Aleph 5 with no (few) gain

[ElectroNick]

Hi,

The past week i've been testing the A5 amp. One channel gives 16 mV at output at works fine.
But.... the other one seems to have no gain. While inspecting both channels i found that at the base of Q5 (T4 in the Kristian schematic) there was a lot of noise on the signal. The signal itself is not amplified, in the other, good mono section you can see a larger signal.

The only thing i recall the past week, while switching between both channels., i heard some "spikes" while connecting the speaker to the bad amp.

So far i changed C10 and Q5 (T4 and C3 in the Kristian schematic)

What can it be, i'm getting confused. Am i looking in the wrong place, i mean is some other component responsible for the trash signal on the base of Q5 ?

 

[Phill]

hello


I am sorry to be able to answer your question ...

I visited your Web page ...

can you explain this image

An externally hosted image should be here but it was not working when we last tested it.

which are the components used?
thank you
Phill

 

[Netlist]

Does the diff pair work?
What DC values do you get at the crucial points? VCE Q5, voltage over R14, is there bias current flowing trough the outputs?

/Hugo

 

[ElectroNick]

I found the error

It seems that i drilled through a trace when i was placing the three capacitors, they had a different size.
I soldered the caps but overlooked the missing trace

Anyway : a simple repair on the PCB and the Aleph was working.
I'm now building it together again and in an hour or so i'll sit back and relax (maybe with some wine )

Grtz
Nick


ps : @ Phil
It's a simple discrete rectifier with MBR1645 and some MKS caps.

ps2 : i'm not using this bridge at the moment, for now only a "simple" metall rectifier bridge.

 

[Netlist]

/Hugo