Repair of the power board from an HP DeskJet, damaged by lea

P

Peter Easthope

Guest
Hello again,

Photo here of the power board from an HP DeskJet printer.
http://members.shaw.ca/peasthope/DeskJetPowerBoard.jpg

This is the back of the board.
http://members.shaw.ca/peasthope/DeskJetPowerBoardBack.jpg

I removed the three medium sized capacitors in the upper
left and, not surprisingly, found residue with the appearance
of thinned molasses beneath them.

The photo of the back side shows where this residue has flowed
through some of the holes and corroded along traces.

I've never tackled anything this badly damaged. Cleaning
exposed surfaces with swabs and alcohol won't help the corrosion
in the holes and under the green polymer coating. What are the
recommendations? Is repair a realistic possibility? If so,
pointers about technique will help.

Thanks, ... Peter E.
 
On 6/8/2012 6:23 PM, Peter Easthope wrote:
Hello again,

Photo here of the power board from an HP DeskJet printer.
http://members.shaw.ca/peasthope/DeskJetPowerBoard.jpg

This is the back of the board.
http://members.shaw.ca/peasthope/DeskJetPowerBoardBack.jpg

I removed the three medium sized capacitors in the upper
left and, not surprisingly, found residue with the appearance
of thinned molasses beneath them.

The photo of the back side shows where this residue has flowed
through some of the holes and corroded along traces.

I've never tackled anything this badly damaged. Cleaning
exposed surfaces with swabs and alcohol won't help the corrosion
in the holes and under the green polymer coating. What are the
recommendations? Is repair a realistic possibility? If so,
pointers about technique will help.

Thanks, ... Peter E.
Click to expand...
Looks like a trivial wiring problem to me.
Be glad it's not a 10 layer SMT board with tiny feedthrus everywhere.
Try a solvent like Simple Green as well as alcohol.
They dissolve different stuff.
Scrub it several times with each. Then take a wire brush to it.
You're gonna rewire the traces anyway.
Dry it well...then dry it some more.
 
"Peter Easthope"
Photo here of the power board from an HP DeskJet printer.
http://members.shaw.ca/peasthope/DeskJetPowerBoard.jpg

This is the back of the board.
http://members.shaw.ca/peasthope/DeskJetPowerBoardBack.jpg

I removed the three medium sized capacitors in the upper
left and, not surprisingly, found residue with the appearance
of thinned molasses beneath them.

The photo of the back side shows where this residue has flowed
through some of the holes and corroded along traces.

I've never tackled anything this badly damaged. Cleaning
exposed surfaces with swabs and alcohol won't help the corrosion
in the holes and under the green polymer coating. What are the
recommendations? Is repair a realistic possibility? If so,
pointers about technique will help.
Click to expand...

** I have repaired many PCBs that were the victims of electrolyte leakage -
do the obvious, replace copper tracks that show corrosion with wire links
and bits of plastic covered wire.

Wash the area with a good PCB cleaner spray and/or de-natured alcohol -
watch out for places where the electrolyte can hide like down component
holes and under ICs etc. Dry thoroughly with hot air.

Long as the circuitry is not highly sensitive to PCB leakage, it should be
fine.


.... Phil
 
On Fri, 8 Jun 2012 18:23:31 -0700 (PDT), Peter Easthope
<peasthope@shaw.ca> wrote:

I've never tackled anything this badly damaged. Cleaning
exposed surfaces with swabs and alcohol won't help the corrosion
in the holes and under the green polymer coating. What are the
recommendations? Is repair a realistic possibility? If so,
pointers about technique will help.
Click to expand...
As others have mentioned, just clean up the mess with your favored
cleaner. Then tin what's left of the traces with plenty of solder. If
there's little copper left, run a bare wire over the traces, and
solder the bare wire to the traces. The bare wire should be about #20
AWG to avoid turning it into a fuse. Bigger wire is fine. If the
copper tries to detach from the PCB, do the bare wire trick, and then
bury it under some acrylic or urethane conformal coating to stick it
to the board. Don't worry about what it looks like as you're the only
person that will ever see the work.

You might also check the remaining capacitors with an ESR tester. Just
because the look good, doesn't mean they are good.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
Peter Easthope wrote:

On Friday, June 8, 2012 8:25:14 PM UTC-7, Jeff Liebermann wrote:

You might also check the remaining capacitors with an ESR tester.
Just because the look good, doesn't mean they are good.


Do you always disconnect the cap for measuring ESR? I've seen
a mention of checking the ESR of an installed capacitor.

Thanks, ... Peter E.


Doing in circuit testing only works if you have a tool that operates
Click to expand...
at low voltage at the test point, one that is below diode drop voltages.

These days, diode drops are in the ~.295 volt area.. So the test
device must be presenting voltages below that to get a fair assessment of
the cap, while in circuit. Also, it makes sense to make sure any test
gear you use does not present a voltage to the circuit above that level,
otherwise, you could damage sensitive components, just testing them.

