24 Dec
2017
24 Dec
'17
10:27 a.m.
I am continuing work to reverse engineer the schematic for my H7826 PSU. I
have removed one of the daughter cards in order to draw its schematic, but I
can't identify some of the surface mount components on it. I have posted a
picture of it here:
https://rjarratt.files.wordpress.com/2017/12/50-19530.jpg
The ones I can't identify are:
1. The component with two wide pins that looks like an IC
approximately in the middle of the board. It is marked M106 (or it might be
AA106) and 91813 underneath. I think it may be a resistor, but I am not
sure.
2. Just to the right of this is another much thinner two-pin component
which is black on top with a kind of white notch. I have no idea at all what
this is.
3. The three 3-pin black components to the left of the first
component. Two of them are marked "2T L" (or is that "ZT L"?), one
appears
to be marked "2X I" (letter "ih", not letter "el"). I guess
they are
transistors, but they may not be of course, and I don't know their pinout.
Any help with identifying what these are would be very helpful.
Thanks
Rob
24 Dec
24 Dec
10:39 a.m.
On 12/24/2017 10:27 AM, Rob Jarratt via cctalk wrote:
1. The component with two wide pins that looks like an IC
approximately in the middle of the board. It is marked M106 (or it might be
AA106) and 91813 underneath. I think it may be a resistor, but I am not
sure.
2. Just to the right of this is another much thinner two-pin component
which is black on top with a kind of white notch. I have no idea at all what
this is.
3. The three 3-pin black components to the left of the first
component. Two of them are marked "2T L" (or is that "ZT L"?), one
appears
to be marked "2X I" (letter "ih", not letter "el"). I guess
they are
transistors, but they may not be of course, and I don't know their pinout.
My guesses are as follows.
1. That "AA" or "M" looks to me like a Motorola logo. The fact that
this device is polarized leads me to suspect that it's a diode.
2. I suspect that this thing is a fuse.
3. Almost certainly transistors. The center pin is usually the collector.
--Chuck
11:15 a.m.
My guesses are as follows.
1. That "AA" or "M" looks to me like a Motorola logo. The fact that
this device
is polarized leads me to suspect that it's a diode.
2. I suspect that this thing is a fuse.
3. Almost certainly transistors. The center pin is usually the collector.
--Chuck
Many thanks, those make sense. I tested the first one in circuit to see if it was a diode
and that seems to be correct.
I think the orange components are capacitors (they are taller than the browner ones), but
their markings don't seem to hint at the values, some are marked "AA4",
which does not seem to correspond to any marking scheme I have been able to find. Any idea
if they *are* capacitors and what the values might be?
Regards
Rob
12:01 p.m.
On 12/24/2017 11:15 AM, Rob Jarratt wrote:
I think the orange components are capacitors (they are
taller than the browner ones), but their markings don't seem to hint at the values,
some are marked "AA4", which does not seem to correspond to any marking scheme I
have been able to find. Any idea if they *are* capacitors and what the values might be?
My guess is capacitors also. This "SMD Code Book" should be of some value:
http://www.sphere.bc.ca/download/smd-codebook.pdf
--Chuck
12:23 p.m.
On 2017-Dec-24, at 12:01 PM, Chuck Guzis via cctalk wrote:
On 12/24/2017 11:15 AM, Rob Jarratt wrote:
Noting they are paralleling resistors, they're probably just noise/AC bypass, on the
order of 0.01 uF, and not overly consequential to understanding the basic circuit.
Again, one can draw it out with the above presumption and then assess whether it makes
sense or for alternative functions.
I think the orange components are capacitors
(they are taller than the browner ones), but their markings don't seem to hint at the
values, some are marked "AA4", which does not seem to correspond to any marking
scheme I have been able to find. Any idea if they *are* capacitors and what the values
might be?
My guess is capacitors also. This "SMD Code Book" should be of some
value:
http://www.sphere.bc.ca/download/smd-codebook.pdf
--Chuck
1 p.m.
My guess is capacitors also.
