Hi all,

I have a dead HDD I am trying to fix for a friend. I have a
replacement PCB to see if that sorts it but it involves
desoldering the ROM chip from the original board and soldering it
on to the new board.

When I was taking the ROM chip off the new board I inadvertently
took off a nearby component.

I have uploaded a couple of pictures here
https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D--

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

I have been in discussion with the PCB supplier who specialises in
these boards as well as fixing them. He said that this component
is not critical and I should try the PCB without it.


Couple of questions
1. Any idea what the component is? A resistor?
2. On the new board you can see that the pads the component sits
on are now not connected as it would be through the missing
component. If the component is not critical, my guess would have
been that I at least need to connect the pads together?
3. Another option is to take the one off the original board and
use that. Is that viable with a regular soldering iron? Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

Also, any view from the experts on what best to do?

Thanks in advance

Lee.


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On 22/11/2020 19:20, Lee Nowell wrote:

https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D

The photo is of such poor resolution that it it is impossible to see the
component, the tracks to it or any of the legend in the IC to which it
is connected.

The component may be a power supply decoupling capacitor so on no
account short out the pads. If it is a capacitor then
i) it probably will not make any difference to the operation of the circuit
ii) shorting the pads may short one of the power supplies and destroy
other components on the board.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

alan_m wrote:
On 22/11/2020 19:20, Lee Nowell wrote:

https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D

The photo is of such poor resolution that it it is impossible to see the
component, the tracks to it or any of the legend in the IC to which it
is connected.

I had to delete the -- from the URL, but by the looks of it that's the
firmware flash chip for the processor which has the thermal pad on it (which
obscures its part number).

Assuming the flash is the standard SPI NOR flash pinout, that would be
pin 7 which is HOLD# - see eg:
https://www.winbond.com/resource-fil...2003112019.pdf

The other end disappears in a via so hard to know where it goes, but that
file suggests a 10K pullup resistor, which would fit your board if the
the resistor's via goes to VCC (usually an inner board plane so no tracks
visible on the other side).

Theo

On Sun, 22 Nov 2020 19:20:51 +0000 (GMT), Lee Nowell
wrote:

snip

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

As has been mentioned I don't think there is sufficient detail to be
sure but if it's only two legs it should only be a cap, resistor or
diode. ;-)

snip

If the component is not critical, my guess would have
been that I at least need to connect the pads together?

Probably definitely not. ;-)

3. Another option is to take the one off the original board and
use that.

Why don't you (try to) measure the value of the one you still have. If
you are lucky it will be a resistor and read a preferred value, like
1k, 4.7k etc? If you have a DMM, do it on the std resistance range,
not the diode test. If you measure both ways round, get the same
reading of a sensible value, the chances are it was a resistor. If you
just get a pulse as you go either way round, it's more likely a cap
and if the values differ each way, it might be a diode (but could also
be the circuitry around it).

You sometimes have to be careful measuring stuff in circuit, less you
damage anything (sensitive circuitry) around it.

Is that viable with a regular soldering iron?

One with a reasonable fine tip yes. If your eyes are good enough, you
can sometimes put some flux on the area and (quickly) flood the
component with solder (so it bridges it) and then you can (quickly)
lift it off with some fine tweezers.

Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

Yeah, not generally an issue re which way round if it's a resistor but
might be if it's a cap and deffo a diode. ;-)


Also, any view from the experts on what best to do?

We will have to wait and see. ;-)

Cheers, T i m

On Sun, 22 Nov 2020 19:20:51 +0000 (GMT), Lee Nowell
wrote:


Hi all,

I have a dead HDD I am trying to fix for a friend. I have a
replacement PCB to see if that sorts it but it involves
desoldering the ROM chip from the original board and soldering it
on to the new board.

When I was taking the ROM chip off the new board I inadvertently
took off a nearby component.

I have uploaded a couple of pictures here
https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D--

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

I have been in discussion with the PCB supplier who specialises in
these boards as well as fixing them. He said that this component
is not critical and I should try the PCB without it.


