9 May
2011
9 May
'11
5:40 a.m.
Desoldering a component is a learned skill. I have been
in component level repair since the early to mid 1960's.
I was trained for depot repair level by the USN.
On normal track devices, DIPs, transistors, diodes, etc
I rarely go above 650*. If the component has a large
back plane of tracking on either side of the board, I will
dial up to 750*.
As Phil mentioned, a first attack to remove what oxidation
and junk is present, is appropriate. Then I will apply some
new solder, and watch closely for the "drop" of the new solder
which means it has heated thru the hole to the far side. Both
the internal plating of the through hole and the pin help
convey the heat. Very inexpensive boards with no thru plating
will be your enemy. I would not expect to find that in a PDP.
An immediate application of a good vacuum to remove the solder
is then warranted. If your vacuum device will not pull a vacuum
against the area of skin on the outside of your hand between
your thumb and forefinger, get another, it is NOT good enough.
Follow that with a dental probe to manipulate the desoldered
pin if possible, examining both sides of the board. You may
hear or feel a "click" as the last solder whisker lets go.
I have never used "braid", I have never liked it, you must heat
both the braid and the track/pin to melt temperature, difficult
at best. A product called, I believe "Solda-Quik", used in surface
mount work, can be used as a catalyst to lower the melt temperature
of some solders to around 350* and aid in the more rapid removal
of the existing solder. I have done surface mount repair with
this product.
A lifted track can be repaired with some 30 gauge wire wrap wire
stripped clean, bridging gaps, or thru holes to solid track on both
sides. I have also socketed any DIP I have ever removed, if at all
possible, with a good 2 side wipe socket suck as AMP.
Kevin Andres
Senior Technician
Engineered Protection Systems Inc
Nicet # 90660
Fire Alarm Systems Level II
616 459 0281
kandres at epssecurity.com
epssecurity.com
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf
Of cctech-request at classiccmp.org
Sent: Saturday, May 07, 2011 1:00 PM
To: cctech at classiccmp.org
Subject: cctech Digest, Vol 93, Issue 8
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Today's Topics:
1. Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
(Zane H. Healy)
2. Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
(Fran Smith)
3. Re: rack mounting vintage gear (Jonas Otter)
4. Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
(Pontus)
5. Desoldering a chopper transistor (Rob Jarratt)
6. Re: Desoldering a chopper transistor (Pete Turnbull)
----------------------------------------------------------------------
Message: 1
Date: Fri, 6 May 2011 12:38:59 -0700
From: "Zane H. Healy" <healyzh at aracnet.com>
Subject: Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>, General Discussion:
Message-ID: <p0624085bc9e9fe44266a(a)[192.168.1.157]>
Content-Type: text/plain; charset="us-ascii" ; format="flowed"
At 12:24 PM -0400 5/6/11, Dave McGuire wrote:
On 5/6/11 12:16 PM, Richard wrote:
I have a MicroVAX III, nice system. What might be interesting to
know is what it has for a disk subsystem. If they upgraded the CPU's
and RAM, did the also upgrade the hard drives to something other than
MFM?
In any case I'd say $250 for a KA650 system in a BA123 is well worth
the cost, at least it is if you're local. I wouldn't want to have to
pay shipping on it!
Zane
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh at aracnet.com | OpenVMS Enthusiast |
| | Photographer |
+----------------------------------+----------------------------+
| My flickr Photostream |
| http://www.flickr.com/photos/33848088 at N03/ |
------------------------------
Message: 2
Date: Fri, 06 May 2011 13:11:26 -0400
From: Fran Smith <fsmith at ladylinux.com>
Subject: Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
To: cctalk at classiccmp.org
Message-ID: <4DC42BBE.8080003 at ladylinux.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hiya,
See item # 170637016956
Described as a "VAXstation 3", but I don't think that's the proper
designation.
That could very well be a VAXstation-3. If it was sold as a
VAXstation-II and upgraded with a KA650 CPU and MS650 memory
module(s), that'd be an appropriate designation.
In any event, that one (he says he has two) is in the BA123 "World
Box", which have dried up significantly on the market in the past
couple of years and are becoming much harder to find than they had
been. That could very well be a VAXstation-3. If it was
sold as a
VAXstation-II and upgraded with a KA650 CPU and MS650 memory module(s),
that'd be an appropriate designation.
