[mcluxun]

Power supply problem
I got +12.54 from the + side and -15.56 from the - side.
Is there any test point I could measure to debug the problem?

 

[shipsupt]

Sounds like something on the + side only, the - voltage seems about right.
 
I had some voltage questions when I was building the power supply, Craigs directions:
Check the voltage drop across the series resistor to the zener to see if the Zener is working. Then measure the voltage at the zener. The output from the transistor emitter should be .6 volts less than the zener voltage.

 

[holland]

^
 
You probably have a 14V zener installed.
 
1) Also check the voltage at the top of the big cap, just after the rectifier/bridge.  You should measure over 16V, and under 25V.  It should be around 20-22V with a 15VAC transformer.
2) Measure the voltage drop across the 1ohm resistor.  If the drop is disproportionately large, compared to the negative rail, you have something wrong in your amplifier build and it's pulling lots of current.  I would be surprised if something didn't fry if this is the case.
3) If you remove the amp from the PSU, you should have similar voltages on the positive and negative rail.
4) If that's all OK, the zener voltage drop is OK, then the transistor in the PSU is likely borked.  Make sure it's installed correctly.

 

[amcananey]

I just checked my copy of "The Art of Electronics"...I can't seem to find "borked" in the glossary....Can you provide a technical definition?

 

[kevin gilmore]

see Swedish chef.

 

[holland]

Quote:

I just checked my copy of "The Art of Electronics"...I can't seem to find "borked" in the glossary....Can you provide a technical definition?

 
It's in the unreleased 10th edition.
 
But, I can provide a visual definition.
 
http://youtu.be/br2s0xJyFEM

 

[shipsupt]

That's nothing like an Icelandic Baker, right?

 
Quote:

see Swedish chef.

 

[DefQon]

Quote:

That's nothing like an  Viking Baker, right?

 

Fixed ~ 

 

[kevin gilmore]

Quote:

That's nothing like an Icelandic Baker, right?

 

not a muppet fan??

 

[shipsupt]

Actually he was one of my favorites!
 
And Animal on the drums of course.

 

[holland]

I liked Kermit and Fozzie.  Statler and Waldorf were up there too.  Waka waka!
 
BTW, since you're on the thread.  How do you like the amp?  It looks meh, but perhaps it sounds better than one would think.

 

[mcluxun]

Well
It looks like my R2 is borked.
I replaced R2.
Then the output on the + side is 32 something.
Ive got following measures
c6 15.36v
d2 15.87v
 
 
c5 32.04v
d1 32.07v
 
Is my d1 borked too?

 

[holland]

Quote:

Well
It looks like my R2 is borked.
I replaced R2.
Then the output on the + side is 32 something.
Ive got following measures
c6 15.36v
d2 15.87v
 
 
c5 32.04v
d1 32.07v
 
Is my d1 borked too?

 
Resistors don't normally fry, but it does look like d1 is borked now.  Double check that the transistor is working too.  There should be a 0.5V-1.0V drop from D1 to the part of R7 that points toward the transistor (or the output of the emitter).
 
Your DC voltage is awfully high.  What's the AC you're feeding it?  What size caps are in those positions?  According to the schematic and BOM, those are 25V caps.  You'll likely be replacing them soon.  25V is marginal there, as an unloaded 15V transformer can reach that limit, but 32V is way high.  Your AC is about 23V.  Is that transformer really 15VAC?

 

[mcluxun]

Quote:

 
Resistors don't normally fry, but it does look like d1 is borked now.  Double check that the transistor is working too.  There should be a 0.5V-1.0V drop from D1 to the part of R7 that points toward the transistor (or the output of the emitter).
 
Your DC voltage is awfully high.  What's the AC you're feeding it?  What size caps are in those positions?  According to the schematic and BOM, those are 25V caps.  You'll likely be replacing them soon.  25V is marginal there, as an unloaded 15V transformer can reach that limit, but 32V is way high.  Your AC is about 23V.  Is that transformer really 15VAC?

R2 is fried for sure. It's charred and resistance is way greater than 100.
I used the transformer in the BOM it yields 35vac or 17vac.

 

[mcluxun]

Weird transformer problem.
I dont know if it's unlucky me or everyone else.
I bought the exact transformer according to BOM, wired as 30vac.
The output is 38Vac! And my home voltage is ~125Vac.
The first time I thought it's a defective product so I get another one free from mouser.
Guess what it's the same thing!! 38Vac.
Anyone else ran into this problem?