Re: 2465B Input filter


tom jobe <tomjobe@...>
 

Hi Ben,
I'm not sure, but I think that AC input filter might be a standard item from
a big parts places like Digikey, Mouser and the like.
The one you need for your 2465B has spade terminals on the back of it.
It seems like I have seen that style of input filter in the surplus stores.
A look through my Tek parts box found a very similar one from a 2235, but it
has solder lugs on the back of it. Another one from a 2246A would fit your
scope, but the spade terminals are vertical. Your spade terminals are
horizontal (if they are like this 2465 I have apart). It seems to me that
all of the 24x5's that I have seen are the same in this input filter
arrangement
The way those short wires from the input filter connect to the 2465B power
supply are, you would need a replacement filter that was very similar to
make it a simple replacement.
tom jobe...
PS Someone else mentioned having the same problem with their 2235, but they
may have been talking about the small circuit board that mounts vertically
on the back wall of the chassis. This board is part of the input filtering
on many 22xx's such as the 2235.

----- Original Message -----
From: "Ben Clarke" <benclarke@blueyonder.co.uk>
To: <tekscopes@yahoogroups.com>
Sent: Sunday, May 01, 2011 9:35 AM
Subject: [TekScopes] 2465B Input filter


My 2465B was sitting on the bench, humming to itself happily, when I
heard a soft 'phhhttt' sound, followed 5 seconds or so later by a
second one. It sounded like caps letting go but I had several items
switched on and the scope continued to run happily so it wasn't the
first suspect.

However, as I was trying to localise where the sound came from there
appeared the Awful Smell (tm), and this was obviously coming from the
scope.

After removing every cover on the scope and pulling the power supply
I still could not see any problems, but I could sure smell one!
Eventually even though the mains input filter looked fine from above,
I removed it and, sure enough, it was dripping smelly brown sludge
from underneath.

On careful inspection it was obvious that the filter had been leaking
for some time, there was a dried caked residue all round the mounting
flange which certainly could not have got there in the short time
since the Awful Smell.

So, the point of this post is, when you next have your Tek scope open
(I don't suppose this is unique to the 2465B, the same, or similar,
filters are used on many Tek scopes), have a careful look at the
input filter. I was lucky and the scope suffered no damage but the
caps in that filter are across 230v, or 120v, so a fire on failure is
not beyond the bounds of possibility, especially as it is not
protected by the unit's fuse.

Ben

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