Desoldering pump to avoid

[Phil Allison]

Actually I usually try to cut pins on chips when I'm trying to isolate a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?

** Won't help if there is a short on a 5V DC supply rail with many ICs and ceramic caps across it. Best way to find the culprit is to use the "tune for maximum smoke" technique.

Apply a bench supply to the rail that has enough current to *smoke out" out the cap or IC that is shorted.

Finds bad tantalums and ceramics in a couple of seconds, bad ICs may be found with a finger test - AKA the "ouch" test.

Anyone who has serviced amplifiers using Hitachi TO3 mosfets in parallel groups knows a finger test works to find any dead ones. Do I need to explain?

FYI:

Hitachi TO3 mosfets have internal fuses that can isolate a bad device during a short or other overload - the amp keeps working albeit at somewhat reduced power capacity. Gotta love that.



...... Phil

 

[Clocky]

On 8/04/2017 12:11 PM, keithr0 wrote:

On 4/8/2017 8:17 AM, Clocky wrote:
On 8/04/2017 4:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

Does it look like this?

https://tronixstuff.files.wordpress.com/2012/09/suckersmall.jpg

I think I still have the one I bought from Tandy 30-odd years ago
somewhere, not that it was any good.


None of them are, the best method is solder wick, used properly it will
leave everything just as new. When I worked for NASA, it was the only
approved method of de-soldering.

Been there, done that but no, desoldering gun is the go-to for mine -
works fast and well. YMMV.

 

[keithr0]

On 4/5/2017 9:59 PM, Computer Nerd Kev wrote:

Trevor Wilson <trevor@spamblockrageaudio.com.au> wrote:
On 5/04/2017 8:41 AM, Trevor Wilson wrote:
On 5/04/2017 8:19 AM, Computer Nerd Kev wrote:
Phil Allison <pallison49@gmail.com> wrote:
Trevor Wilson wrote:


However, when you REALLY want to desolder stuff, this is what you need:

https://www.hakko.com/english/products/hakko_fr300.html

WES can supply. It is a beautifully built desoldering iron, which has
saved me a great deal of time and money. Damage to PCBs is minimised
with this device.


** I need to remove some 16 pin DILs from a triple layer PCB ( ground
plane in the middle ) while not damaging them. So far, only pin cutting
and tedious removal of the each legs is working for me.

Do you have a trick for cutting the pins? I can never get any of my side
cutters in close enough.


**Look for 'flush cutters'. That said, a credible argument can be
mounted to suggest that cutting pins after soldering is not a good idea,
as the stress of cutting may cause a fracture in the joint. Unlikely,
but possible. Best to cut first, then solder.


**Oops. Ignore that. I mis-read your post. A good desoldering iron will
do all you require.

Actually I usually try to cut pins on chips when I'm trying to isolate a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?

 

[keithr0]

On 4/8/2017 8:17 AM, Clocky wrote:

On 8/04/2017 4:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

Does it look like this?

https://tronixstuff.files.wordpress.com/2012/09/suckersmall.jpg

I think I still have the one I bought from Tandy 30-odd years ago
somewhere, not that it was any good.

None of them are, the best method is solder wick, used properly it will
leave everything just as new. When I worked for NASA, it was the only
approved method of de-soldering.

 

[Trevor Wilson]

On 8/04/2017 8:12 AM, Clocky wrote:

On 8/04/2017 4:18 AM, Trevor Wilson wrote:
On 7/04/2017 8:21 PM, keithr0 wrote:
On 4/7/2017 12:57 PM, ~misfit~ wrote:
Once upon a time on usenet keithr0 wrote:
On 4/6/2017 6:54 AM, Trevor Wilson wrote:
On 5/04/2017 9:04 PM, keithr0 wrote:
On 4/5/2017 6:36 PM, Trevor Wilson wrote:
On 5/04/2017 6:31 PM, Sylvia Else wrote:
On 5/04/2017 1:46 PM, keithr0 wrote:
On 4/3/2017 10:05 PM, Sylvia Else wrote:
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the
handle sharply upwards towards any vulnerable body part, with
the eyes being the most obvious targets.

Sylvia.

I've seen similar devices in use for the last 50 years and have
never known anybody hurt themselves with one.

Probably because the devices they use don't self-disassemble the
way this one does.


