Need part for Tektronix 491 Spectrum Analyzer

[Dave Woolf]

I am looking for a part for a Tektronix
491 spectrum analyzer. It is called the
RFI filter or the Low Pass 275 V AC Filter
The Tek part number as listed in my
service manual is 119-0095-00. It is a
metal can that on one end has the male
connector that the AC cord plugs into.
The other end feeds out the line voltage
to the internal fuses.

The failure is interesting. At some AC
voltage around 105 - 110 volts there is
a breakdown and short that blows a 20 amp
circuit breaker. The short is not permanent
as I can turn the unit off/on and it will again
work below the above voltage. I know it is
the filter as this is the only thing that is
before the internal fuse which never blows.

I have a work-around by running the unit
on a variac and keeping the voltage at
around 100 volts. But I am not sure how
long this will work, so I would like to
replace the filter.

Anyone know of a source?

Please remove NOSPAM from my e-mail address
if replying directly to me.

Thanks,
Dave Woolf - K8RSP

 

[Paul_Morphy]

I am looking for a part for a Tektronix
491 spectrum analyzer. It is called the
RFI filter or the Low Pass 275 V AC Filter

Well, with some care, you could make one. It's a lp filter that cuts off
somewhere above 60 Hz. If you don't want to build one, try to find some
discarded hospital electrical equipment. They all have filters that are
tested for low leakage to the chassis.

73,

"PM"

 

[zindazenda]

well in the uk these are easy to find..RS FARNELL etc all stock them..they
must be available in the states...

check on the net..g0zen

 

[Tweetldee]

I am looking for a part for a Tektronix
491 spectrum analyzer. It is called the
RFI filter or the Low Pass 275 V AC Filter
The Tek part number as listed in my
service manual is 119-0095-00. It is a
metal can that on one end has the male
connector that the AC cord plugs into.
The other end feeds out the line voltage
to the internal fuses.

The failure is interesting. At some AC
voltage around 105 - 110 volts there is
a breakdown and short that blows a 20 amp
circuit breaker. The short is not permanent
as I can turn the unit off/on and it will again
work below the above voltage. I know it is
the filter as this is the only thing that is
before the internal fuse which never blows.

I have a work-around by running the unit
on a variac and keeping the voltage at
around 100 volts. But I am not sure how
long this will work, so I would like to
replace the filter.

Anyone know of a source?

Please remove NOSPAM from my e-mail address
if replying directly to me.

Thanks,
Dave Woolf - K8RSP

http://www.sphere.bc.ca/test/tekparts.html
http://www.mpja.com/productview.asp?product=11184+FH
http://www.allelectronics.com/cgi-bin/category.cgi?category=485&type=store
http://www.alltronics.com/passive.htm

Google search for "power input module", "emi filter", or "line filter"

 

[Scott Dorsey]

I am looking for a part for a Tektronix
491 spectrum analyzer. It is called the
RFI filter or the Low Pass 275 V AC Filter
The Tek part number as listed in my
service manual is 119-0095-00. It is a
metal can that on one end has the male
connector that the AC cord plugs into.
The other end feeds out the line voltage
to the internal fuses.

You can replace it with a stock Corcom EMI filter from Digi-Key.

The failure is interesting. At some AC
voltage around 105 - 110 volts there is
a breakdown and short that blows a 20 amp
circuit breaker. The short is not permanent
as I can turn the unit off/on and it will again
work below the above voltage. I know it is
the filter as this is the only thing that is
before the internal fuse which never blows.

This thing is a pi filter with an inductor inside and some shunt
capacitors. One of the capacitors is on the way out.

I have a work-around by running the unit
on a variac and keeping the voltage at
around 100 volts. But I am not sure how
long this will work, so I would like to
replace the filter.

Anyone know of a source?

Open it with a can opener and replace the ceramic caps.
--scott