Electronics > Repair

Desoldering advice

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KrudyZ:
I don't get why you are trying to save the relay.
You can certainly test its function while soldered in place.
If it tests good, then it's not your problem.
If it's bad then just get it out by all means, the easiest is to deconstruct (destroy) it from the top by sawing grinding snipping whatever works.
Then you can work on each solder joint separately, which should be trivial.

antenna:
Thanks for the preheating and bigger soldering iron advice, the relay came right out.

It tested fine, all components under it tested good too.  I used some 63-37 and wicked it off to remove the low MP alloy, then put the relay back in with some Sn Cu Ag stuff that melts at 237°C instead of using the 60-40 188°C stuff I usually use.  I found no continuity at the motor, so their "low voltage" error code must have meant low current.  It seems that when it detects no current, the relay drops out.  Opening the motor and checking the brushes next. 

I appreciate all the help, thank you!

Update:  The commutator was dirty and the brushes were stuck.  The scooter is fixed!

fmashockie:
Glad to hear it! And that you got the scooter working!

It may not have been the original cause you were thinking, but you got to it eventually.  Plus you learned a new skill along the way!

tooki:

--- Quote from: antenna on April 28, 2024, 06:54:47 pm ---It tested fine, all components under it tested good too.  I used some 63-37 and wicked it off to remove the low MP alloy, then put the relay back in with some Sn Cu Ag stuff that melts at 237°C instead of using the 60-40 188°C stuff I usually use.

--- End quote ---
I assume your SnAgCu is actually 227C.

Anyhow, in the future, I’d avoid mixing up all these alloys — or at least “rinse” with your final solder multiple times. In particular, what you really want to avoid is soldering with tin-bismuth after using tin-lead: lead lowers the melting point substantially, and can result in an alloy that melts below 100C!

antenna:

--- Quote from: tooki on April 29, 2024, 03:07:51 pm ---
--- Quote from: antenna on April 28, 2024, 06:54:47 pm ---It tested fine, all components under it tested good too.  I used some 63-37 and wicked it off to remove the low MP alloy, then put the relay back in with some Sn Cu Ag stuff that melts at 237°C instead of using the 60-40 188°C stuff I usually use.

--- End quote ---
I assume your SnAgCu is actually 227C.

Anyhow, in the future, I’d avoid mixing up all these alloys — or at least “rinse” with your final solder multiple times. In particular, what you really want to avoid is soldering with tin-bismuth after using tin-lead: lead lowers the melting point substantially, and can result in an alloy that melts below 100C!

--- End quote ---
Looking at it closer, it is a Sn Cu Bi Ag alloy that I used, and looking it up, the MP is supposed to be between 215°C and 233°C. The surface was cleaned with wick fairly well though and when I applied this stuff, I had to crank it up to get it to flow.  I will remember not to mix alloys in the future though.  Thanks!

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