Aleph 5 problem 2

[Bill Fuss]

How about some pictures. You can use my email, I sent you one this morning.

 

[Bill Fuss]

That's more like it, now check the output, just leave the ground hooked up and take the reading from the plus binding post.

 

[pmchoong]

It goes something like 2.xxx to 3.xxx while the good amp goes from 17.xxx to 19.xxx

 

[Bill Fuss]

Do both channels read approximately the same at Q4 collecter.

 

[pmchoong]

I have notice that the bad channel doesn't go up to 10.xxx while the good one range from 1.xxx to 17.xxx

 

[pmchoong]

Do both channels read approximately the same at Q4 collecter.

The numbers appeared too fast but from what i see, there are very identical numbers, goes from 8.xx to 0.3xx then to 0.000

 

[Bill Fuss]

I would shut everything off and pull the board. Check all the solder joints and replace Q4 and 5. Not being there it's tough for me to suggest anything else at this point.

 

[pmchoong]

For both the amps?

 

[Bill Fuss]

No, just the bad one, assuming the other one sounds fine. It wouldn't hurt to check all the resister values too.

 

[pmchoong]

Thanks for the email. I just replied you. Ok, I will pull out the board. You suspected bad solder joints and bad Q 4 and 5?

 

[pmchoong]

The other good channel sounds fine with the xlr but not any more with the RCA. There's a slight buzz hissing sound when hook up the speaker.

 

[pmchoong]

Power connection

Please look at image 'earth connection'. On the right is how i hook up the connection from top down :

1) cold (black)
2) gnd wire (green) is connected to star gnd
3) gnd wire from chassis (connected from IEC)
4) transformer gnd (on left) and gnd wire connected to star gnd
5) Live wire (on right) from IEC
6) Live wire from transformer

Item 2 and 3 is connected by the CL40 thermister
Item 5 and 6 is connected by the CL60 thermister

 

[pmchoong]

Before soldering in XLR and RCA and closing of the back panel.

 

[pmchoong]

The inductor was placed at the bottom of the chassis

 

[pmchoong]

PCB is on top of PSU

 

[pmchoong]

Star ground, the green wire from left to right

1) from chassis
2) from transformer
3) to speaker negative post

 

[pmchoong]

PSU bus

 

[pmchoong]

70 degree thermistor and chassis gnd at bottom. Background is a fet mounted on a heat sink. Can anyone tell me why do i get a static noise when i play a CD on the amp?

 

[pmchoong]

Done.

Thanks to Nelson for your generosity, to Mark Finnis for your pcb design and to Bill for your help and for not giving up. Thanks to everyone who helped.