**Stop supporting Jaycar. I did. I've been much happier. Use a
proper supplier, like Element14, RS Components, X-ON, or even WES.

From where I live its 20 minutes to Jaycar, 40 minutes to Altronics,
over an hour to RS, the others aren't in QLD so a day or maybe two.

So its usually Jaycar if they stock what I need.


**RS offer free delivery and Element14 have a temporary free delivery
option right now. For my part, I'd rather pay the $10.00 ~ $15.00
delivery charge, than waste a 40 minute round trip to buy rubbish.
Life it too short to support some rich guy's Ferrari fetish, by
buying junk that fails quickly.

I've never had any of the stuff that I've bought from Jaycar fail. I'm
only in it for myself these days and if I want it, I want it now (or
at least within the hour). Ordering from RS may get it today or more
probably tomorrow, from the others it will have to come from Sydney,
best estimate 2 days maybe more. Lifes too short to wait that long.

You are very lucky indeed then. More than half of the last half a dozen
things I bought from Jaycar failed - some taking connected equipment
with
them. For me the 'conveinence' of Jaycar will never again be put
ahead of
the general low quality of their stock. This even though there's a
Jaycar
store 5 minutes drive from my home and any other option is 24 hours
mimimum.

The lab power supply that I got from there is still working OK and the
resistors, capacitors, switches, connectors etc from there have worked
just as well as from anywhere.

I do believe that there is an element of snobbery in those who put them
down, their stuff is probably not the best, but it is adequate. Their
main problem is that they do not carry the range of stuff that RS etc
do. I buy a lot of stuff (where it isn't urgent) from China and nothing
from there has let me down either.

**"Snobbery"? No. Here is ONE of my many experiences with their rubbish:

Back in the mid-1990s, I ordered and received 500, 15VAC, 300ma
plugpacks for a job I was commissioned to do for a client. Their pricing
was pretty good (around $5.00, I think). After a short time, failures
began. I scrambled to find an alternate supply. Telectran in Terrey
Hills, Sydney quoted me on an Australian made replacement. $14.00 each.
My client agreed, so we pulled all the old power supplies off the market
and replaced them with the new ones. The Jaycar supplies registered a 7%
failure rate within 3 months, before they were removed from the market.
In the four years after the replacements were supplied, I registered a
total of 3 failures out of 500 power supplies.

It just goes to show that some people are happy to pay for a bit of
quality.

That said, I recognise that a professional's requirements may be
different to a home user. For a professional, a component failure can
have far-reaching effects. For an amateur, it may just be a nuisance.



How about another example?

**How about a few?

* I ordered some floating pool lights. All three leaked. You'd reckon
that, in a pool light, it's ability to remain water-tight would be the
most important criteria. Nope. Not for a Jaycar pool light. They weren't
even submerged. Just designed to float on the surface. Zero water
pressure and the damned things still leaked.

* A home alarm system, which had two faulty sensors. Incredible.


--
Trevor Wilson
www.rageaudio.com.au

 

[Trevor Wilson]

On 8/04/2017 6:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

**Then you need to try the Edsyn one I suggested. I've been using them
for decades. They're excellent and will likely provide many years of
service for an amateur. Even in regular, daily use, they last a couple
of years (along with regular tip replacement and re-greasing, of course).


--
Trevor Wilson
www.rageaudio.com.au

 

[~misfit~]

Once upon a time on usenet keithr0 wrote:

On 4/7/2017 12:57 PM, ~misfit~ wrote:
Once upon a time on usenet keithr0 wrote:
On 4/6/2017 6:54 AM, Trevor Wilson wrote:
On 5/04/2017 9:04 PM, keithr0 wrote:
On 4/5/2017 6:36 PM, Trevor Wilson wrote:
On 5/04/2017 6:31 PM, Sylvia Else wrote:
On 5/04/2017 1:46 PM, keithr0 wrote:
On 4/3/2017 10:05 PM, Sylvia Else wrote:
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the
handle sharply upwards towards any vulnerable body part, with
the eyes being the most obvious targets.

Sylvia.

I've seen similar devices in use for the last 50 years and have
never known anybody hurt themselves with one.

Probably because the devices they use don't self-disassemble the
way this one does.