THe last time I looked, 100 mv. was a good area...

When expecting low ESR readings on a cap, it's pretty much straight
forward, doing in circuit test. Because the value to be expected would
be low to start with. Circuit paths away from that area are more than
likely going to register more.

There are times when in circuit testing fails the ESR test with a
tester that is designed for low voltage sampling.

If you are testing for dielectric break down (voltage ratings), then
yes, you most likely will need to extract the cap.

Jamie
 
On Sun, 10 Jun 2012 12:32:00 -0700 (PDT), Peter Easthope
<peasthope@shaw.ca> wrote:

On Friday, June 8, 2012 8:25:14 PM UTC-7, Jeff Liebermann wrote:
You might also check the remaining capacitors with an ESR tester.
Just because the look good, doesn't mean they are good.

Do you always disconnect the cap for measuring ESR? I've seen
a mention of checking the ESR of an installed capacitor.
Click to expand...
No. I measure them in the circuit. This works because the ESR of the
caps, even when there are a string in parallel, is much less than the
conduction resistance of most active devices that are likely to be in
parallel with the caps.

I have this ESR tester:
<http://www.flippers.com/esrkthnt.html>
<http://members.ozemail.com.au/~bobpar/esrmeter.htm>
in addition to several home made contraptions. Since I don't need to
check batteries with the tester, I have a pair of back to back 1N4002
diodes across the test leads to deal with charged cazapitors.

What's critical is knowing what the value should be. I have a chart
that helps (borrowed from Bob Parker's web site):
<http://802.11junk.com/jeffl/crud/ESR.txt>
Since I have a fairly good collection of replacement caps, I also like
to compare values with a brand new cap.

Since the major effort involved in recapping is often extracting the
board from its overly protective enclosure, I tend to replace first,
and test later. If one cap, of a specific type and value is obviously
bad, it's highly likely that all the caps of that type and value are
also bad. So, I replace all the likely culprits, and not worry about
testing.

Please note that it's not just the big caps, which tend to experience
high ripple current heating, that die. The smaller electrolytic have
their share of problems, especially in switching power supplies. These
are never visibly bulging and must be tested with an ESR tester.

There's also running assumption that the bulging capacitors are
somehow defective. That was true when various manufactories were
shipping electrolytics with bogus electrolyte about 14 years ago.
That's no longer the case and those caps are (hopefully) long gone.
What replaces them is marginal design and planned self destruction. In
order to save a few pennies, many manufacturers reduce capacitor
values and voltages to their absolute minimum. If there are three
caps in a row, and it will work with two caps, it's shipped with two.
The result is that the theoretical capacitor life, which is a function
of temperature and ripple current (causing internal heating), moves
fairly close to the desired lifetime. If the factory offers a 3 year
warranty, designing for a 6 year life is fairly common. The actual
failures will occur along a bell shaped curve, but the average will be
about 6 years. This is why I like to replace capacitors with the next
higher voltage rating. The ESR is actually higher, but the lifetime
is much longer.
<http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx>
<http://en.wikipedia.org/wiki/Electrolytic_capacitor#Reliability_and_length_of_life>

When I want the board to work forever (such as for my own equipment) I
try to use tantalum or polymer caps in place of electrolytics. They're
not suitable for every application and not available in every
capacitance and voltage rating, so be sure to think about what's
important in the circuit.
<http://www.capacitorlab.com/capacitor-types-polymer/>

Then, there's idiot error:
<http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
I replaced all the electrolytics in the picture, and couldn't
understand why they would blow up after about an hour of operation.
When I posted the question to this newsgroup, it was pointed out that
they were all installed backwards. (Thanks Phil A.)

Now, I have a question. Is this unspecified model Deskjet worth
repairing? Even when working perfectly, the print speed, reliability,
quality, and cost per page are all problematic when compared to a
laser printer. The only thing good about an inkjet printer is the
initial cost, which is less than a laser and the power consumption.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Friday, June 8, 2012 8:25:14 PM UTC-7, Jeff Liebermann wrote:
You might also check the remaining capacitors with an ESR tester.
Just because the look good, doesn't mean they are good.
Click to expand...
Do you always disconnect the cap for measuring ESR? I've seen
a mention of checking the ESR of an installed capacitor.

Thanks, ... Peter E.
 
On Jun 8, 8:25 pm , Jeff Liebermann <je...@cruzio.com> wrote:
As others have mentioned, just clean up the mess with your favored
cleaner. Then tin what's left of the traces with plenty of solder.
Click to expand...
Presumably traces are blackened where the electrolyte has corroded
between the board and the trace and between the polymer coating
and the trace. I should clean all the blackened sections completely
from
the board? Any clever means of cleaning out the holes in the board?

