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!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

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.

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #9 on: October 17, 2018, 09:48:51 PM »
Hello all,

Apologies for the delayed response and thank you all for your input.

I was able to test the LS-12Xs last night and noticed a few things:

-some of the wires which come up from the transformer core into the terminals look like they are not totally soldered to the terminals. I flowed solder into the holes and onto them - is this recommended?

-I was getting DCR for most terminal connections, but not all. Some of them only when I moved my multimeter pin probe around to somewhat odd locations on the terminal. Do you all always use alligator clips to make sure you’re connected or is using probes ok?

-It seems perhaps one wire was damaged in my previous test on one of these. I’m going to resolder them and check again.

So, the looming, sh*tty question is... what if one or both of these gorgeous transformers is broken. @CJ, do I send to you to analyze and do you fix transformers like these? Fingers crossed.


Thanks all,
Mark


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


EmRR

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #10 on: October 18, 2018, 07:38:10 AM »
Not uncommon for terminals to be so tarnished/corroded that you don't get readings.  Heat all and reflow the solder. 
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

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #11 on: October 20, 2018, 10:05:52 PM »
Not uncommon for terminals to be so tarnished/corroded that you don't get readings.  Heat all and reflow the solder.

Thanks, Doug. That makes sense. Thing is, in this case, it is fairly clean, however just looks like the inner transformer wire is not solidly connected to the terminals.

My more specific questions are relating to how to properly rehab/restore a nice, fairly clean, but very old transformer:

-should I strip them of as much old solder as possible, using braid of solder sucker?

-when flowing new or reflowing old solder, is there a concept of letting too much solder go down the terminal hole into the inside of the transformer? (I ask because some of the terminals don’t appear to “fill up”)

-If my meter perhaps still does not show DCR on some pins, is it possible that the exterior of the pins are just too dirty for a meter reading, but they will still pass signal when electrically connected?

Thanks so much for all of your input.

Mark

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

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #12 on: October 21, 2018, 12:47:50 AM »
I've soldered to the tabs of old LS transformers with dodgy terminals before, and you want to minimize the total heat. If you savage the terminal with a ton of heat, eventually tar will ooze out of the hole in the center of the terminal. (I was a careless youth when I learned this, about 35 years ago - passing this along so you don't have to go there either!)

The best idea might be to gently use a wire brush and some ProGold to cut away the years of oxide buildup, then wipe off the ProGold, apply a little no-clean flux, and then re-solder each terminal. If you can't get it shiny and nice easily, use the brush again to prep the metal, re-flux it, and then try again when everything's cooled down. The soldering iron tip should have enough thermal mass and be set to a high enough temperature so that you don't have to spend much time tinning the terminal and the winding. But again, don't set it to stupidly high temperatures , which I would imagine would be over 750ºF. 700ºF should be enough if the tip has enough mass and the metal is clean.

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #13 on: October 21, 2018, 10:49:49 PM »
I've soldered to the tabs of old LS transformers with dodgy terminals before, and you want to minimize the total heat. If you savage the terminal with a ton of heat, eventually tar will ooze out of the hole in the center of the terminal. (I was a careless youth when I learned this, about 35 years ago - passing this along so you don't have to go there either!)

The best idea might be to gently use a wire brush and some ProGold to cut away the years of oxide buildup, then wipe off the ProGold, apply a little no-clean flux, and then re-solder each terminal. If you can't get it shiny and nice easily, use the brush again to prep the metal, re-flux it, and then try again when everything's cooled down. The soldering iron tip should have enough thermal mass and be set to a high enough temperature so that you don't have to spend much time tinning the terminal and the winding. But again, don't set it to stupidly high temperatures , which I would imagine would be over 750ºF. 700ºF should be enough if the tip has enough mass and the metal is clean.

Thanks for this tip, Monte. I will try this cleaning. I did see a little bit of bubbling occur, but it seemed more like nasty old dust/grime than tar. Could I have damaged the transformer if this was the tar you’re speaking of?

I hear you about soldering. I use a Metcal and don’t overheat or prolong heat, as a rule. In this case, I may have slightly due to continuing to feed solder into the terminal hole.

Mark

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

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #14 on: October 22, 2018, 01:12:58 AM »
Thanks for this tip, Monte. I will try this cleaning. I did see a little bit of bubbling occur, but it seemed more like nasty old dust/grime than tar. Could I have damaged the transformer if this was the tar you’re speaking of?
Probably no damage,  but releasing the inner potting compound will only gunk up the terminals further, and can't be a good idea. I just wanted to pass along my newbie experience from decades ago so you don't have to follow in those footsteps! :)

Quote
I hear you about soldering. I use a Metcal and don’t overheat or prolong heat, as a rule. In this case, I may have slightly due to continuing to feed solder into the terminal hole.
Glad to hear you have proper soldering tools and such - one never knows what folks are using! I don't think there's any need to feed solder into the terminal hole, but as you're making the final connection, it's probably not a bad thing to see that solder seals the entire terminal, just to keep the transformer sealed. However, you'll add your own connection wire to the terminal that will cover the hole anyway, so if you just make sure the final solder fillet covers the terminal, the internal transformer wire, and your final connection, it should be perfect.