Couple of questions
1. Any idea what the component is? A resistor?
2. On the new board you can see that the pads the component sits
on are now not connected as it would be through the missing
component. If the component is not critical, my guess would have
been that I at least need to connect the pads together?
3. Another option is to take the one off the original board and
use that. Is that viable with a regular soldering iron? Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

Also, any view from the experts on what best to do?

Thanks in advance

Lee.


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Usually on such boards resistors have values marked but caps don't.
Your component is certainly not a link as there is no track underneath
that requires a link to bridge it. It looks like the same kind of cap
as is across the narrow pair of tracks under your arrow that go into
the corner of the square IC. Probably you could use that to replace
the missing one.
--
Dave W

Dave W wrote:

Your component is certainly not a link as there is no track underneath
that requires a link to bridge it.

It's not unusual for zero ohm resistors to be used as links, but the
photo isn't good enough to make out any markings, a camera with a macro
lens and some strong lighting might help ...

Andy Burns wrote:
Dave W wrote:

Your component is certainly not a link as there is no track underneath
that requires a link to bridge it.

It's not unusual for zero ohm resistors to be used as links, but the
photo isn't good enough to make out any markings, a camera with a macro
lens and some strong lighting might help ...

I've always found "zero ohm resistors" a rather wierd concept, surely
that's either a link or just a piece of wire. Why call it a
'resistor' when it's not?

--
Chris Green
·

Chris Green wrote:
Andy Burns wrote:
Dave W wrote:

Your component is certainly not a link as there is no track underneath
that requires a link to bridge it.
It's not unusual for zero ohm resistors to be used as links, but the
photo isn't good enough to make out any markings, a camera with a macro
lens and some strong lighting might help ...

I've always found "zero ohm resistors" a rather wierd concept, surely
that's either a link or just a piece of wire. Why call it a
'resistor' when it's not?


It's a surface-mountable wire, which fits into the whole
manufacturing process. It can be placed at high speed,
and doesn't slow down the pick-and-place when used.
The SMT item can be affixed with a glue dot like
any other resistor, and won't fall off going through
the line. What's not to like ? You put a reel of 3500 of
those on the machine, press the button and off it goes.

Generally you try to use those, in places where it
won't affect circuit performance. It can be used on a
Bill Of Materials (BOM) to control the addition or
subtraction of optional circuit blocks.

And just because it's zero ohms, you don't go around
running 20 amperes through it on purpose :-/ Although
some of my colleagues have probably thought about
doing that. Because they are zero ohms and its magical.
They're like tiny superconductors, right ? I can think
of at least one engineer who would fall for that. And
no, I've never ohmed one out to see what its real
resistance is. I'm sure there's an estimate around
somewhere.

As another example of a function, I could put a zero ohm
today, and if I get in the lab and discover a logic signal
needs series damping with a 33 ohm, change the BOM to read
33 ohms, and then when manufacturing starts, I look like
a genius. You'll find all sorts of lands on PCBs that
are optional, and are a form of "hedging" against unexpected
surprises. You'll find people putting extra lands on
boards, even without thinking about it (like, they've copied
a chunk of design from some place else, complete with
options they don't understand).

You can even do zero ohms like this, but manufacturing is
going to be phoning you if they spot stuff like this. The
rules set for PCB design, is several feet thick. I'm sure
that breaks some rule or rules. You can do stuff like
this if the land is square, and rotating a component is
footprint compatible.

R1
--------X X--------- destination #1
R2
X
|
|
destination #2

If in the BOM, I set R2 to zero ohms, then my signal is going
off to destination #2. And then I depop R1 so that leg is open
circuit. Voila, circuit change after schematic capture is finished.
I can put R1 or R2 in the BOM, but not both.

The opportunities for abuse are endless. Especially if the
engineer doesn't document what all that crap is for.

