Repairing a Guideline 9230A-15 Current Shunt - Page 1
Forum section: electronics / general

author: Tony_G
author_rank: Super Contributor
timestamp: October 15, 2025, 11:23:59 pm
content: Hey All,I dumpster dove this current shunt that was thrown out because it has a break in a copper wire:Given that it is connected to a massive block of copper, how best should I approach trying to repair this? I'm not sure my iron is ever going to get the wire hot enough to solder it and I have no idea what soldering it will introduce in terms of errors.Any thoughts or comments?Thanks,TonyG

author: zlymex
author_rank: Frequent Contributor
timestamp: October 16, 2025, 07:43:10 am
content: I would use a thin copper wire to solder the connection, as it is just a potential lead. Do not attempt to directly re-solder it, as that would introduce significant stress.

author: Overspeed
author_rank: Frequent Contributor
timestamp: October 16, 2025, 07:59:16 am
content: HelloYou can try a sport welder as in use for thermocouple ?That can possible to clear a bit the short side broken wireRegardsOS

author: edpalmer42
author_rank: Super Contributor
timestamp: October 16, 2025, 07:56:40 pm
content: I'm not sure what I'm seeing. It looks like there's a random silver wire attached to the end of the broken wire. Is that original or has this shunt been victimized in the past? If it has been messed with, the calibration is suspect.What does the bottom look like? Is the broken wire a continuous piece from the shunt to the potential terminal? Are there existing solder connections in that connection? Can you see how the broken wire is attached to the copper block (under the black paint)?If there are already solder connections in the potential lead it's unlikely that another one will make a significant difference. Even better, if you can redesign the connection to remove an existing solder connection, you can then add a new solder connection with even less effect on the calibration.In any case, soldering to the broken wire stub will be a problem. An iron won't do it. You'll have to use either a micro propane or butane torch to get enough heat to get in and out quickly. You might need to disassemble the shunt completely and preheat the copper parts in an oven.

author: Tony_G
author_rank: Super Contributor
timestamp: October 16, 2025, 08:06:27 pm
content: Hey Ed,I believe this is from the factory (I can't find anything on what the smaller wired device is, but I think it might be some form of temperature-dependent resistor so that it corrects for the main wire heating up and helps maintain the 0.5 ohm rating).QuoteThis was my concern with trying to repair the wire completely - I was thinking that maybe I could get just enough in to solder a small wire to provide connectivity.TonyG

author: edpalmer42
author_rank: Super Contributor
timestamp: October 16, 2025, 11:06:32 pm
content: Quote from: Tony_G on October 16, 2025, 08:06:27 pmIt seems unlikely to me that a shunt with 100 PPM accuracy would use a temperature-dependent resistor. I can't find a good picture online, but the ones I can find don't show anything like that. I'm suspicious.....QuoteIt's worth a shot. Remember that the copper will be heavily oxidized. You'll need to really clean the stub - maybe steel wool or a wire brush - and then add extra liquid flux before you start heating.

author: Tony_G
author_rank: Super Contributor
timestamp: October 16, 2025, 11:37:25 pm
content: Hmm..QuoteFrom the datasheet - I think you're right:I'll have to open it up and take a look.TonyG

author: Tony_G
author_rank: Super Contributor
timestamp: October 16, 2025, 11:42:12 pm
content: And here is what is in that shrink wrap...TonyG

author: zlymex
author_rank: Frequent Contributor
timestamp: October 18, 2025 12:57:59 am
content: Quote from: Tony_G on October 16, 2025, 08:06:27 pmIt is a hermetic metal foil resistor for value compensation.As far as l know, resistor compensation can be categorized into four main types:1. Aging CompensationThis method is quite complex to implement, and I see no practical cases of its application.2. β Temperature Drift CompensationThis approach is relatively complicated requiring calculations and the use of NTC thermistors, with limited real-world examples.3. α Temperature Drift CompensationThe compensation calculation is relatively straight forward and can be further divided into several specific methods, such as copper resistance compensation, Pt100/Pt1000 compensation and lead wire compensation.4. Resistance Value CompensationThis is the most common method: for low-value standard resistors and shunts parallel compensation is typically used where as for high-value resistors, series compensation is generally employed.

author: edpalmer42
author_rank: Super Contributor
timestamp: October 18, 2025 02:12:49 am
content: Quote from: zlymex onYesterdayat 12:57:59 amIt certainly looks like that. But remember that it's in parallel with a nominal 0R5 shunt. And across the potential terminals that aren't supposed to see any current.  The black cylinder on the main shunt wire appears to be original since there are two of them. Insulators? Maybe just used for mechanical support of the resistor rather than thermal compensation?This looks very weird to me. Is this the way that Guildline tweaks their shunts? And their pretty pictures don't show the tweaks? Weston-style shunts typically have the edge of the shunt ground down to adjust the resistance. This seems much too crude for a Guildline Precision Shunt. Their stuff is practically a work of art - particularly the older stuff.But, it is what it is. Leave it for now and carry on with the repair. Looking at the datasheet and manual, I'm not seeing any info on what kind of meter should be used on those potential terminals. Maybe Guildline includes that info in an app note somewhere. I often see things like "a 5 amp meter connected by leads with a resistance of 0R1 ohms" or whatever is appropriate. If you don't follow those instructions, you mess up the calibration.