Aleph J illustrated build guide

[bbm3]

It seems to me that maybe there is a grounding anomaly that these two devices together aren't happy with.

Could you try modding an RCA cable so the grounds don't connect and only the center conductors do?
For testing purposes only of course.....

I can do that.

R6 and R30 - I'd suggest 0 ohms for the time being because this is likely a ground issue, because the amplifier works properly with other preamps...


How is audio ground connected to chassis in AJ?

Are all the devices plugged into the same power strip?

Audio IN ground is connected to the pad IN-


I'll post a picture later today. Thanks everyone for the help!

 

[bbm3]

R6 and R30 - I'd suggest 0 ohms for the time being because this is likely a ground issue, because the amplifier works properly with other preamps...


How is audio ground connected to chassis in AJ?

Are all the devices plugged into the same power strip?

Sorry I missed the last question. I am not sure if they were connected to the same wall outlet. Same house circuit but could have been a different outlet.

Additionally the boards are currently out of the chassis and the F6's are in place so I will need some time to swap boards for further troubleshooting.

Thanks again for the help Ill post back when I have the AJ running.

 

[chede]

Audio IN ground is connected to the pad IN-

In case you maybe haven't done so already, IN- should also be connected to GND directly on the PCB.


Regards,
Claas

 

[Morenmgu]

Strong Noise

Hello all !!

I need your experice for try to solve a problem. As you know, I build an Alepj J some months ago, and I'm very very happy with it, but yestarday, like other day, I use the power amp for about 3-4 hours without any problem.

Today when I turn on, on left chanel, sound a strong noise, not much high, not much low, where do you recommend start to revise each per each component ?? Any similiar problem.

Thanks for your help.

 

[Zen Mod]

first try to look for any suspicious connection - wires etc.

after that , any suspicious solder point

after that, some measurements, but only after you post some pics, so we can see how you arranged several positions with optional parts placement

 

[Dennis Hui]

Check for wiring/soldering issues to start as ZM suggested. I had a loud buzzing channel in an F6 build
after a few months use and it was a cold solder joint at the binding post.

 

[Morenmgu]

I check all conections, all wires, change wires, rca wire, chan gin wire chanel, change preamp.... I can't see any visual problem, maybe one capacitor.... but it's rare, yesterday was working well the only change was for test 4ohm monitors....

 

[Zen Mod]

mica insulators?

can't see that you have thermal goo on both sides of mica

 

[Morenmgu]

Yes, 4 mica insulators and thermal paste...

 

[Dennis Hui]

I can't tell if you're using any standoffs. Is the clearance between heatsink and pcb and all wiring and parts ok?

 

[Zen Mod]

I can't see any goo between mosfet and mica, but if you say it's there, then OK

with inputs shorted- can you measure output DC offset , and voltage across all 4 mosfet source resistors?

 

[Morenmgu]

I think yes, all perfectly spaced I'm goingo to dismount for check.

 

[Zen Mod]

then mount big washers and split washers

important when thermal cycling is present

 

[Morenmgu]

I check all weldings and seems right.
When I turn on the power amp the Offset are in 0 but start to decrease to negative polarity While warming in 1 minute go to -1.9volts when I turn off the power amp, the Offset measure change polarity and go to 0 again..... the Offset resistor seems Works well because I can adjust it to 0 again, but are continously decreasing when is warming....

R18 - 0.39V R - 19 - 0.42V R - 16 - 0.41 R - 17 - 0.41V

 

[Morenmgu]

After turn crazy, and compare both pcb's, I think the problem can be from LSJ 74, what do you think ? Because without any rca conected R18-19-16-17 in the right chanel I measure 0 volts so.it's ok but on the ring chanel left, I measure 0.4v more or less in all resistors....

I think have sense.

 

[Zen Mod]

voltage across D1?

 

[Morenmgu]

8.9volts....

 

[Zen Mod]

R30,R6,R8,R8',R7,R7'

what you have and what you don't have?

 

[Morenmgu]

R30 Bridged
R6 Bridged
R8 resistor RN60D 1001F
R8' where ?
R7 2K Trim pot
R7' where ?

 

[Zen Mod]

measure voltage across R8 and confirm it is 1K, as on schematic