1073's one chanel is 10db down?

[focal6]

Hi All,

Just finished two EZ1073 units which went well, both units are working.

However, a stereo test quickly showed an approximate 10db variation between the units on line inputs. Mic pre is returning the same signal gain.

With a -12db test tone, the first unit returns a -12db signal which is great. The second unit is returning -22.

I've tested all cables and various inputs/outputs on my Apogee Ensemble but all render the same result; second unit is 10db down.

Pulled the unit in question out and checked all solder points and work. Double checked the calibration as recommended in the build instructions on both units and all is as it should be.

Does anyone have any ideas what could be causing this?  Is there any further point values I can be checking to narrow down my fault?

Any advice from you kind folk with more knowledge than I would be much appreciated.

Thanks in advance.
Rosko

 

[focal6]

Doing my best to work this out myself. Looking at the circuit diagram and knowing the Mic pre is operating with equal gain on both units, would I be correct in assuming the issue must exists somewhere in the input gain circuit?  Both the mic input and line inputs share gain stage 2 and the output stage circuit, so if the problem were in the gain stage it would be present on both mic and line. Correct?

 

[API]

Did you check your Line input transformer wiring and that you bridged the correct pins?

 

[focal6]

API.... You Nailed it!!!! 

Thank you very much!!!! 

 

[API]

There you go!
Happy that i could help.

 

[focal6]

OK, API I hope you're still around? 

You correctly identified my error in transposing the cards on the input transformers which has the pin bridging on them, thank you again. I desoldered the boards and corrected the board locations line inputs now match between my two units.  However.....

Now the mic input is behaving as though the mic is not getting 48v Phantom power (very low volume).  After some testing it most definitely is outputting the 48v on pin 2. Toggling the switch shows the 48v is present when switch is engaged.

Any ideas what could be causing this?