MrG

Early Sand Cast UTC LS-12X Wiring Different?
« on: October 11, 2018, 10:33:56 PM »
Hey all,

I’m attempting to wire up two LS-12Xs that are both very early black sand cast examples, one is Patent Pending. Both of them are presenting different but similar issues: no output, or very low output. I am wiring them identically to my LS-10 and LS-10X, as the documentation I have says is appropriate, but still, no dice.

Anyone here know something I don’t about these early models’ wiring?

Thanks much in advance,
Mark

Mark Galup | Producer/Mixer/Mastering Engineer
ReelRecording.com
MarkGalup.com


radardoug

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #1 on: October 12, 2018, 01:41:51 AM »
You need to use an ohmeter to figure out what windings are on what pins, and if you have missing windings. Then you can apply signal and see what comes out where at what level

scott2000

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #2 on: October 12, 2018, 04:32:32 AM »
I attached some info in case it helps anyone . Let me know if it's incorrect MrG.

dmp

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #3 on: October 12, 2018, 03:21:31 PM »
The hook up is the same between a LS-10 and LS-12 but the LS-10 is 600:60k while the LS-12 is 600:120k, so if you are wiring them the same way, the LS-12 will have more voltage change than the LS-12. LS-10 is 10:1 and LS-12 is 14:1
If you ran a signal into both secondaries and measured the output (step down) at the primary the LS-10 would be -20 dB while the LS-12 would be -23 dB
 
Wiring should be:
primary:
600 ohm: 1 &6, tie 3&4
300 ohm: 2 & 5, tie 3&4

secondary:
7 & 10, tie 8&9

but if you want to halve the LS-12 to get the same turns ratio as the LS-10, you could try putting the secondaries in parallel:
7,8 & 9,10

This would get the same voltage ratio as a LS-10 I think

I have several old UTC catalogs that have hookup info in them so I don't think there was any difference between the eras

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #4 on: October 13, 2018, 12:34:11 AM »
Hey all,

Thank you very much for the input. I can confirm my documentation sheet (from inside an old UTC box) has these same pin diagrams and ratings. Still no luck as of yet but I’m going to dig further.

A few thoughts/questions:

You need to use an ohmeter to figure out what windings are on what pins, and if you have missing windings. Then you can apply signal and see what comes out where at what level

I have thought to do this. Can anyone tell me how to set up my multimeter to be able to measure the actual impedance? Forgive me if this is obvious.

Here’s something strange: when I hook up this trafo as a DI, the bass signal is crazy low compared to how it should be, but it’s there. When I touch the open cable connected to the trafo while it’s plugged into my DAW, the level/volume of my finger touching the jack (you know the sound of touching a cable plugged into a guitar amp), is very loud, as if the impending guitar/bass volume will be very loud,  but then it is super low once I plug it in. Probably -40-50dB.

ALSO, I just hooked up a pair of UTC LS-30s in series with some other matching trafos I have, and only once they were plugged in, one of the other pairs (of custom Hammond 804s) started exhibiting the same behavior - a super low output around -50dB.

So, am I missing some theory here?


Thanks much in advance!
Mark

Mark Galup | Producer/Mixer/Mastering Engineer
ReelRecording.com
MarkGalup.com

radardoug

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #5 on: October 13, 2018, 01:00:49 AM »
You cant measure the impedance with a multimeter, only the d.c. resistance. But that is very helpfull in making sure you dont have an open circuit winding. From the sound of your experiments, you have a miswire or an open circuit.

CJ

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #6 on: October 13, 2018, 01:47:33 AM »
don't have the UTC 12 specs but i bet they are close to the A-10 specs,   LS-10 and 10X is just an A-10 nested inside a bunch of cans for low noise,   

measure the primary DCR and compare it with this>

If I can't fix it, I can fix it so nobody else can!
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EmRR

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #7 on: October 13, 2018, 08:15:13 AM »
You’re mixing it up CJ, LS has larger core, different DCR readings.  You’ve shown us this in the past.  A and HA look more alike. 
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

PRR

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #8 on: October 13, 2018, 05:06:57 PM »
> how to set up my multimeter to be able to measure the actual impedance?

No. And why?

Use your plain Ohms range and look for DCR values from a few to a few-k, similar to CJ's table for a sorta-similar transformer.

Most likely bad-answer is a "winding" shows "infinite" DCR--- it is broken. That won't induce audio.

 

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