On Jun 10, 1:41 pm, Jeff Liebermann <je...@cruzio.com> wrote:
I have this ESR tester:
http://www.flippers.com/esrkthnt.html
http://members.ozemail.com.au/~bobpar/esrmeter.htm
Click to expand...
Same or similar here; the date label has "7/24/09".

Now, I have a question.  Is this unspecified model Deskjet worth
repairing?  Even when working perfectly, the print speed, reliability,
quality, and cost per page are all problematic when compared to a
laser printer.  The only thing good about an inkjet printer is the
initial cost, which is less than a laser and the power consumption.
Click to expand...
By simple financial calculation, probably not worth saving. But I
have
three DeskJets. Aside from power boards they are in good shape and
I have a lifetime supply of ink. So with my aversion to waste,
scrapping
them is difficult.

Thanks to everyone for the instructions, ... Peter E.
 
On Fri, 15 Jun 2012 13:25:56 -0700 (PDT), Peter Easthope
<peasthope@shaw.ca> wrote:

Any clever means of cleaning out the holes in the board?
Click to expand...
Slop cleaner all over the board. Let soak for about a minute. Blow
the cleaner THROUGH the holes in the board with compressed air (from
an air compressor, not canned air). If desperate, shove a needle or
wire through the holes. When you're done, use the compressed air to
blow out any liquid that might be hiding under parts.

Now, I have a question.  Is this unspecified model Deskjet worth
repairing?

By simple financial calculation, probably not worth saving. But I
have
three DeskJets. Aside from power boards they are in good shape and
I have a lifetime supply of ink. So with my aversion to waste,
scrapping
them is difficult.
Click to expand...
Ok. You're ecologically correct in using up your ink supply. However,
when I have the same problem, I just donate the printer and ink to a
worthy recipient. I just hate dealing with clogged nozzles and
sloooooooow printing. Laser printers are so much better.

Incidentally, I'm in the process of fixing a Behringer PMH518M
portable mixer/amp with a similar problem. The PCB is a mess. The
clever owner was running at least four 8 ohm speakers in parallel on
the output. That caused considerably more current to flow in the FET
output devices. The increased current also increased the ripple
current through the 4700uf 50V power supply caps, which got hot and
spewed electrolyte all over the PCB. When the electrolyte was finally
gone, the FET's finally decided to short out. That caused a dramatic
increase in current, which burned and eventually fused open several
traces on the PCB. It also cooked a few power resistors. The fuse
never blew. So, I have a burned PCB, with blackened electrolyte goo
all over everything, and a mess of parts to replace. The mixer is
probably only worth about $100, so I don't know why I bother. Photos
when I remember which camera has them.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 6/17/2012 1:04 AM, Jeff Liebermann wrote:
Ok. You're ecologically correct in using up your ink supply.
However, when I have the same problem, I just donate the printer
and ink to a worthy recipient. I just hate dealing with clogged
nozzles and sloooow printing. Laser printers are so much better.
Click to expand...

What model is that HP printer? I will be scrapping at least 50 of
them before long and might find a good board.
 
On Sat, 16 Jun 2012 22:04:53 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

Photos
when I remember which camera has them.
Click to expand...
This is after I cleaned off the leaky capacitor goo and removed the
fried PCB traces:
<http://www.11junk.com/jeffl/pics/repair/slides/Behringer-PMH518M-PS.html>
The replacement parts haven't arrived yet.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Jun 17, 2:08 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
    What model is that HP printer?  I will be scrapping at least 50 of
them before long and might find a good board.
Click to expand...
From memory, the oldest is a DeskJet 500 but will try to remember to
get
the numbers this weekend. Thanks, ... Peter E.
 
On Jun 17, 2:08 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:
 What model is that HP printer?  I will be scrapping at least 50 of
them before long and might find a good board.
Click to expand...
Three of them.
DeskJet 500
DeskWriter
DeskJet 560C (color)

The three external power adapters are interchangeable. The internal
power boards of the DeskJet 500 and the DeskWriter also appear to be
interchangeable. I haven't removed the internal board from the
560C.

If you have a board or two to spare, I'm happy to buy it or them.

Thanks, ... Peter E.
 
One other detail I'm curious about. The manual mentions "Power-supply PCA", "Head-driver PCA" and "Firmware on the logic PCA". PCA is printed circuit assembly? Something more arcane?

Thanks, ... Peter E.
 
On Thu, 2 Aug 2012 11:05:16 -0700 (PDT), Peter Easthope
<peasthope@shaw.ca> wrote:

One other detail I'm curious about. The manual mentions "Power-supply PCA", "Head-driver PCA" and "Firmware on the logic PCA". PCA is printed circuit assembly? Something more arcane?
Click to expand...
Nothing more arcane. That's just HP-speak. Technically "PCB" is just
a board. When populated it is an assembly, so HP are just being
pedantic to the point of being anal.
 
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