Early Sand Cast UTC LS-12X Wiring Different?

[emrr]

If you have visible wires coming through the terminals and they are soldered, pulling them out further ain't gonna make them 'mo-betta' soldered. 

Make us a list of your DCR's for all connections. 

 

[MrG]

If you have visible wires coming through the terminals and they are soldered, pulling them out further ain't gonna make them 'mo-betta' soldered. 

Make us a list of your DCR's for all connections.

Thanks, Doug - will do. I don’t question your expertise, but I do want to clarify that some of these wires did not look particularly well soldered, and weren’t pulled up through very far. Some looked like cold joints, some looked slightly gunked up and a bit oxidized. At the moment, I’m not able to get DCR readings between all of the terminals.

I’ll do a thorough cleaning and then try again to get readings. Should there be DCR between every terminal?

Thanks,
Mark

 

[emrr]

There should be DCR matching the paths on the schematic drawing, in catalog or from a picture of a 1970's example.  There should not be DCR between terminals that aren't connected on the drawing.  Nor to ground from any terminal other than ground. 

 

[MrG]

Ah ok, makes perfect sense. Thank you very much.

Mark

 

[MrG]

Hey all,

Finally got the materials and time to work on this tonight. I desoldered each terminal thoroughly, applied deoxit gold g100, wirebrushed all terminals, applied made in us amtech no clean flux, and then applied solder to each terminal. I was able to see good amounts of wire in every terminal hole, only slightly weak on Pin 3 & 7.

Upon testing, I did not get DCR readings between anything and Pin 3, and I got no secondary DCR readings at all... Very upsetting.

Any ideas of what to do next would be much appreciated. @CJ do you think you could get useful info from this and also potentially fix it?

Thanks again in advance,
Mark

 

[dmp]

If pin 3 is disconnected from the coil it might take surgery to fix it.  It can be pretty difficult to fix a lead that is broken from the coil.

To use it as-is, hook it up without using pin 3: connect to 1 & 6 and join 2 and 5. It will be a higher ratio.
To reduce the ratio hook the secondary up in parallel (join 7&8, 9&10) instead of series.  you could try it both ways and see what you like.

 

[MrG]

Thanks, dmp. But is it normal that I got no secondary readings? Are they too small for my meter or something?

 

[dmp]

Thanks, dmp. But is it normal that I got no secondary readings? Are they too small for my meter or something?

Are you measuring the resistance between  7 & 10 or 7&9 and 8&10?
7&10 should be inf unless 8&9 and tied, but 7&9 and 8&10 should both be a measurable ohms. If you have multiple scales on your meter flip through them.

 

[MrG]

Are you measuring the resistance between  7 & 10 or 7&9 and 8&10?
7&10 should be inf unless 8&9 and tied, but 7&9 and 8&10 should both be a measurable ohms. If you have multiple scales on your meter flip through them.

I get nothing on 7 & 9 or 8 & 10... such a bummer. How can these wires look healthy on the outside but somehow get broken on the inside?

 

[dmp]

Who knows what wrecked it.
The secondaries should have given you about 2k-3k ohms I'd guess.
The wires inside on the winding are much finer and more delicate. They are usually soldered to heavier duty wires inside and taped. The heavier wires come out to the terminals. It could have been hooked up with too much power going through it or mechanical damage somehow. I once was able to peel back the tape on a transformer and find a broken wire and reattach it to heavier wire coming out, but it is difficult. It could also be fried inside the coil which would make it impossible to fix. You have to get the thing disassembled first, which is hard to do non-destructively. I think you need to heat it which is going to be real toxic so don't try it at home

 

[CJ]

check your ohm meter on a 1 k resistor to make sure it works.

do you have a power supply? try injecting 5 volts into the secondary wires with an ammeter in series, use 9 volt batt if no supply. do you see any current?

unfortunately, those transformers are very hard to rewind as the use two pies of thin wire wound side by side, and with foldback winding, (the wire is brought back all the way to the start with a turn or two) 

may as well take it apart, you might see something wrong where the leads join the windings and be able to fix it.

sorry for the bad news,  :

 

[emrr]

70+ years of humidity ingress, large temp changes causing expansion/contraction, corrosion, etc.  All can kill a transformer.