Aleph 5 won´t play

[Franz]

Hello Aleph builder club!

I have trouble bringing my just finished aleph 5 to live.
When connected to power I can meassure almost no bias current. Additionally I have full positive rail voltage at the output!
Thank god I didn´t connect a speaker.
Something must have gone completely wrong here!

Could zeners with too lower power rating be the reason? I used the smallest types (500 mW I guess) and empoly KRISTIJAN´s A5 boards. All Fets were tested before soldering.

Any help /opinion is greatly appreciated. Thanks in advance!


Franz

[SkinnyBoy]

umm... did you wire the transformer properly?

[Franz]

Hi Skynnyboy,

yes, PS should be wired correctly.
I have about +- 36 V rail voltage.

Franz

[SkinnyBoy]

And you get +36volts on the output? lol... hmmm..

[Netlist]

Hi Franz

I would start measuring the voltages as listed in the original schematic: 4-5V across R11, 9V across the Z5, 4-5V across Q5.

Maybe you can give us some more details.

/Hugo - Knows how it feels when things don't work

[Jay]

My first post.

My experience told me that if I encountered problems such as yours, what I need was just a refreshing moment. I would get out or continue on the next day, and would find out that it was just a simple silly mistake.

Based on the experience, I expected you to have answered your own question. But may be the situation is diferent! Then you may need to give exact data for others to assist you solve the problem. You said you measured + rail on the output? Did you mean a "shortage" between Drain and Source of the signal MOSFET? Or else?

[Wes Marquenie]

Check the pair of irf9610's...

[kirc]

Sit back and relax, then go to work

First of all check the orientations of Q1 to Q5. Take a look on PSU to A5 PCB wire connection, then check the voltage ratings on all transistors.
Aleph 5 works fine - there must be your error why doesn't work

After this test send us more information.

best regards,
LEON

[kristijan-k]

Hello Mr.Stolz,

The power rating of the zener diode could be even 500 mW, and this is
not the reason that your amplifier did not worked from the beginning.
It is 99 % probably an human error during construction,
and not part defect.

Also, there can be a numerous reasons why it comes to the point that
amplifier refuses to work.
When soldering any mosfet tranzistor, you should do that with the soldering iron
grounded, just in any case to avoid static electricity that can damage the
mosfets.

Also, do not heat the transistors and diodes more than required.

You should check for the correct diode orientation, and check the all
resistors and diodes with the Multimeter.
In some cases some colors can look like very similar and it is very
difficult to tell which one it is, especially on the metal-film types.

Check that the all transistors are electricaly isolated from their
heatsinks.

Also, if you have any higher voltage at the output (like very high offset),
you should desolder all the transistors and then check each one separately
for their proper operation.

Before another power up, check the power supply for the right voltages.

Before any first power up try to check everything several times,
no matter how long it would take and how that is boring, at the end it can
save you a lot's of your time and nervs.


Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip

[uli]

Originally posted by Franz
Hello Aleph builder club!

I have trouble bringing my just finished aleph 5 to live.
When connected to power I can meassure almost no bias current. Additionally I have full positive rail voltage at the output!

I had once the same thing
Reason: reverse positioned zenerdiode in the diff. current source.
Leads to no current in diff pair -> no current in output devices
-> maximum positive voltage on output!
Turn this zener!

Uli