**Stop supporting Jaycar. I did. I've been much happier. Use a
proper supplier, like Element14, RS Components, X-ON, or even
WES.

From where I live its 20 minutes to Jaycar, 40 minutes to
Altronics, over an hour to RS, the others aren't in QLD so a day
or maybe two. So its usually Jaycar if they stock what I need.


**RS offer free delivery and Element14 have a temporary free
delivery option right now. For my part, I'd rather pay the $10.00
~ $15.00 delivery charge, than waste a 40 minute round trip to buy
rubbish. Life it too short to support some rich guy's Ferrari
fetish, by buying junk that fails quickly.

I've never had any of the stuff that I've bought from Jaycar fail.
I'm only in it for myself these days and if I want it, I want it
now (or at least within the hour). Ordering from RS may get it
today or more probably tomorrow, from the others it will have to
come from Sydney, best estimate 2 days maybe more. Lifes too short
to wait that long.

You are very lucky indeed then. More than half of the last half a
dozen things I bought from Jaycar failed - some taking connected
equipment with them. For me the 'conveinence' of Jaycar will never
again be put ahead of the general low quality of their stock. This
even though there's a Jaycar store 5 minutes drive from my home and
any other option is 24 hours mimimum.
The lab power supply that I got from there is still working OK and the
resistors, capacitors, switches, connectors etc from there have worked
just as well as from anywhere.

I do believe that there is an element of snobbery in those who put
them down, their stuff is probably not the best, but it is adequate.
Their main problem is that they do not carry the range of stuff that
RS etc do. I buy a lot of stuff (where it isn't urgent) from China
and nothing from there has let me down either.

No snobbery here (but thanks for the accusation). I used to buy quite a bit
of stuff from them until I got stung one too many times.

Two of the last few things I bought from them; One was a ~$35 DMM (as a
stop-gap because mine failed mid-job) and when I got it home I noticed the
minus sign on the display didn't work. Took it back the next day and was as
much as accused of damaging it myself. How they thought I did that I don't
know.

The other thing was a "Watts Clever" RF remote controlled set of 3 mains
switches. One failed after a couple of months but I let it go as I only
really needed two anyway. Just after the 12 month warranty expired another
failed by cycling it's mains switching relay at 50Hz for the 3 minutes it
took for me to get behind the stereo to unplug it. It blew fuses in the
amplifier and killed the SMPS in a CD player.

Now I'd rather just go without than risk buying anything from them.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

Actually I usually try to cut pins on chips when I'm trying to
isolate a fault and don't want to cut the PCB (or veroboard)
tracks. A bit of component lead is soldered over the break after
I'm satisfied. I have managed it sometimes, but with great
difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?


** Won't help if there is a short on a 5V DC supply rail with many
ICs and ceramic caps across it. Best way to find the culprit is to
use the "tune for maximum smoke" technique.

Apply a bench supply to the rail that has enough current to *smoke
out" out the cap or IC that is shorted.

Finds bad tantalums and ceramics in a couple of seconds, bad ICs may
be found with a finger test - AKA the "ouch" test.

Anyone who has serviced amplifiers using Hitachi TO3 mosfets in
parallel groups knows a finger test works to find any dead ones. Do I
need to explain?

FYI:

Hitachi TO3 mosfets have internal fuses that can isolate a bad device
during a short or other overload - the amp keeps working albeit at
somewhat reduced power capacity. Gotta love that.

Yep. I'm in the process of reconfiguring a pair of 100w mono amps that are
running two each J50 / K135 each to run on an extra +/- 15v (and doubling
the 2 x 10,000 uF of smoothing caps to 2 x 20,000 uF) and paralleling a
third pair of MOSFETs per amp (on small perfboard daughterboards and fly
leads), then building them both with their power supplies into a big
(re-purposed Perreaux PA amp) case and adding a couple speaker protection
modules.