On things like computer motherboards, you'd remove stuff like
that for the third and final design cycle, before high volume
manufacturing starts. Because a zero ohm resistor costs money
and "it has to go". But on "material cost is no object" circuit
boards, where you're only making 300 boards a year, you'll see
stuff like that. Like, I make a logic board with $10K worth
of logic chips, and I charge the customer $100K for it. The
cost of a zero ohm really doesn't matter then.

Paul

On 22/11/2020 19:20:51, Lee Nowell wrote:
Hi all,

I have a dead HDD I am trying to fix for a friend. I have a
replacement PCB to see if that sorts it but it involves
desoldering the ROM chip from the original board and soldering it
on to the new board.

When I was taking the ROM chip off the new board I inadvertently
took off a nearby component.

I have uploaded a couple of pictures here
https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D--

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

I have been in discussion with the PCB supplier who specialises in
these boards as well as fixing them. He said that this component
is not critical and I should try the PCB without it.


Couple of questions
1. Any idea what the component is? A resistor?
2. On the new board you can see that the pads the component sits
on are now not connected as it would be through the missing
component. If the component is not critical, my guess would have
been that I at least need to connect the pads together?
3. Another option is to take the one off the original board and
use that. Is that viable with a regular soldering iron? Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

The pinout seems consistent with a SPI Serial Flash memory where pin 3
is a nWP or write protect pin.

There might be a internal block protection bits that is used in
conjuction with this pin.

If the device is pre-programmed then the level shouldn't matter,
otherwise the pin has to be held high and I would expect the resistor is
passively holding the pin low to prevent inadvertent programming.

Without more details of the device the above is an educated guess.

Lee Nowell wrote:
Hi all,

I have a dead HDD I am trying to fix for a friend. I have a
replacement PCB to see if that sorts it but it involves
desoldering the ROM chip from the original board and soldering it
on to the new board.

When I was taking the ROM chip off the new board I inadvertently
took off a nearby component.

I have uploaded a couple of pictures here
https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D--

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

I have been in discussion with the PCB supplier who specialises in
these boards as well as fixing them. He said that this component
is not critical and I should try the PCB without it.


Couple of questions
1. Any idea what the component is? A resistor?
2. On the new board you can see that the pads the component sits
on are now not connected as it would be through the missing
component. If the component is not critical, my guess would have
been that I at least need to connect the pads together?
3. Another option is to take the one off the original board and
use that. Is that viable with a regular soldering iron? Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

Also, any view from the experts on what best to do?

Thanks in advance

Lee.

It looks to me like this. Your second
picture shows 3 is joined to 7, so /WP is
joined to /HOLD, and it's like the functions
are not being used. They would be going to a
pullup to put them in the negated (not used) state.

This is just to show the basic idea.

+-----+----- 10K ---- 3.3V
| |
3 7
/WP /HOLD
I/O I/O === outputs in quad SPI mode, so only want
vanilla SPI operation while wired this way.

I can't find an exact match for the part number on
Winbond, so this is close to it but not the precise item.

https://www.winbond.com/hq/support/r...y%2Findex.html

https://www.winbond.com/resource-fil...g_07212015.pdf

What I seem to be seeing in there, is no definition of any
built-in pullup on those pins. Which is passing strange. Normally,
chips have a weak function for pins, such that no resistors
are needed externally. It's unusual for any modern chip
to be completely devoid of a function like that. Tying the
pin to the deasserted state, would be a fairly common practice.

Typically, people seem to remove some ROM from controller
boards, and transfer it from the old board. There's some kind
of check that the controller and disk are matched somehow.
Forcing people who do controller swaps, to bring over the old chip.
Now, if the chip was dead, I don't know what they're supposed
to do with regard to recovery. Each SPI flash has a custom
(Winbond factory) written serial number, so it is possible for a check
to be done.

The code in the flash, isn't the whole code load. The service
area has code too. The code in the flash is sufficient to move the
arm over to the service area and read the rest of the code content.
It's something like that.

