After I changed to a new Zener, the voltage comes back to 9V. Then I knew that I have to forget all those parts I have changed, and start from beginning.
I connected the R107 back, then the voltage dropped to 4V. So I took off the Q103. Mesurements shows the G/S is short. Then I changed to a new IRF9610. So far, it happened exactly as Grey's post. Although I still get -24V output, but I knew I'm on the right track.
Then Q102 & Q109 were both found toast.
After changed Q102 & Q109, I powered on the Aleph and measured the output.....Wohoho...No +24V no -24V... I knew this little beast has come back..
Hugo, I think you are right. Those new MOSFETs might be damaged by the remaining voltage in the PSU. So this time I discharged those big caps to under 0,1V before I change anything.
I don't know how to post the pics. But if you are interested, here is the link: http://www.passdiy.com/gallery/aleph3-p4.htm
Thanks guys! I must leave now because the music is playing...
Jesse
Music here.
Well Hugo,
There are big variety of music here in Taiwan. Classical, Jazz, Country, Ragae, Rock, ... whatever you name out...
As I travel in Europe quite often, I learned that the music type in Europe is in some ways a little different than here. I would say Taiwanese people get more influence from States.
Local singers are also good, but mainly in Chinese though (definitely not for western people). They have been quite successful in the Chinese comunity, i.e. Taiwan, Hongkong, Singpore, China, ...
By the way, the CD price here is lower than the price in Europe. (Of course the CD price in China is even lower, but that's another story), However, the LP price here is higher than the price in Europe. So now my German friends buy CDs here and I buy LPs there....
Jesse
Well Hugo,
There are big variety of music here in Taiwan. Classical, Jazz, Country, Ragae, Rock, ... whatever you name out...
As I travel in Europe quite often, I learned that the music type in Europe is in some ways a little different than here. I would say Taiwanese people get more influence from States.
Local singers are also good, but mainly in Chinese though (definitely not for western people). They have been quite successful in the Chinese comunity, i.e. Taiwan, Hongkong, Singpore, China, ...
By the way, the CD price here is lower than the price in Europe. (Of course the CD price in China is even lower, but that's another story), However, the LP price here is higher than the price in Europe. So now my German friends buy CDs here and I buy LPs there....
Jesse
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