LO1166 issue in 1272

[Golgoth]

Hi,

I am having an issue with an LO1166 transformer I am installing in a 1272 module I am restoring.

The output has absolutely no bass. I tried without the zobel components, same thing.
The rest of the module is working well up until pin 1 of the LO1166, but pin 5 & 8 output no bass, the transformer basically acts as an HPF (pin 5 is louder than pin 8 if that is useful info).

What can I test/measure to make sure the transformer is okay? It was provided to me untested by a client.

Best,
G

 

[Khron]

pin 5 is louder than pin 8 if that is useful info

In relation to what, exactly?

 

[Golgoth]

In relation to what, exactly?

Pin V on the back connector

 

[Golgoth]

I wonder what you think about it Ian @ruffrecords

 

[ruffrecords]

How did you set the quiescent current in the 2N3055? Sounds like the core might be saturating.

Cheers

Ian

 

[Golgoth]

How did you set the quiescent current in the 2N3055? Sounds like the core might be saturating.

Cheers

Ian

Thanks for chiming in Ian, I provided a 1K sinewave at +20dbu and set RV1 for 4.7V across R7

 

[ruffrecords]

Thanks for chiming in Ian, I provided a 1K sinewave at +20dbu and set RV1 for 4.7V across R7

That looks a little on the high side to me. Try setting it to 3.3V.

Cheers

Ian

 

[radardoug]

Your wiring is probably wrong, and you dont have both ends of the primary or secondary wired correctly.

 

[Golgoth]

That looks a little on the high side to me. Try setting it to 3.3V.

Cheers

Ian

Will try and report back!

 

[Golgoth]

Your wiring is probably wrong, and you dont have both ends of the primary or secondary wired correctly.

Pin 2 & 4 linked
Pin 6 & 7 linked
Pin 1 to BA283 card pin B
Pin 3 to BA283 card pin M
Pin 8 to rear connector pin R
Pin 5 to rear connector pin T

 

[ruffrecords]

Pin 2 & 4 linked
Pin 6 & 7 linked
Pin 1 to BA283 card Pin B
Pin 3 to BA283 card Pin M
Pin 8 to back connector Pin R
Pin 5 to back connector Pin T

And you have J linked to A?

Cheers

Ian

 

[CJ]

Is it an original? Check continuity.

 

[Golgoth]

And you have J linked to A?

Cheers

Ian

Absolutely, A-J-V are linked

 

[Golgoth]

Is it an original? Check continuity.

Hi CJ, continuity is fine per the transformer's datasheet. It is an original Marinair.

 

[Golgoth]

That looks a little on the high side to me. Try setting it to 3.3V.

Cheers

Ian

No improvement at 3.3V unfortunately, no luck either when swapping for another working BA283 card..

 

[Khron]

And what're you plugging the output of the transformer / preamp into, that results in "no bass"?

Photos of the connections could potentially help... But i'm starting to wonder if, by some freak occurrence, one of the four windings ended up being connected in reverse, somehow?

 

[Golgoth]

And what're you plugging the output of the transformer / preamp into, that results in "no bass"?

Same result with an audio probe and in my 1272 rack.

 

[Khron]

Same result with an audio probe and in my 1272 rack.

"With an audio probe"? (Those are rarely balanced-input, but i stand to be corrected...)

And "in my 1272 rack" is not an answer to "what is the output of your 1272 plugged into?" question. Because logic / physics...

 

[CJ]

here is a print for checking things out like DCR etc

there is a reverse wind on the original that the later versions did not have but that should no affect the terminal assignments but you could try swapping them anyway,

that xfmr did not have a ton of inductance to begin with, steel core, not that many turns, maybe something other than the circuit like test leads, test equipment, etc,

i doubt the gap has increased as those are glued together pretty good.