>From: ard at p850ug1.demon.co.uk
>> No, even the tube may be revived some. You can
>> often run the heater at a higher voltage for some
>> time and check the emission periodically. Usually,
>> you can safely run the filament at 1.5 to 2 times
>> the rated voltage for 5 or 6 hours. It is usually
>The method generally used on TV tubes of the period (and I don't see why
>monitor tubes would be any different) was something like :
>1) Over-run the heater. Typically a 6.3V heater would be run at 8V or 10V
>2) Apply a fairly high (200V-ish) +ve voltage the control grid (wrt the
>cathode), all other electrodes floating (no EHT applied either).
I've had better luck with 0 volts. If the tube has not been used
for a long time, it will be a little gassy. This tends to boil
off the cathode along with the other stuff. When you have the voltage,
the electrons will hit the gass atoms and ionize them. These are
then slammed back into the cathode. One article I read stated
that the first stage should be done with 0 volts and then switch
to a + volts on the grid(s)+anode for the last part.
I've not tried this myself but the method makes sense. In the
first part, the getter has time to catch the outgassing. The
last part helps to freshen the surface.
I know that there are many articles that state to put the voltage
on from the beginning. I've also read in a only a couple of
articles that the outgassing from the initial stages can poison
the cathode enough to make the process useless. I recover
many old vacuum tubes for my old battery radios. I've had
good enough experience with the 0 volts and enough bad
experience with the voltage on the grid/plate that I use
the 0 volt.
>This, combined with the overheated cathode, stripped the top layer of
>emissive stuff off the cathode, hopefully exposing a fresh surface. It
>worked will on some CRTs, on others, it totally removed the emissive
>material and you ended up with a totally useless CRT. But you've nothing
>to lose by trying it on an otherwise useless tube
>There was also a simple way to do an emission test. Again the only
>electrodes you used were the heater, cathode, and control grid. I think
>you ran the heater at the normal voltage and used the cathode/grid as a
>diode and measured the current flow with a fairly low (if any) +ve
>voltage on the grid. The higher the current, the better the cathode was
>Many designs for such devices have been published in the magazines. The
>lethal ones get the 300V or so by rectifying the mains (or in your case
>using a voltage doubler on the mains). More friendly ones used an
>isolating transformer or a oscillator/step up transformer from a battery.
No, even the tube may be revived some. You can
often run the heater at a higher voltage for some
time and check the emission periodically. Usually,
you can safely run the filament at 1.5 to 2 times
the rated voltage for 5 or 6 hours. It is usually
done with no cathode current while at the higher
voltage and then return to normal levels to check
for the current. It would help to have a tube
tester but I suspect that just measuring the voltage
drop across a resistor in the cathode circuit
someplace would tell if there was any improvement.
You graph the increase in current. At some time,
you don't get any improvement so you stop there.
No sense wasting the filament.
You could control the voltage with a variac
and a transformer.
Do make sure that the tube is the cause. Raised
voltage on the filament can shorten the life of
the filament and at times cause cathode to
If the image is well focused and not over sized,
the main rail voltages are OK.
>From: "Richard" <legalize at xmission.com>
>In article <200601311927.LAA29559 at ca2h0430.amd.com>,
> "Dwight Elvey" <dwight.elvey at amd.com> writes:
>> >[...] I do have one monitor. I haven't tried
>> >to power it up, but written on the case is the word "DIM", presumably
>> >identifying a failure in the monitor somewhere. I've never repaired
>> >monitors, so I'm not sure what a dim image is suppose to indicate.
>> >Failing HV drive circuitry?
>> HV would cause blooming of the image. Dim image is weak cathode
>> in the tube or problems in the circuits controlling the cathode
>> to gate voltage levels.
>So... if its the tube, there's nothing to do but replace the tube?
>Egads... I wonder how hard it would be to find a compatible
>"The Direct3D Graphics Pipeline"-- code samples, sample chapter, FAQ:
> Pilgrimage: Utah's annual demoparty
A normal PC board DOES NOT have a nickel plate under the tin/lead. I
suspect you are thinking about PC boards that have been gold plated, and
yes, those do have a nickel underplate.
> From: "Dwight Elvey" <dwight.elvey at amd.com>
> Normally the PC board will have a thin layer of
> nickel over the copper before the solder. This also
> produces a blue-ish green oxide.
A lot of nice radio/test/computer equipment from the late 70's through
the 80's and even the early 90's had the "feature" of battery-backed-up
configuration settings. Often this was done thorugh NiCads soldered to
the PC board (often in those little plastic modules). Over the years,
the NiCads have usually leaked out their gunk (if not liquid, then
fumes?) which has gone on to attack the PC boards and
components/sockets around it. All the originally shiny metal now has a
layer of white or white/green deposits over it.
My primitive chemical understanding is that something-hydroxide
(calcium hydroxide, sodium hydroxide?) from the battery gets out (if
not as a liquid, then as a vapor) which is a base. This corrodes the
metal surfaces around the battery.
In my most recent escapade, I took such a board and put it in some
dilute acetic acid (think "vinegar" except I was using some photo
chemicals and I probably had the concentration stronger than the
grocery store vinegar). The deposits turn even greener (in some cases
bluer but maybe that was the indicator in the stop bath). Using a
plastic brush I scrub away these deposits, but this does not result in
a shiny clean PC board.
Again, my primitive chemical understanding: the acid combines with the
base whatevery-hydroxide and what we're left with salts.
Rinsing in water and repeating does help get off more of the gunk but
it's never all gone. In any event, I've at least slowed (maybe stopped)
damage to the PC board, and after drying off I find it still works - in
some cases works better because we don't have all the gunk anymore.