They already sound really good with two pairs of devices each and +/- 60v
rails. They should sound awesome with three pairs and +/- 75v rails. <g>
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Clocky]

On 8/04/2017 12:00 PM, Trevor Wilson wrote:

On 8/04/2017 8:12 AM, Clocky wrote:
On 8/04/2017 4:18 AM, Trevor Wilson wrote:
On 7/04/2017 8:21 PM, keithr0 wrote:
On 4/7/2017 12:57 PM, ~misfit~ wrote:
Once upon a time on usenet keithr0 wrote:
On 4/6/2017 6:54 AM, Trevor Wilson wrote:
On 5/04/2017 9:04 PM, keithr0 wrote:
On 4/5/2017 6:36 PM, Trevor Wilson wrote:
On 5/04/2017 6:31 PM, Sylvia Else wrote:
On 5/04/2017 1:46 PM, keithr0 wrote:
On 4/3/2017 10:05 PM, Sylvia Else wrote:
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the
handle sharply upwards towards any vulnerable body part, with
the eyes being the most obvious targets.

Sylvia.

I've seen similar devices in use for the last 50 years and have
never known anybody hurt themselves with one.

Probably because the devices they use don't self-disassemble the
way this one does.


**Stop supporting Jaycar. I did. I've been much happier. Use a
proper supplier, like Element14, RS Components, X-ON, or even WES.

From where I live its 20 minutes to Jaycar, 40 minutes to
Altronics,
over an hour to RS, the others aren't in QLD so a day or maybe two.

So its usually Jaycar if they stock what I need.


**RS offer free delivery and Element14 have a temporary free
delivery
option right now. For my part, I'd rather pay the $10.00 ~ $15.00
delivery charge, than waste a 40 minute round trip to buy rubbish.
Life it too short to support some rich guy's Ferrari fetish, by
buying junk that fails quickly.

I've never had any of the stuff that I've bought from Jaycar fail.
I'm
only in it for myself these days and if I want it, I want it now (or
at least within the hour). Ordering from RS may get it today or more
probably tomorrow, from the others it will have to come from Sydney,
best estimate 2 days maybe more. Lifes too short to wait that long.

You are very lucky indeed then. More than half of the last half a
dozen
things I bought from Jaycar failed - some taking connected equipment
with
them. For me the 'conveinence' of Jaycar will never again be put
ahead of
the general low quality of their stock. This even though there's a
Jaycar
store 5 minutes drive from my home and any other option is 24 hours
mimimum.

The lab power supply that I got from there is still working OK and the
resistors, capacitors, switches, connectors etc from there have worked
just as well as from anywhere.

I do believe that there is an element of snobbery in those who put them
down, their stuff is probably not the best, but it is adequate. Their
main problem is that they do not carry the range of stuff that RS etc
do. I buy a lot of stuff (where it isn't urgent) from China and nothing
from there has let me down either.

**"Snobbery"? No. Here is ONE of my many experiences with their rubbish:

Back in the mid-1990s, I ordered and received 500, 15VAC, 300ma
plugpacks for a job I was commissioned to do for a client. Their pricing
was pretty good (around $5.00, I think). After a short time, failures
began. I scrambled to find an alternate supply. Telectran in Terrey
Hills, Sydney quoted me on an Australian made replacement. $14.00 each.
My client agreed, so we pulled all the old power supplies off the market
and replaced them with the new ones. The Jaycar supplies registered a 7%
failure rate within 3 months, before they were removed from the market.
In the four years after the replacements were supplied, I registered a
total of 3 failures out of 500 power supplies.

It just goes to show that some people are happy to pay for a bit of
quality.

That said, I recognise that a professional's requirements may be
different to a home user. For a professional, a component failure can
have far-reaching effects. For an amateur, it may just be a nuisance.



How about another example?

**How about a few?

* I ordered some floating pool lights. All three leaked. You'd reckon
that, in a pool light, it's ability to remain water-tight would be the
most important criteria. Nope. Not for a Jaycar pool light. They weren't
even submerged. Just designed to float on the surface. Zero water
pressure and the damned things still leaked.

* A home alarm system, which had two faulty sensors. Incredible.

It's getting to be quite a list so I'll add my own experiences . I don't
buy much from them.

Capacitors... they're junk. Also, I was given an adjustable magnifying
lamp the kind that clamps to the edge of the desk. The arm is great, the
light LED works well... but the magnifying glass is large but the board
needs to be so close to the lens to see clearly that it blocks access
with a soldering iron... sigh.

 

[Benderthe.evilrobot]

"Phil Allison" <pallison49@gmail.com> wrote in message
news:a79ee72b-ee65-49f2-bd28-5646558a8b07@googlegroups.com...