I had one just like this back in the day with full graphics , mouse etc
that I used as a workstation. I upgraded it from MV-11 to MV-III in box
with the above kit.
Nice versatile units and I hope they go somewhere they can be used.
Fran
------------------------------
Message: 3
Date: Fri, 06 May 2011 20:09:02 +0200
From: Jonas Otter <jonas at otter.se>
Subject: Re: rack mounting vintage gear
To: cctalk at classiccmp.org
Message-ID: <4DC4393E.3010304 at otter.se>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> What exaclty is an "anti-tip
feature"?
Most racks have a pull out stabilizer of some kind,
or even jutting out little "feet" to prevent them> from tipping over
forwards while you pull heavy things out on the rails. So, in order to pull out a
device, first you pull out the anti-tip bar at the bottom, then pull out the device. The
DEC H960
racks don't have that pull-out bar, instead they have two feet that stick out the
front of the
cabinet a foot or so, and serve to trip people walking too close to the computer...
-Ian
You can see an anti-tip bar here:http://www.flickr.com/photos/textfiles/3789164168/
If you look at the bottom of the rightmost TU80 you can see a silvery T-shaped thing with
a foot on it. That is the anti-tip bar.
/Jonas
------------------------------
Message: 4
Date: Fri, 06 May 2011 22:34:20 +0200
From: Pontus <pontus at update.uu.se>
Subject: Re: ebay: VAXstations (Salt Lake City; I can pick up for you)
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Message-ID: <4DC45B4C.6070803 at update.uu.se>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
2011-05-06 18:24, Dave McGuire skrev:
In any event, that one (he says he has two) is in the BA123 "World
Box", which have dried up significantly on the market in the past
couple of years and are becoming much harder to find than they had been.
It is definitely on the want list :) If anyone local to me (sweden that
is) has anything in a BA123 I wouldn't mind driving a bit and pay a bit
for it.
I've seen two in Sweden, on with GPX
Regards,
Pontus.
------------------------------
Message: 5
Date: Sat, 7 May 2011 10:04:40 +0100
From: "Rob Jarratt" <robert.jarratt at ntlworld.com>
Subject: Desoldering a chopper transistor
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Message-ID: <037a01cc0c95$ce2121c0$6a636540$(a)ntlworld.com>
Content-Type: text/plain; charset="US-ASCII"
I need to desolder a chopper transistor from a PCB in the PSU of my PDP11 so
that I can test it and if necessary replace it. The trouble is that I am not
experienced with soldering and desoldering and I am having a lot of trouble
desoldering it. I have made several attempts, damaging one of the PCB tracks
in the process (should be repairable by adding a wire). I have a cheap
Weller 40W soldering iron and I have been using some narrow tips. I have one
of those pumps for sucking out the molten solder. I also have 2mm solder
wick (braid?).
I seem to have removed most of the solder from two of the pins, mostly with
the pump, the solder wick just does not seem to pick up any solder not
matter what I do. One of the pins, however, goes onto a track that is more
like a large area of metal and the iron does not even seem to melt the
solder there.
The thing I really don't understand is how you desolder more than one pin at
the same time. There is always bound to be just a little solder left holding
each pin in place no matter how much you remove with the pump or wick. So
it seems to me that you would need to have the solder in all 3 pin holes
molten, all at the same time, to be able to lift the component.
What is the trick? Or is it just that my soldering iron is not good
(powerful) enough?
Thanks
Rob
------------------------------
Message: 6
Date: Sat, 07 May 2011 10:40:55 +0100
From: Pete Turnbull <pete at dunnington.plus.com>
Subject: Re: Desoldering a chopper transistor
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Message-ID: <4DC513A7.3000405 at dunnington.plus.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 07/05/2011 10:04, Rob Jarratt wrote:
I need to desolder a chopper transistor from a PCB in
the PSU of my PDP11 so
that I can test it and if necessary replace it. The trouble is that I am not
experienced with soldering and desoldering and I am having a lot of trouble
desoldering it. I have made several attempts, damaging one of the PCB tracks
in the process (should be repairable by adding a wire). I have a cheap
Weller 40W soldering iron and I have been using some narrow tips. I have one
of those pumps for sucking out the molten solder. I also have 2mm solder
wick (braid?).