When I see the gunk I see it mostly as an insulator that will stop
conductivity, but of course it also bridges together traces and
probably gives very real leakage in some cases too. Incidentally in
many cases the board doesn't work right until it is really really dry,
so I think that in some cases just the leakage due to the rinse water
is enough to inhibit normal operation.
But now, say I want to remove a somewhat corroded IC socket off the
board because I suspect it's causing problems. I put my soldering iron
on the pad and try to heat up and melt the solder. I heat, and heat,
and heat, but nothing's melting! Check that the soldering iron is
working and that the tip isn't covered with crud... well, maybe there
was some crud but after wiping it off the soldering iron is working
So I go in with a wire brush and an X-acto knife and try getting past
whatever chemical is still covering the pads and traces, and find it's
really tough stuff. The wire brush works but it also erodes the traces.
The X-acto knife works somewhat on pads with solder on 'em. After
repeated attacks, though, the solder still doesn't really want to melt.
I try putting on some new solder thinking that the rosin and new new
metal will help, but all it does is ball up and roll off.
So what I'm left with is a PC board that is somewhat/mostly working but
in cosmetically poor shape, and feeling that I should do more. What's
semi-ironic about all this is that the board usually doesn't have any
more than $10 worth of parts on it but an instrument that cost $10K
twenty years ago (and is maybe worth $1K today on the used market) is
dependent on this still crud-covered PC board that I can't even fix the
Buying a replacement PC board is usually out of the question because
they haven't made this doohickey in 20 years, and all the boards out
there all have NiCad leakage damage on them.
One solution would be to lay out a clone PC board that never had the
NiCad damage done to it and stuff it with new parts. Realistically in
some cases this would take less time to do than I've already spent
cleaning/rinsing/drying/attempting to solder on the existing board.
But is there some magic chemical or mechanical means that will render
the existing cruddy PC board solderable so I can replace these flaky
As a note, Muriatic acid is hydrochloric acid.
>From: "Marvin Johnston" <marvin at rain.org>
>When cleaning PC Boards that have had battery leakage, I always use
>Muriatic Acid (about 33% Hydrochloric Acid) also known as pool acid for
>adjusting pool pH. When I still owned the Printed Circuit shop, I would
>use something called Solder Brite to remove the oxidation on the boards
>after etching and prior to reflow. If you have a PC shop close by, you
>might stop by and see if they would give you a couple of ounces to try.
>IIRC, Solder Brite was basically Muriatic acid with some additives.
>BTW, when I am cleaning up the crud on PC boards, I only use a couple of
>*drops* of Muriatic acid and I would guess that Solder Brite could be
>used the same way. Once it stops foaming, I am done :).
>> From: "Tim Shoppa" <tshoppa at wmata.com>
>> But is there some magic chemical or mechanical means that will render
>> the existing cruddy PC board solderable so I can replace these flaky
When cleaning PC Boards that have had battery leakage, I always use
Muriatic Acid (about 33% Hydrochloric Acid) also known as pool acid for
adjusting pool pH. When I still owned the Printed Circuit shop, I would
use something called Solder Brite to remove the oxidation on the boards
after etching and prior to reflow. If you have a PC shop close by, you
might stop by and see if they would give you a couple of ounces to try.
IIRC, Solder Brite was basically Muriatic acid with some additives.
BTW, when I am cleaning up the crud on PC boards, I only use a couple of
*drops* of Muriatic acid and I would guess that Solder Brite could be
used the same way. Once it stops foaming, I am done :).
> From: "Tim Shoppa" <tshoppa at wmata.com>
> But is there some magic chemical or mechanical means that will render
> the existing cruddy PC board solderable so I can replace these flaky
Normally the PC board will have a thin layer of
nickel over the copper before the solder. This also
produces a blue-ish green oxide.
The dark brown to black is the copper oxides and salts.
It can be removed with acid and/or mechanical rubbing.
If using any acid that does not evaporate, it needs
to be neutralized.
If you can't find something to use, two part radiator
cleaner should do the job. They normally use oxalic
acid so handle as a toxic substance and use gloves
and face shield. I've not tried this but it should
work. You may need to heat the bath.
One thing to consider. If it is a location the will
see high temperatures ( on the order of 100C ) during
operation, a copper to solder joint will fail with
high resistance. This is one of the reasons they put
on the nickel layer(see note). For most locations, the
temperature thing is not an issue but near regulators
and other power devices, you'll need to restore the nickel
Note: The nickel layer also simplifies the PC processing.
>From: "Joe R." <rigdonj at cfl.rr.com>
>>On 2/1/2006 at 9:34 AM Tim Shoppa wrote:
>>>But is there some magic chemical or mechanical means that will render
>>>the existing cruddy PC board solderable so I can replace these flaky
> I've seen the stuff you're talking about. Even after you clean off the
>blue-green corrision the copper is black and solder won't stick to it. I
>expect the black is due to copper oxide. You need to remove it by treating
>it with some kind of acid that will form a water soluable salt with copper.
>I expect dilute sulfuric acid may be the best. That's what they use to
>clean copper circuit boards prior to assembly as well as copper items
>prior to electroplating, etc. I'm sure you're aware of the dangers of
>sulfuric acid and how much damage it can do to the board and components so
Still, at .10 a bandsaw makes a universal socket
>From: "J.C. Wren" <jcwren at jcwren.com>
>No, definitely .4". 2 pins will fit equally spaced between the two
>rows, and if you mentally swing 4 pins 90 degrees, you can visualize the
>Ethan Dicks wrote:
>> On 2/1/06, J.C. Wren <jcwren at jcwren.com> wrote:
>>> You're doing unnatural things to those pins to get them to fit in a .4"
>>> socket. At least, all my 22V10s are 0.3" wide...