"WHAMMY" Pass DIY headphone amp guide

I feel terrible because I am not sure how to do that either, could you explain it to me? (how to check the output of the transformer)
Don't feel bad! I edited it after you posted, because it was unclear: Check at the input to D1/D2 and D3/D4, which is the side near the transformer. Then I'd check the output voltage, too, on the other side of the diodes. Note that the transformer output is an AC voltage. So (I think) is what's coming out of the diodes, though it is a funny looking wave.
 
@1nfinity

With your DMM set to DC volts, 200V if not autoranging,

put the black lead on ground, the input wire’s shielding near the pot is a decent spot,

then with the red probe,

tell us the voltage at the line side (cathode) of D7

and the not line (anode) side of D8.




This will measure the unregulated PSU.
 
@1nfinity

With your DMM set to DC volts, 200V if not autoranging,

put the black lead on ground, the input wire’s shielding near the pot is a decent spot,

then with the red probe,

tell us the voltage at the line side (cathode) of D7

and the not line (anode) side of D8.




This will measure the unregulated PSU.
It gave me -0.34. leaving it unplugged (turned off), correct?
 

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I think it would be good to take some in focus close up views of the bottom of the board. Seems like you could have some possible cold solder joints just looking at the top pics. I guess if it was working for a while, then it's unlikely a solder joint gave way.

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Don't feel bad! I edited it after you posted, because it was unclear: Check at the input to D1/D2 and D3/D4, which is the side near the transformer. Then I'd check the output voltage, too, on the other side of the diodes. Note that the transformer output is an AC voltage. So (I think) is what's coming out of the diodes, though it is a funny looking wave.
So I did this and the only thing that's getting anything is D2. Away I am getting D1 at 4.76 and D4 4.14