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OT: Stabilizing Old Transformer Input Wires

n4buq All Messages By This Member #182003 I just don't know where there's an appropriate group for this so thought I'd ask here. I have a transformer (out of a fairly old SOLA CVT) whose 115V input leads have become fragile right at the point where they enter the windings. It is good enough to get a wire spliced onto it but I would like to stabilize the point where it enters the transformer. This transformer was inside of a metal housing and poured with a generous layer of tar to stabilize everything - including the laminations as those can be noisy. While tar would probably work, I'd rather use something else and only at the point where these two wires enter the core to hopefully prevent further breakage after the splice is made. I'm thinking of making a small form at the end of the core around the wires and pour a potting compound of sorts in the form. My first thoughts would be something akin to silicone sealant but, as I understand it, that stuff is not kind to wiring. Roofing tar might work if it sets up firmly enough but, again, would like to steer clear of more tar. Is there something out there that would work well for this? Feel free to respond directly to me. Thanks, Barry - N4BUQ
Bruce Griffiths All Messages By This Member #182004 Neutral/alcohol cure silicone should be fine. Just avoid acetoxy cure grades. Two pot silicone should also be OK as long as curing doesnt produce amines or acetic acid. Bruce toggle quoted message Show quoted text On 28 April 2021 at 15:14 n4buq <n4buq@...> wrote: I just don't know where there's an appropriate group for this so thought I'd ask here. I have a transformer (out of a fairly old SOLA CVT) whose 115V input leads have become fragile right at the point where they enter the windings. It is good enough to get a wire spliced onto it but I would like to stabilize the point where it enters the transformer. This transformer was inside of a metal housing and poured with a generous layer of tar to stabilize everything - including the laminations as those can be noisy. While tar would probably work, I'd rather use something else and only at the point where these two wires enter the core to hopefully prevent further breakage after the splice is made. I'm thinking of making a small form at the end of the core around the wires and pour a potting compound of sorts in the form. My first thoughts would be something akin to silicone sealant but, as I understand it, that stuff is not kind to wiring. Roofing tar might work if it sets up firmly enough but, again, would like to steer clear of more tar. Is there something out there that would work well for this? Feel free to respond directly to me. Thanks, Barry - N4BUQ
Glenn Little All Messages By This Member #182005 Use RTV that is labeled oxygen sensor safe. The bad stuff cures and releases acetic acid. You can smell it when you open the tube. The good stuff cures with IIRC methyl alcohol. 73 Glenn WB4UIV toggle quoted message Show quoted text On 4/27/2021 11:14 PM, n4buq wrote: I just don't know where there's an appropriate group for this so thought I'd ask here. I have a transformer (out of a fairly old SOLA CVT) whose 115V input leads have become fragile right at the point where they enter the windings. It is good enough to get a wire spliced onto it but I would like to stabilize the point where it enters the transformer. This transformer was inside of a metal housing and poured with a generous layer of tar to stabilize everything - including the laminations as those can be noisy. While tar would probably work, I'd rather use something else and only at the point where these two wires enter the core to hopefully prevent further breakage after the splice is made. I'm thinking of making a small form at the end of the core around the wires and pour a potting compound of sorts in the form. My first thoughts would be something akin to silicone sealant but, as I understand it, that stuff is not kind to wiring. Roofing tar might work if it sets up firmly enough but, again, would like to steer clear of more tar. Is there something out there that would work well for this? Feel free to respond directly to me. Thanks, Barry - N4BUQ -- ----------------------------------------------------------------------- Glenn Little ARRL Technical Specialist QCWA LM 28417 Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178 QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"
- All Messages By This Member #182006 Barry, Ordinary household silicone sealant releases Acetic Acid as it cures so you're right, it's not kind to most metals. But they also make an electronics grade silicone sealant that won't harm metal. I don't know if it's suitable for your transformer but I thought that you might like to know. toggle quoted message Show quoted text On Tue, Apr 27, 2021 at 11:14 PM n4buq <n4buq@...> wrote: I just don't know where there's an appropriate group for this so thought I'd ask here. I have a transformer (out of a fairly old SOLA CVT) whose 115V input leads have become fragile right at the point where they enter the windings. It is good enough to get a wire spliced onto it but I would like to stabilize the point where it enters the transformer. This transformer was inside of a metal housing and poured with a generous layer of tar to stabilize everything - including the laminations as those can be noisy. While tar would probably work, I'd rather use something else and only at the point where these two wires enter the core to hopefully prevent further breakage after the splice is made. I'm thinking of making a small form at the end of the core around the wires and pour a potting compound of sorts in the form. My first thoughts would be something akin to silicone sealant but, as I understand it, that stuff is not kind to wiring. Roofing tar might work if it sets up firmly enough but, again, would like to steer clear of more tar. Is there something out there that would work well for this? Feel free to respond directly to me. Thanks, Barry - N4BUQ
Jeff Dutky Member Profile All Messages By This Member #182007 Here's someone using "Shoe Goo" urethane to hand make strain relief on cables. It may work in this application as well. -- Jeff Dutky
Jean-Paul All Messages By This Member #182013 Barry, the silicone is not strong enough, I have fixed this problem with a small c clamp strain relief screwed on to the new wires. Instead of tar or silicone I have used hot melt glue, but first clean all surfaces with isopropyl alcohol. Jon
SCMenasian All Messages By This Member #182017 You can consider a 2 part potting compound. A while back, I bought some Dow Corning Sylgard 160, which comes in dual tube 400 ml units. It is intended to be dispensed with a special "caulking gun" type tool with a mixing nozzle. It was originally intended for a solar panel project which never happened because I found some manufactured panels at a good price. I, now, use the Sylgard for general potting, etc. Instead of dispensing the entire 400 ml at once, I just dispense whatever small amount I want into a small container and mix it manually. It cures, at room temperature, in about a day - faster in the oven. Beware; Its very strong and sticky. I made an initial mistake of using a glass 50 ml beaker and allowed it to set up before cleaning the beaker. I don't know if I will ever get the cured material out without breaking the beaker. I'm very careful to clean the tube ends and cap completely before putting the cap back on after I'm through.

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