Low output on Partridge output transformer

[Sansteeth]

Hey everyone,
I just built a new 100W amp, loosely based on the Laney Supergroup (4x EL34). My customer supplied the Partridge transformers (power and output).
The problem I'm having is that at 400Hz on my signal generator, I'm getting around 40W before clipping at 8 ohms (P = V²/R so 17.95²/8 = 40.27W)  but I am getting 115W at 4 ohm though (21.5²/4 = 115W which looks more realistic). I couldn't check the 16 ohm tap as my dummy load is only 4 and 8 ohm.
I checked again the impedance ratio on each winding in case I messed something up in the building process. I calculated the impedance ratio by inputing 10VAC into the primary. Which gave me:
GREEN:      10.09VAC (pri) -> 0.48VAC (sec)   21.02 turn ratio / 441.87 Impedance ratio
YELLOW:                               0.68VAC            14.84                  220
RED:                                     0.96VAC            10.51                  110
The partridge was taken from a 100W / 4x EL34 amplifier so we can assume a primary impedance around 1900 ohms so not only everything computes (sec impedance = pri impedance / impedance ratio - > 1900/441 = 4.3, 1900/220= 8.6, 1900/110 = 17.3) , but the separate winding must be working okay if I could measure their impedance ratio (no shorting, no break in the winding).
However, my hypothesis is still that the part of the winding between ground and the 4 ohm tap is fine, but that after that, something is wrong. I just cannot figure out what else might be the problem or what else should I check at this point.
Any leads, piece of advice is welcome!

Thanks a lot

[PRR]

Have you verified your dummy load with an ohmmeter? If it has been overheated, or mis-labeled, it may not still be what it says.

[Sansteeth]

Bingo! 
My impedance switch was flaky, I was getting 4 ohm load on both. Getting a healthy 110W before clipping now on the 8 ohm tap.
Thanks a lot, I shouldn't trust my test equipment so easily!