You don't normally desolder more than one pin at a time but you do need
a good iron and a good pump. On DEC PSUs particularly, I've found the
holes are, um, less than generous -- the component pins tend to be a
close fit and there's not much room around the pin even when you get all
the solder out.
I normally use a 100W Weller soldering gun for things like those
trannies (I have a 50W Weller temperature-controlled iron for anything
else). The trick is to get the solder hot enough to flow, and to do so
quickly. If you can't do that, you're unlike to succeed, and the longer
you leave the heat on the pad, the more likely you are to damage
something. Then use a large pump to suck it off. Sometimes adding
fresh solder and trying a second time helps -- the first attempt removes
most of the oxidised stuff and the flux from the fresh solder helps
remove the last of it. Then push the pin from side to side to break the
last whisker of solder that bridges from the pad across the gap to the
pin -- if you can!
I'd suggest getting a bigger iron if you can, and don't use a narrow tip
for large components. I wouldn't waste any time on solder braid, either
-- fine for small stuff but probably not for this.
--
Pete Peter Turnbull
Network Manager
University of York
End of cctech Digest, Vol 93, Issue 8
*************************************
9 May
9 May
8:16 a.m.
On Mon, May 09, 2011 at 08:40:56AM -0400, Kevin Andres wrote:
Desoldering a component is a learned skill. I have been
..
As Phil mentioned, a first attack to remove what
oxidation
and junk is present, is appropriate. Then I will apply some
new solder, and watch closely for the "drop" of the new solder
Follow that with a dental probe to manipulate the
desoldered
A large sewing needle will do as well, or a small jewelers screwdriver.
A lifted track can be repaired with some 30 gauge wire
wrap wire
stripped clean, bridging gaps, or thru holes to solid track on both
Don't forget to superglue the wire to the board on longer runs to keep
the wire from flopping about. These were always called barnacles around here.
- Diane
--
- db at FreeBSD.org db at db.net http://www.db.net/~db
Why leave money to our children if we don't leave them the Earth?
12:45 p.m.
[...]
convey the heat. Very inexpensive boards with no thru
plating=20
will be your enemy. I would not expect to find that in a PDP.
The advantage of no through plating is that its vairly easy to get all
the solder off (it will not remain in the hole, holding the component
lead to the sides of the hole). On the other hand, it's a lot easier to
lift tracks on such a board.
I think all the PCBs in a PDP11 are going to be through plated. It;'s
been some time since I've worked on the PSU in question (H7140), but I am
pretty sure the PCBs I repaired in mine were through plated.
[...]
I have never used "braid", I have never
liked it, you must heat
Like you I've never got on with braid for desoldering through-hole parts.
I have a reel in my toolikt though for some SMD repairs. It's useful for
removign bridges between pins on SOICs and PQFPs. Actually, a lot of the
ime, braid works well for desoldering such devices for removal.
[...]
A lifted track can be repaired with some 30 gauge wire
wrap wire
stripped clean, bridging gaps, or thru holes to solid track on both
That's fine for logic signal tracks, but for tracks carrying a higher
current (for example inside the PSU), I'd use thicker wire.
I am told taht for the highest reliability you should solder the wire to
a component lead, via, or similar., and not just put it across the break
and solder it to the track. That said, I have never found the latter
method partciularly unreliable (by that I mean that I have repaired PCBs
that way and nevre had problems from the repair going open-circuit).
What does NOT work is to but a blob of colder across the break.
sides. I have also socketed any DIP I have ever
removed, if at all
possible, with a good 2 side wipe socket suck as AMP.=20
I prefer turned-pin (machined pin) sockets. I don;t think I've evr had a
bad contact in one of those.
I;ll socket any 'expensive' or programemd device (EPROM, PAL, etc) that
I've removed. But I generalyl solder TTL, 4000-series CMOS, etc,
directly to the PCB. The on exception is on something that I am designing
(where I socket everything), it's a lot easier to debug a circuit if you
cna pull one of the ICs and inject suitble signals on the socket contacts.
-tony
4928
days inactive
4928
days old
2 comments
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ard＠p850ug1.demon.co.uk -
db＠db.net -
kandres＠epssecurity.com