Aleph 5 problem 2

[Bill Fuss]

I dont know what preamp or CD player you have but you dont have any signal at the input. You want at least .5V of signal to do any checking. If you cant get a decently large signal at the rca the amp isn't the problem.

 

[pmchoong]

Maybe I should turn the volume up. I did the measurement on the good channel.

 

[pmchoong]

a rega planet player and a classe dr6 pre

 

[Bill Fuss]

What are you using for Q4-5.

 

[pmchoong]

BC550

 

[Bill Fuss]

Did you get the pinouts from the data sheet, they are different than MPSA18.

 

[pmchoong]

If I turn the volume up, I can't get a steady number. The numbers just go bigger between 0.015 - 0.80v. I forgot to remove the xlr from the slot and now there's a slight buzzing sound on the speaker of the good channel. Sorry, I was taking measurement on the bad channel with the xlr input as the RCA input causes the speaker cone to move rapidly. (I measured the amp with the speaker unplug cause I worry it may damage the amp with the RCA plug in)

 

[pmchoong]

The CBE is reverse as oppose to the MPSA18. But I put them in correctly onto the board.

 

[pmchoong]

I think I'll just use the xlr and forget about the RCA, it is better sounding than the RCA. What do you think?

 

[Bill Fuss]

You're not going to get a steady number, you're looking at the signal itself, and it is constantly changing.

Ok, now if you go to Q4 collecter you should get a larger varying number.

 

[pmchoong]

Why is it that I got 0 ? Both amps?

 

[Bill Fuss]

Well, basically that's impossible if the amp works, thats the only path to the output fets. Check your meter.

 

[pmchoong]

When I turn on the volume up and put my ear close to the amp, I can actually hear the amp singing, faintly. i turn the DMM to auto with the AC sign appearing.

 

[pmchoong]

I put the negative probe onto the star ground and measure the collector with the positive probe

 

[Bill Fuss]

And you have the DMM hooked up between the collecter of Q4 and ground and you get no reading?

 

[pmchoong]

Thats right

 

[Bill Fuss]

And you get the same on the good channel, then your meter is at fault.

 

[pmchoong]

am i doing something wrong here?

 

[Bill Fuss]

I don't know, I can't tell from here.

 

[pmchoong]

Actually, the number goes up to 2.xx before returning to 0.00