Eric The Viking
Established Member
- Joined
- 19 Jan 2010
- Messages
- 6,599
- Reaction score
- 74
... resoldering the line output transistor and transformer in daughter #1's eMac.
It took around four hours to work out how to get it apart without breaking anything (that bit is most decidedly NOT supposed to be user serviceable). Still it was gratifying to find broken/dry solder joints exactly where they might have been expected given the symptoms (display collapsing, but sometimes coming back when she thumped it!).
Last week I replaced eight electrolytics on the motherboard, which also took ages.
Why bore you lot with all this? Three horrible words: lead-free solder!
Basically it's rubbish. The melting point is about 30deg C hotter than leaded, it's brittle and it doesn't wet the copper surfaces at all well. I've more than a few soldering irons, including one bought specifically because it was supposed to be 'suitable' for lead free work. None of the electronics-sized ones work satisfactorily.
On the motherboard, I couldn't desolder the plated-through holes satisfactorily (after hours of trying). None of my favourite techniques, even cooking the end of the iron in the DC's kitchen blowlamp, didn't work. You could have molten solder on one side of the board and solid metal on t'other. My three solder suckers were all almost useless. I was reduced to drilling out the last few holes as I simply couldn't spend any more time on it.
The scary thing though was the failure modes of the tube drive components: two joints, one on the LOPT and one on the drive transistor, had annular fractures half-way up the solder cone. The machine isn't subject to vibration (unless you count LOPT 'singing'), so this was a surprise. There are a few other suspect joints I've cleaned off and re-soldered - happily the power/tube drive board is single-sided, and easier to desolder.
If these problems are common, the reliability of electronic devices must plummet, especially in applications like vehicles and aerospace, which are subject to vibration and large temperature variations.
Thank you, nameless and unaccountable mandarins of the EU, for Directive 2002/95/EC. I hope several 'fly-by-wire-not' jets crash on your houses :twisted:
... After the debacle of the smoothing caps on the motherboard, I took a deep breath and went to Maplins. They have some silver solder (horrifically expensive, as you might expect), which seems to be compatible with the lead free whatever, but has a lower melting point. It seems to have worked with the LOPT, etc., but the finished joints look really horrible - in a leaded solder environment I'd be re-making them as they look dry (although they can't be). In two hours time I'll know if it's worked.
This has been a tedious and sobering experience, more so as I know she's not grateful (she was hoping I wouldn't mend it and she'd get a Macbook instead!).
Is it just me or is the world going bonkers?
It took around four hours to work out how to get it apart without breaking anything (that bit is most decidedly NOT supposed to be user serviceable). Still it was gratifying to find broken/dry solder joints exactly where they might have been expected given the symptoms (display collapsing, but sometimes coming back when she thumped it!).
Last week I replaced eight electrolytics on the motherboard, which also took ages.
Why bore you lot with all this? Three horrible words: lead-free solder!
Basically it's rubbish. The melting point is about 30deg C hotter than leaded, it's brittle and it doesn't wet the copper surfaces at all well. I've more than a few soldering irons, including one bought specifically because it was supposed to be 'suitable' for lead free work. None of the electronics-sized ones work satisfactorily.
On the motherboard, I couldn't desolder the plated-through holes satisfactorily (after hours of trying). None of my favourite techniques, even cooking the end of the iron in the DC's kitchen blowlamp, didn't work. You could have molten solder on one side of the board and solid metal on t'other. My three solder suckers were all almost useless. I was reduced to drilling out the last few holes as I simply couldn't spend any more time on it.
The scary thing though was the failure modes of the tube drive components: two joints, one on the LOPT and one on the drive transistor, had annular fractures half-way up the solder cone. The machine isn't subject to vibration (unless you count LOPT 'singing'), so this was a surprise. There are a few other suspect joints I've cleaned off and re-soldered - happily the power/tube drive board is single-sided, and easier to desolder.
If these problems are common, the reliability of electronic devices must plummet, especially in applications like vehicles and aerospace, which are subject to vibration and large temperature variations.
Thank you, nameless and unaccountable mandarins of the EU, for Directive 2002/95/EC. I hope several 'fly-by-wire-not' jets crash on your houses :twisted:
... After the debacle of the smoothing caps on the motherboard, I took a deep breath and went to Maplins. They have some silver solder (horrifically expensive, as you might expect), which seems to be compatible with the lead free whatever, but has a lower melting point. It seems to have worked with the LOPT, etc., but the finished joints look really horrible - in a leaded solder environment I'd be re-making them as they look dry (although they can't be). In two hours time I'll know if it's worked.
This has been a tedious and sobering experience, more so as I know she's not grateful (she was hoping I wouldn't mend it and she'd get a Macbook instead!).
Is it just me or is the world going bonkers?
this lead free is awful