Actually I usually try to cut pins on chips when I'm trying to isolate
a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?


** Won't help if there is a short on a 5V DC supply rail with many ICs and
ceramic caps across it. Best way to find the culprit is to use the "tune
for maximum smoke" technique.

Apply a bench supply to the rail that has enough current to *smoke out"
out the cap or IC that is shorted.

With a shorted ceramic cap - the smoke could come from a narrow section of
PCB supply track.

The method isn't without its merits though.


---
This email has been checked for viruses by AVG.
http://www.avg.com

 

[Benderthe.evilrobot]

"Clocky" <notgonn@happen.com> wrote in message
news:58e80ff3$0$1535$c3e8da3$5496439d@news.astraweb.com...

On 8/04/2017 4:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

Does it look like this?

https://tronixstuff.files.wordpress.com/2012/09/suckersmall.jpg

I've had a few like that - but they all left me for a thieving
git..............

This one is double the length and the plunger rod isn't attached to the
plunger itself, a spring returns it to fully extended position when you let
it go.

The plunger assembly has a hollow core so the the plunger operating rod
still pokes a pin through to clear the nozzle.


---
This email has been checked for viruses by AVG.
http://www.avg.com

 

[Benderthe.evilrobot]

"keithr0" <user@account.invalid> wrote in message
news:ekr66uFab3pU1@mid.individual.net...

On 4/8/2017 8:17 AM, Clocky wrote:
On 8/04/2017 4:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

Does it look like this?

https://tronixstuff.files.wordpress.com/2012/09/suckersmall.jpg

I think I still have the one I bought from Tandy 30-odd years ago
somewhere, not that it was any good.


None of them are, the best method is solder wick, used properly it will
leave everything just as new. When I worked for NASA, it was the only
approved method of de-soldering.

Multilayer boards do heatsinking too well - solder wick can get stuck on and
make it too easy to pull tracks off.


---
This email has been checked for viruses by AVG.
http://www.avg.com

 

[Computer Nerd Kev]

Benderthe.evilrobot <Benderthe.evilrobot@virginmedia.com> wrote:

"Computer Nerd Kev" <not@telling.you.invalid> wrote in message
newsc2m73$1qud$1@gioia.aioe.org...
Trevor Wilson <trevor@spamblockrageaudio.com.au> wrote:
On 5/04/2017 8:41 AM, Trevor Wilson wrote:

**Look for 'flush cutters'. That said, a credible argument can be
mounted to suggest that cutting pins after soldering is not a good idea,
as the stress of cutting may cause a fracture in the joint. Unlikely,
but possible. Best to cut first, then solder.


**Oops. Ignore that. I mis-read your post. A good desoldering iron will
do all you require.

Actually I usually try to cut pins on chips when I'm trying to isolate a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

Cut tracks with a scalpel held at a sharp angle so the cut edges overlap.
flat it down after with the iron tip - it doesn't take much solder to secure
the join.

I've tried a scalpel and often find I accidently jump over a few
tracks and leave a big slice over the board. Then I have to check
each of the other tracks to make sure I didn't accidently cut
through them, but usually I haven't because I usually have to
make multiple runs over a track with the scalpel to get all the
way through.

It can also be difficult to run solder over small tracks without
risk of lifting them. And on a proper modern PCB you'd have to
scrape off the solder mask.

If cutting the pins is an option, I take it.

--
__ __
#_ < |\| |< _#

 

[Computer Nerd Kev]

keithr0 <user@account.invalid> wrote:

On 4/5/2017 9:59 PM, Computer Nerd Kev wrote:
Trevor Wilson <trevor@spamblockrageaudio.com.au> wrote:
On 5/04/2017 8:41 AM, Trevor Wilson wrote:

**Look for 'flush cutters'. That said, a credible argument can be
mounted to suggest that cutting pins after soldering is not a good idea,
as the stress of cutting may cause a fracture in the joint. Unlikely,
but possible. Best to cut first, then solder.


**Oops. Ignore that. I mis-read your post. A good desoldering iron will
do all you require.

Actually I usually try to cut pins on chips when I'm trying to isolate a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?

That's what I'd be using to tell when a voltage rail, or a signal line,
stops being adversly affected after the removal of the connection to an
offending component. In fact if I didn't have the 'scope or the
multimeter, I may not be able to determine which IC pins were potential
culprits.