If you copied code from one flash chip to another, the serial
number of the second chip would still be wrong. It wasn't
always necessary to swap those chips, but it's become a "thing"
on the more modern drives.

This is information I've been able to glean from a couple data
recovery forums on the web. They don't come right out and
explain stuff, so you have to collect enough tidbits from
what they say, to spot a pattern.

Not all the controller boards are recovered from dead drives.
Some of the controller boards are available as brand new items.
But that still does not remove the need to swap SPI, if that's
what the design era calls for. The 4GB WDC I have here from the
year 2000, would not need that. A straight up controller swap would
work there. The controller board is likely around 6 years old
(just a very rough guess).

Paul

On Sun, 22 Nov 2020 23:25:55 -0500, Paul
wrote:

snip

This is information I've been able to glean from a couple data
recovery forums on the web. They don't come right out and
explain stuff, so you have to collect enough tidbits from
what they say, to spot a pattern.

snip

This is often a problem with 'technical people' in general.

1) They are often of a mindset that has led them to be in that field.

2) Because they are often immersed in that field they forget how 'most
other people' wouldn't have a clue when stuff is seen in abstract.

3) Because they are in that field and of that mindset they aren't good
at writing user manuals for others not like them. ;-)

All this was reinforced when I moved from a lifelong role in 'IT
Support' to 7 years as an IT Trainer, seeing how many people hadn't
really used a screwdriver or a mouse, let alone understood static
electricity or binary.

Where this appears at it's worst (the assumptions re baseline
understanding) is websites offering fairly technical solutions where
unless you knew what the software did, you wouldn't be able to work it
out from the site.

It tells you that V3.5 is now available and that it does XYZ better
than the old version but with no mention of what it does, unless you
knew what all the acronyms meant. DAW, OBD etc.

This is why I can rarely make any practical progress with Linux
related things.

With Windows / OSX you generally download a 'Setup' file of some sort,
run it and away you go. They might have included some installation
instructions because there are likely to be millions of users.

For Linux the chances are there will be fewer users and (and 'what
Linux' exactly) so you are often left installing / building / finding
/ installing dependencies yourself and the only chance of me being
able to do that with any hope of success is pretty low. Unless I can
find a walkthrough, written by someone similar to me who actually
covers *all* the steps in a form that someone not into the details can
use, even if they don't understand.

For many the point is the end, not the means, as really should be the
case for an ordinary user and an OS.

Cheers, T i m

No don't short it, it might be a capacitor. I hate surface mount.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Lee Nowell" wrote in message
...
Hi all,

I have a dead HDD I am trying to fix for a friend. I have a
replacement PCB to see if that sorts it but it involves
desoldering the ROM chip from the original board and soldering it
on to the new board.

When I was taking the ROM chip off the new board I inadvertently
took off a nearby component.

I have uploaded a couple of pictures here
https://drive.google.com/folderview?id=1mvAgXH2
psjYEIl7_ErrHKdEpucKCd15D--

One photo shows the new board with the original ROM soldered in
place and a red arrow showing where the missing component is. The
other photo shows the original board with the ROM removed but you
can see the component that is missing on the new one - it looks
like a black bar.

I have been in discussion with the PCB supplier who specialises in
these boards as well as fixing them. He said that this component
is not critical and I should try the PCB without it.


Couple of questions
1. Any idea what the component is? A resistor?
2. On the new board you can see that the pads the component sits
on are now not connected as it would be through the missing
component. If the component is not critical, my guess would have
been that I at least need to connect the pads together?
3. Another option is to take the one off the original board and
use that. Is that viable with a regular soldering iron? Also,
depending on what it is I guess it could have a particular
orientation which adds more complexity

Also, any view from the experts on what best to do?

Thanks in advance

Lee.


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On 23/11/2020 09:25:22, Brian Gaff (Sofa) wrote:
No don't short it, it might be a capacitor. I hate surface mount.
Brian

I'm now a fan of surface mount. Far easier to remove a component off
without taking the lands with it. Multi-pin components come off with a
hot air gun.

