High output levels from 2 T15 Rev. 1.5 Builds

[samth3mancgp]

I finished up building two T15 kits a few days ago and I was getting much much hotter signal level out of the new builds than both of my older T15 builds and my A12. Does the SW1 have to be in a certain position before putting the stop pin in? That was something that confused me that may be a problem?

I will be headed down to the studio in a bit and I will try to provide more info and maybe even some pictures of what I was seeing on the scope.

I also noticed that the Sine wave didn't look as clear with the polarity reverse engaged.

-Sam

[samth3mancgp]

Alright so after much screwing around with my scope, signal generators and meters I think I figured it out.. Everything seems to be fine. all 4 of my T15s (two are Rev. 1.3 boards that I put together in my dorm room freshman year with no meter, no scope, no useful test rigs at all.

I was testing by sending a low level signal (about 16 mV) into just the hot input. That must have been my biggest issue from the start. The earlier T15 builds were reading way lower output than the new ones, and they were showing all kinds of noise and crap too. Then I used both channels of my scope to measure the hot and cold OUTPUTS by flipping polarity of the cold and putting the two channels in "add" mode.

Last thing I did was instead of sending signal in only on the hot pin 2.. I ran the signal generator through a DI box so that the signal generator was pushing out a balanced signal. That seems to have eradicated many of my odd measurements.. Both T15s are reading 25V P-P with the gain at 8 clicks up.. Over 40V P-P at 9 clicks and after that it clips. The A12 actually seems to have about 5dB less gain at gain position 8 than the T15s?

Only thing that I see now is that the newly built T15s have a slightly "fuzzier" looking waveform than the other T15s or the A12 has. I did decide to put the inductors in at L3 and L4 because they are present in the Rev. 1.5 schematic. The Rev. 1.3 T15s have jumpers installed at L3 and L4, but the L3/L4 spots are on a different place on the board. There appears to be caps in the place where the inductors are on the new builds. There is a significant amount of confusion in the assembly instructions. Seems like they are still for the Rev. 1.3 board. The 1.5 has some components that are gone, and others that are added.

If anybody reads this (Tim, where are you? ) I'd love to get some feedback on the tests that I ran. I have some pictures of my final scope readings (the "fuzzy" T15 waveform, and the A12 being quieter.) Hopefully I can get those things cleared up!

-Sam

[samth3mancgp]

Another update...

It seems that after putting the front panel on and re-assembling the chassis that the newest T15 builds are showing a nice and clean sine wave on the scope! It must have been an interference problem or something from me doing tests with the chassis open. The magnifying work bench lamp that I use has a fluorescent bulb in it and it makes the scope show weird things sometimes..

I'm still curious about L3/L4 in the different revisions of T15 builds, as well as why my A12 may be 5dB lower than the T15s at the same gain knob level (8 clicks up).

-Sam