--
__ __
#_ < |\| |< _#

 

[Computer Nerd Kev]

Benderthe.evilrobot <Benderthe.evilrobot@virginmedia.com> wrote:

"Computer Nerd Kev" <not@telling.you.invalid> wrote in message
newsc1661$1a28$1@gioia.aioe.org...
Phil Allison <pallison49@gmail.com> wrote:

** I need to remove some 16 pin DILs from a triple layer PCB ( ground
plane in the middle ) while not damaging them. So far, only pin cutting
and tedious removal of the each legs is working for me.

Do you have a trick for cutting the pins? I can never get any of my side
cutters in close enough.

The pressed (and hardened) steel Excellite cutters seem to do the job, or
you can set aside regular cutters that have been ground for a slimmer point.

You can shear the pins off most SMD chips with a Stanley knife - but you
have to be dead careful not to slice through and hit any tracks underneath.

I'd imagine a risk of peeling up the pad for that pin as well. I'll
keep that one in my "in emergency break glass" case of tips.

--
__ __
#_ < |\| |< _#

 

[Trevor Wilson]

On 8/04/2017 10:51 PM, ~misfit~ wrote:

Once upon a time on usenet Phil Allison wrote:
Actually I usually try to cut pins on chips when I'm trying to
isolate a fault and don't want to cut the PCB (or veroboard)
tracks. A bit of component lead is soldered over the break after
I'm satisfied. I have managed it sometimes, but with great
difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?


** Won't help if there is a short on a 5V DC supply rail with many
ICs and ceramic caps across it. Best way to find the culprit is to
use the "tune for maximum smoke" technique.

Apply a bench supply to the rail that has enough current to *smoke
out" out the cap or IC that is shorted.

Finds bad tantalums and ceramics in a couple of seconds, bad ICs may
be found with a finger test - AKA the "ouch" test.

Anyone who has serviced amplifiers using Hitachi TO3 mosfets in
parallel groups knows a finger test works to find any dead ones. Do I
need to explain?

FYI:

Hitachi TO3 mosfets have internal fuses that can isolate a bad device
during a short or other overload - the amp keeps working albeit at
somewhat reduced power capacity. Gotta love that.

Yep. I'm in the process of reconfiguring a pair of 100w mono amps that are
running two each J50 / K135 each to run on an extra +/- 15v (and doubling
the 2 x 10,000 uF of smoothing caps to 2 x 20,000 uF) and paralleling a
third pair of MOSFETs per amp (on small perfboard daughterboards and fly
leads), then building them both with their power supplies into a big
(re-purposed Perreaux PA amp) case and adding a couple speaker protection
modules.

They already sound really good with two pairs of devices each and +/- 60v
rails. They should sound awesome with three pairs and +/- 75v rails. <g

**They won't. If you think they do/will, then you need to get out a lot
more. Those old Hitachi MOSFETs, were very tough and ideally suited to
public address systems. For high quality audio, they suck.
Fundamentally, they are quite non-linear at anything under an Amp or so
of bias current. The negative tempco of gm means that any fast rising
transients and/or when using low impedance speakers will cause a severe
curtailing of dynamics.

I suggest you compare your MOSFET POS to an ancient Phase Linear 400 (or
700), or almost any other BJT amp. You will be stunned at how much
better the old PLs sound. Reliability, of course, is a different matter.
MOSFET amps tend to be very reliable, when properly designed. As an
example of very poor design, I refer you to the old and now defunct, NRG
(energy) brand of MOSFET amps. Extremely unstable designs.

--
Trevor Wilson
www.rageaudio.com.au

 

[Tony]

On 09-Apr-17 1:07 AM, Benderthe.evilrobot wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:a79ee72b-ee65-49f2-bd28-5646558a8b07@googlegroups.com...


Actually I usually try to cut pins on chips when I'm trying to
isolate > a
fault and don't want to cut the PCB (or veroboard) tracks. A bit of
component lead is soldered over the break after I'm satisfied. I have
managed it sometimes, but with great difficulty.

That is a very crude method of fault finding, do you not own a 'scope
and a good multimeter?