Noting they are paralleling resistors, they're probably just noise/AC the order of 0.01 uF, and not overly consequential to
understanding the
basic
circuit.
Again, one can draw it out with the above presumption and then assess
whether it makes sense or for alternative functions.
> This "SMD Code Book" should be of some value:
>
> http://www.sphere.bc.ca/download/smd-codebook.pdf
>
I am indeed drawing it out. Whether I have drawn it logically or not I am
not sure. I will check it with reference to the main input stage of the PSU,
where this board has come from. Could the reference be associated with the
input voltage auto-sensing? Or is this overly elaborate for that purpose?
That unmarked flat part does appear to have some resistance, about 390ohms
as measured in circuit, so probably the precision trimmed resistor you
suggest.
Regards
Rob
12:04 p.m.
On 2017-Dec-24, at 10:27 AM, Rob Jarratt via cctalk wrote:
I am continuing work to reverse engineer the schematic
for my H7826 PSU. I
have removed one of the daughter cards in order to draw its schematic, but I
can't identify some of the surface mount components on it. I have posted a
picture of it here:
https://rjarratt.files.wordpress.com/2017/12/50-19530.jpg
The ones I can't identify are:
1. The component with two wide pins that looks like an IC
approximately in the middle of the board. It is marked M106 (or it might be
AA106) and 91813 underneath. I think it may be a resistor, but I am not
sure.
2. Just to the right of this is another much thinner two-pin component
which is black on top with a kind of white notch. I have no idea at all what
this is.
3. The three 3-pin black components to the left of the first
component. Two of them are marked "2T L" (or is that "ZT L"?), one
appears
to be marked "2X I" (letter "ih", not letter "el"). I guess
they are
transistors, but they may not be of course, and I don't know their pinout.
Any help with identifying what these are would be very helpful.
SMD codes are a mess as the same code is often used by different manufacturers for
different devices.
Resolving them is often an effort working between the multiple code possibilities, what
makes electrical sense after reverse engineering the circuit topology, and ohmmeter
measurements of the device.
2: Try measuring the resistance, if it's a low resistance perhaps a fuse as Chuck
suggested, but considering the precision reference on the board, if it's a higher
resistance perhaps a precision-trimmed resistor.
3: As per Chuck's suggestion likely bipolar transistors, and probably:
2T: PNP
2X: NPN
with pinout (hopefully this renders unambiguously):
C
B E
Try drawing it out presuming the above and then assess whether it makes sense electrically
for polarity, current flow and control.
2:07 p.m.
If you could wait, getting one of those ?unknown component testers? would help you!
David Collins
On 25 Dec 2017, at 5:27 am, Rob Jarratt via cctalk
<cctalk at classiccmp.org> wrote:
I am continuing work to reverse engineer the schematic for my H7826 PSU. I
have removed one of the daughter cards in order to draw its schematic, but I
can't identify some of the surface mount components on it. I have posted a
picture of it here:
https://rjarratt.files.wordpress.com/2017/12/50-19530.jpg
The ones I can't identify are:
1. The component with two wide pins that looks like an IC
approximately in the middle of the board. It is marked M106 (or it might be
AA106) and 91813 underneath. I think it may be a resistor, but I am not
sure.
2. Just to the right of this is another much thinner two-pin component
which is black on top with a kind of white notch. I have no idea at all what
this is.
3. The three 3-pin black components to the left of the first
component. Two of them are marked "2T L" (or is that "ZT L"?), one
appears
to be marked "2X I" (letter "ih", not letter "el"). I guess
they are
transistors, but they may not be of course, and I don't know their pinout.
Any help with identifying what these are would be very helpful.
Thanks
Rob
4:04 p.m.
-----Original Message-----
From: David Collins [mailto:davidkcollins2 at gmail.com]
Sent: 24 December 2017 22:07
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: Help Identifying Components
If you could wait, getting one of those ?unknown component testers? would help
you!
I have a fairly simple one actually, a Peak Atlas DCA55, but I would prefer to identify
components without desoldering. If anyone would like to recommend a good tester that
doesn't cost too much I would consider getting a better one.
Regards
Rob
2554
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