[volt-nuts] volt-nuts Digest, Vol 7, Issue 9

[J. Forster]

I use almost nothing else but the clear. The HySol (Dexter now, I think)
is really good stuff. In the refrigerator it keeps for many years too.

-John

==============


> One of the things I like about slow setting epoxy is that heat not only
> speeds up the cure but improves the bond too. I'm so conditioned to expect
> every gain to come at a price that this really surprised me when I first
> heard about it.
>
> Alan
>
>
> ----- Original Message -----
> From: "J. Forster" <jfor at quik.com>
> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
> Sent: Wednesday, March 17, 2010 8:19 PM
> Subject: Re: [volt-nuts] volt-nuts Digest, Vol 7, Issue 9
>
>
>> The epoxy I use for repais on circuit boards is completely clear
>> two-part
>> without any fillers from HySol. Do not use the 5 minute setting stuff
>> either. You want something that takes several hours to set up. That's
>> much
>> better stuff.
>>
>> -John
>>
>> ==============
>>
>>
>>
>> [snip] I wouldn't be sure
>>> that using the automotive epoxy would be a good idea...
>>>
>>> Dick Moore
>>>
>>>
>>> On Mar 17, 2010, at 5:00 AM, volt-nuts-request at febo.com wrote:
>>>
>>>>
>>>> Message: 6
>>>> Date: Wed, 17 Mar 2010 11:20:37 -0000
>>>> From: "Alan Scrimgeour" <scrimgap at blueyonder.co.uk>
>>>> Subject: Re: [volt-nuts] Keithley 2001 Multimeter Fault - Update
>>>> To: <jfor at quik.com>, "Discussion of precise voltage measurement"
>>>> <volt-nuts at febo.com>
>>>> Message-ID: <AE27F40615CE4CA08494C3AD153F4414 at AlanPC>
>>>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>>>> reply-type=original
>>>>
>>>> Perhaps only the copper was 'etched', but I can imagine even epoxy
>>>> being
>>>> attacked by hot electrolysis taking place right next to it.
>>>> Electrolysis
>>>> could produce some very active compounds, depending on the electrolyte
>>>> (and,
>>>> I'm not sure, but in such close proximity to the electrodes there may
>>>> also
>>>> be some extremely reactive short lived species, or is that just
>>>> Sci-Fi?).
>>>> But by some mechanism the upper layer of glass fiber in the board was
>>>> visible before I started digging it away.
>>>>
>>>> The excavation is progressing with care. In the centre the damage has
>>>> gone
>>>> right through the board to virtually the other side. Presumably air
>>>> cooling
>>>> stopped or slowed the progress of the damage actually through the very
>>>> last
>>>> layers of the board.  It appears that once the hot electrolysis had
>>>> begun to
>>>> damage the pcb it carbonised and in that conductive state, drew
>>>> current
>>>> and
>>>> generated yet more heat leading to a chain reaction in the form of a
>>>> growing
>>>> carbonised region.
>>>>
>>>> I've just had to cut a wide buried copper track in order to be able to
>>>> remove the carbonised pcb beneath it, which is disconcerting, but it
>>>> will
>>>> just need soldering, or replacing with a piece of wire. I'm more
>>>> worried
>>>> about what to use as a 'filling' in this cavity. I said I'd use epoxy
>>>> resin,
>>>> but the usual stuff is damaged by soldering temperatures. I have some
>>>> 'Auto
>>>> Weld' which says it's resistant to a constant 300C and should do. Once
>>>> I
>>>> fill that hole back I'll never get it out again, so I'd better fix it
>>>> properly!
>>>> I'd like to add that I'm feeling pretty angry about those electrolytic
>>>> capacitors. They are sheer vandalism! Time for some companies heads to
>>>> bow
>>>> down and appologise! Those unstable low dropout regulators are another
>>>> annoying self destruct mechanism too!!!
>>>>
>>>> Alan
>>>
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>>
>>
>>
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