What I do hate is BGAs.

Hi all,

I have taken a few more photos with our camera (had to find it and charge it first as haven't used in a couple of years). They are in the same location as the others https://drive.google.com/drive/folde...5D?usp=sharing

Trying to get a photo of what is written on the chip is next to impossible. So best I can make out the following is written on the top of the 2 chips
Chip 1 -
25FS406
06
2PHON

Chip 2 -
Winbond
25040BW607
1244

In terms of the circuit board. As has been mentioned above, it looks like it goes
pin 7 - missing component - pin 3 of same chip
pin 7 - hole in circuit board but nothing the other side.

There is no writing on the missing component that I can see so I assume it is a resistor? Checking the resistance with a DMM I get 1880 in both directions.

Based on this and from what I understand from the various replies, it sounds like this is to ensure the chip doesn't go into reprogram mode and therefore safe enough for me to test the board without the component. Is this correct?

Thanks again for all your help

Lee.

On Tue, 24 Nov 2020 02:56:55 -0800 (PST), "
wrote:

snip

There is no writing on the missing component that I can see so I assume it is a resistor?

Or a cap and so you are measuring 'resistance' of whatever else
appears across those two connections. The only true way to tell would
be to disconnect that component and measure it out of circuit. Or, all
other things being equal, measure across where the component was on
the other board and see what that reads (may not be possible if you
have removed associated components).

Checking the resistance with a DMM I get 1880 in both directions.

That may confirm it's not a diode at least, and that it's not a link.
;-)


Cheers, T i m

T i m Wrote in message:r
On Tue, 24 Nov 2020 02:56:55 -0800 (PST), wrote:snipThere is no writing on the missing component that I can see so I assume it is a resistor?Or a cap and so you are measuring 'resistance' of whatever elseappears across those two connections. The only true way to tell wouldbe to disconnect that component and measure it out of circuit. Or, allother things being equal, measure across where the component was onthe other board and see what that reads (may not be possible if youhave removed associated components).Checking the resistance with a DMM I get 1880 in both directions.That may confirm it's not a diode at least, and that it's not a link.;-)Cheers, T i m

Aha yes good point. With the chip removed, those pads read 1.7M
is one direction and 2.4M is the other. Not that helps us
though?
--


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On 24/11/2020 10:56:55, wrote:
Hi all,

I have taken a few more photos with our camera (had to find it and
charge it first as haven't used in a couple of years). They are in
the same location as the others
https://drive.google.com/drive/folde...5D?usp=sharing

Trying to get a photo of what is written on the chip is next to
impossible. So best I can make out the following is written on the
top of the 2 chips Chip 1 - 25FS406 06 2PHON

Which is a Sanyo Serial Flash memory as suggested:

https://pdf1.alldatasheet.com/datash...LE25FS406.html

On Semi bought Sanyo and not sure how to access the old Sanyo parts
directly.

Chip 2 - Winbond 25040BW607 1244

Which I haven't looked up but assume it is a volatile memory.

In terms of the circuit board. As has been mentioned above, it looks
like it goes pin 7 - missing component - pin 3 of same chip pin 7
- hole in circuit board but nothing the other side.

There is no writing on the missing component that I can see so I
assume it is a resistor? Checking the resistance with a DMM I get
1880 in both directions.

Which does suggest a 1.8k resistor. Possibly a bit lower in value than I
would have used and higher tolerance. 1% resistors are the norm. It
costs more to put them on a PCB than the actual cost of the component.

Based on this and from what I understand from the various replies, it
sounds like this is to ensure the chip doesn't go into reprogram mode
and therefore safe enough for me to test the board without the
component. Is this correct?

What it does do is ensure the default level is write-protect, so that if
there is a corruption in the micro the memory won't be overwritten.

Writing to a Flash memory is non-trivial, with specific codes being sent
to enable writing, even when the nWP pin is high.

I would say it is normally safe, but would be safer with the resistor
fitted.