Identify this components please.

J

Joe McElvenney

Guest
Hi,

Strapped directly across the b-e junction of a TIPL755A bipolar in a
SMPS out of a HP54502A scope is the following -

Body - cylindrical, black plastic, 5/8" long by 1/4" dia.

Body markings - MCS MTS 90A.

Leads - two, axial.

PCB marking - S1.

Polarity markings - nil.

Condition - s/c.

Naturally I don't have a schematic but my guess is that it's some sort
of over-voltage clamp. A great deal of googling hasn't helped me so
any info would be much appreciated.


Happy Holidays - Joe
 
Joe McElvenney <ximac@btinternet.com> wrote in message
news:bp5vk4db7aplhuh0th6i8maupad0hcqmt2@4ax.com...
Hi,

Strapped directly across the b-e junction of a TIPL755A bipolar in a
SMPS out of a HP54502A scope is the following -

Body - cylindrical, black plastic, 5/8" long by 1/4" dia.

Body markings - MCS MTS 90A.

Leads - two, axial.

PCB marking - S1.

Polarity markings - nil.

Condition - s/c.

Naturally I don't have a schematic but my guess is that it's some sort
of over-voltage clamp. A great deal of googling hasn't helped me so
any info would be much appreciated.


Happy Holidays - Joe
Click to expand...

inductor ?
 
Joe McElvenney wrote:
Hi,

Strapped directly across the b-e junction of a TIPL755A bipolar in a
SMPS out of a HP54502A scope is the following -

Body - cylindrical, black plastic, 5/8" long by 1/4" dia.

Body markings - MCS MTS 90A.

Leads - two, axial.

PCB marking - S1.

Polarity markings - nil.

Condition - s/c.

Naturally I don't have a schematic but my guess is that it's some sort
of over-voltage clamp. A great deal of googling hasn't helped me so
any info would be much appreciated.

Happy Holidays - Joe
Click to expand...

It doesn't appear to have the schematic but the 'service' manual is
available for free at the manufacturer's website:
<http://www.home.agilent.com/agilent/techSupport.jspx?pid=54502A%3Aepsg%3Apro&pageMode=MN&cc=US&lc=eng>


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On Mon, 22 Dec 2008 13:35:11 +0000, Joe McElvenney
<ximac@btinternet.com> put finger to keyboard and composed:

Hi,

Strapped directly across the b-e junction of a TIPL755A bipolar in a
SMPS out of a HP54502A scope is the following -

Body - cylindrical, black plastic, 5/8" long by 1/4" dia.

Body markings - MCS MTS 90A.

Leads - two, axial.

PCB marking - S1.

Polarity markings - nil.

Condition - s/c.

Naturally I don't have a schematic but my guess is that it's some sort
of over-voltage clamp. A great deal of googling hasn't helped me so
any info would be much appreciated.


Happy Holidays - Joe
Click to expand...
Is there an S2?

I don't know what a coil would be doing across a B-E junction, but can
you measure any inductance?

I can't imagine that S1 is an OV clamp, unless it is a reverse biased
diode for protection against excessive negative voltages. But then a
diode would have a polarity marking.

Does the body of the device have sharp ends (like a 1N4007 diode) or
are the ends rounded like a resistor?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
Hi everybody,

It appears that the components is a thermal switch that shunts base
current away from the switching transistor when the ambient board
temperature reaches a certain figure due to a fault condition such as
an overload or a fan failure.

I have the HP service manual but it doesn't have a parts list or
schematic for the SMPS, so I'm reduced to guessing my way round the
circuit. The unit works without the temperature switch but I can use a
locally available substitute while looking for the real thing. I am
currently investigating a source of C122F1 SCR's so I may fix the
+5.2V regulator.

BTW, I gave the marking incorrectly - twice; they are MCI MTS 90A.


Thanks for your help - Joe
 
On Wed, 24 Dec 2008 19:58:37 +0000, Joe McElvenney
<ximac@btinternet.com> put finger to keyboard and composed:

Hi everybody,

It appears that the components is a thermal switch that shunts base
current away from the switching transistor when the ambient board
temperature reaches a certain figure due to a fault condition such as
an overload or a fan failure.

I have the HP service manual but it doesn't have a parts list or
schematic for the SMPS, so I'm reduced to guessing my way round the
circuit. The unit works without the temperature switch but I can use a
locally available substitute while looking for the real thing. I am
currently investigating a source of C122F1 SCR's so I may fix the
+5.2V regulator.

BTW, I gave the marking incorrectly - twice; they are MCI MTS 90A.


Thanks for your help - Joe
Click to expand...
US patent number 5,512,732 ...

http://www.google.com/patents/pdf/Switch_controlled__zone_type_heating_cab.pdf?id=Q6ggAAAAEBAJ&output=pdf&sig=ACfU3U0QPcRUUXQKXhlZnU0Kxc1wO6MuFw

.... refers to a "ferrite reed switch" obtained from Therm-O-Disc, Inc
of Mansfield, Ohio, model MTS-90B with a Curie temperature of 90 degC.

US patent number 4,509,029 ...

http://www.google.com/patents/pdf/Thermally_actuated_switch.pdf?id=OB4vAAAAEBAJ&output=pdf&sig=ACfU3U3P7rf3GSLSDDbtsZS7rwyBfNBD3Q

.... assigned to Midwest Components, Inc, (MCI?) describes a thermal
switch consisting of "a reed switch surrounded by an annular collar
made of ferrite material and a pair of annular permanent magnets".

The latter patent refers to a brochure entitled "Thermal Reed
Switches" by Tohoku Metal Industries.

I suspect that "MTS" may stand for "Magnetic Temperature Switch".
There are plenty of Google hits for this term.

AFAICT, Midwest Components, Inc is a division of Therm-O-Disc, Inc:
http://www.thermodisc.com/index.asp

This site lists an MTS90B part made by MCI:
http://www.mwcomponents.com/~midwest/cgi-bin/partsearch.cgi?user_part=mts90

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
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