For now, all you need to do is clean up the terminal and the internal transformer wire, and make sure that everything flows. The hole can remain open for now, until the final installation.

CJ

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #15 on: October 22, 2018, 02:16:19 AM »
at the UTC factory the leads were brought up through the terminals, wrapped around the terminals and soldered.  sometimes people will suck all the old solder off the terminals in order to solder new leads to their equipment. if they mistakenly think that the wrapped wire is somebody else's wiring job, they will remove the wrap. noiw if you resolder, the wire is free to fall back inside the can.

the fix for this is to pop the  plate off by taking about a 3/8" drill bit and carefully drilling away the  outside diameter of the rivets that hold that lid on. you have to be gentle or else the bakelite/phenolic plate will snap as it is very brittle.

there is usually a void in the potting compound right under the lid so after you remove the metal that is holding the lid down,  you can usually lift it up about an inch, which is enough to spot leads that have worked loose from the terminals.  so you then clean the terminal and resolder the wire and you are done.




If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #16 on: October 22, 2018, 09:30:06 PM »
Probably no damage,  but releasing the inner potting compound will only gunk up the terminals further, and can't be a good idea. I just wanted to pass along my newbie experience from decades ago so you don't have to follow in those footsteps! :)
Glad to hear you have proper soldering tools and such - one never knows what folks are using! I don't think there's any need to feed solder into the terminal hole, but as you're making the final connection, it's probably not a bad thing to see that solder seals the entire terminal, just to keep the transformer sealed. However, you'll add your own connection wire to the terminal that will cover the hole anyway, so if you just make sure the final solder fillet covers the terminal, the internal transformer wire, and your final connection, it should be perfect.

For now, all you need to do is clean up the terminal and the internal transformer wire, and make sure that everything flows. The hole can remain open for now, until the final installation.

Thanks for the follow up! Looking forward to getting this done.

at the UTC factory the leads were brought up through the terminals, wrapped around the terminals and soldered.  sometimes people will suck all the old solder off the terminals in order to solder new leads to their equipment. if they mistakenly think that the wrapped wire is somebody else's wiring job, they will remove the wrap. noiw if you resolder, the wire is free to fall back inside the can.

the fix for this is to pop the  plate off by taking about a 3/8" drill bit and carefully drilling away the  outside diameter of the rivets that hold that lid on. you have to be gentle or else the bakelite/phenolic plate will snap as it is very brittle.

there is usually a void in the potting compound right under the lid so after you remove the metal that is holding the lid down,  you can usually lift it up about an inch, which is enough to spot leads that have worked loose from the terminals.  so you then clean the terminal and resolder the wire and you are done.


Thank you very much, CJ - this is great to know. Sounds nerve-racking,  but better than trashing this transformer. If the plate breaks, am I screwed? Or is it just a matter of it looks bad? Also, how do you re-affix the plate?

Thanks,
Mark

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

CJ

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #17 on: October 23, 2018, 01:25:12 AM »
dang, i got mixed up between the HA series vs LS series,  :o

you probably have the circular plate,

you could try and heat up the top half of the transformer with a heat gun and try to pry the lid off,

here is what it looks like on the inside>

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

EmRR

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #18 on: October 23, 2018, 09:45:48 AM »
I've been assuming the rectangular-ish plate and non-circular pin layout.  Those are held in place with 4 corner pins/nails/tacks that should pry out.  If they're gone, it's evidence it's probably already been tampered with.  Those are easier to open than the later circular types. 
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

MrG

Re: Early Sand Cast UTC LS-12X Wiring Different?
« Reply #19 on: October 24, 2018, 05:13:51 PM »
I've been assuming the rectangular-ish plate and non-circular pin layout.  Those are held in place with 4 corner pins/nails/tacks that should pry out.  If they're gone, it's evidence it's probably already been tampered with.  Those are easier to open than the later circular types.

You’re correct - it’s non-circular, with rusty tacks. They don’t look tampered with, but they do look like I could easily remove them.

I tried to reflow and resolder (without cleaning with Pro Gold, which is in the mail), and again only passing very low signal. I’m going to try cleaning thoroughly, but I’m a bit afraid I’ll need to break these open if I want to salvage them.

Question:
-if I clean and desolder with braid, is it reasonable to consider using tweezers to pull the wires through more? Or could this damage?

Thanks,
Mark

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


 

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