Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Identify this components please.

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
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Joe McElvenney wrote in message
...
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



inductor ?




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Default Identify this components please.


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



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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Default Identify this components please.

On Mon, 22 Dec 2008 13:35:11 +0000, Joe McElvenney
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


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
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Default Identify this components please.

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


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Default Identify this components please.

On Wed, 24 Dec 2008 19:58:37 +0000, Joe McElvenney
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


US patent number 5,512,732 ...

http://www.google.com/patents/pdf/Sw...0K xc1wO6MuFw

.... 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/Th...sZS7rwyBfNBD3Q

.... 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...ser_part=mts90

- Franc Zabkar
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