** Won't help if there is a short on a 5V DC supply rail with many ICs
and ceramic caps across it. Best way to find the culprit is to use the
"tune for maximum smoke" technique.

Apply a bench supply to the rail that has enough current to *smoke
out" out the cap or IC that is shorted.

With a shorted ceramic cap - the smoke could come from a narrow section
of PCB supply track.

The method isn't without its merits though.

It's quite simple. If you have power planes Phil's way the only way I
know. If your power is routed you apply a reasonably high current and
probe the voltage drop, which will lead you to the short.

 

[Phil Allison]

Trevor Wilson wrote:

They already sound really good with two pairs of devices each and +/- 60v
rails. They should sound awesome with three pairs and +/- 75v rails. <g


**They won't. If you think they do/will, then you need to get out a lot
more. Those old Hitachi MOSFETs, were very tough and ideally suited to
public address systems. For high quality audio, they suck.

** TW has been pushing this line of *complete bollocks* for decades.

He had a strong commercial motive - he sells expensive Hi-Fi amplifiers ( ME brand) that used BJTs.

Fundamentally, they are quite non-linear at anything under an Amp or so
of bias current. The negative tempco of gm means that any fast rising
transients and/or when using low impedance speakers will cause a severe
curtailing of dynamics.

** Utter horse poo.

No such misbehaviour exists with Lateral mosfets used in any real power AMPLIFER in source follower mode.



..... Phil

 

[keithr0]

On 4/9/2017 3:19 AM, Benderthe.evilrobot wrote:

"keithr0" <user@account.invalid> wrote in message
news:ekr66uFab3pU1@mid.individual.net...
On 4/8/2017 8:17 AM, Clocky wrote:
On 8/04/2017 4:35 AM, Benderthe.evilrobot wrote:

"Sylvia Else" <sylvia@not.at.this.address> wrote in message
news:ekes48Frr3qU1@mid.individual.net...
https://www.jaycar.com.au/plastic-desolder-tool/p/TH1860

This is unsafe. It self-disassembles in use, projecting the handle
sharply upwards towards any vulnerable body part, with the eyes being
the most obvious targets.

Almost all the plastic body solder pumps I've had were crap.

Years ago I found a turned aluminium one in a tool box someone
dumped at
the recycling place.

Its pretty good - but I can't find any markings to identify the
manufacturer.

Does it look like this?

https://tronixstuff.files.wordpress.com/2012/09/suckersmall.jpg

I think I still have the one I bought from Tandy 30-odd years ago
somewhere, not that it was any good.


None of them are, the best method is solder wick, used properly it
will leave everything just as new. When I worked for NASA, it was the
only approved method of de-soldering.

Multilayer boards do heatsinking too well - solder wick can get stuck on
and make it too easy to pull tracks off.

Just learn how to do it properly, multi layer boards with power and
ground planes are difficult by any method.

 

[Phil Allison]

Trevor Wilson wrote:

**They won't. If you think they do/will, then you need to get out a lot
more. Those old Hitachi MOSFETs, were very tough and ideally suited to
public address systems. For high quality audio, they suck.


** TW has been pushing this line of *complete bollocks* for decades.

He had a strong commercial motive - he sells expensive Hi-Fi
amplifiers ( ME brand) that used BJTs.


**You may care to note that I suggested a comparison with an old Phase
Linear amp.

** GAINT Yawnnnnnn .....

Wot a crock of context shifting BULLSHIT !!!!

No mention of ME.

** It's all - me, me, me.

Dear Trev.

Having worked on some modern Perreaux amps,

** More context shifting CRAP.

TW is a charlatan, not a tech.

I am pleased to say that
they do not use the horrible old Hitachi MOSFETs and sound much better
than the old things.

** Just another of TW's insane thoughts presented as fact.

Just like all his AGW shite.

The narcissistic idiot thinks he thinks.

ROTFLMAO ....

**I serviced every single one of the tiny number of NRG amps that made
it to Australia. They all blew up. Several times. Worse, when one
channel went, I suspect some kind of oscillation was set up, which took
out the other channel. Every single MOSFET failed. I was never able to
ascertain why the amps failed, just that they did, with monotonous
regularity.

BTW: The MOSFETs were not Hitachi types.

** TW needs to visit a psychiatric hospital - for his own benefit.

And stay there, for our benefit.




..... Phil