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2465 Ch1 attenuator repair question

 

Hi, On my 2465, the Ch1 BNC is slightly "loose", and the signal is intermittent depending on which way the probe cable/connector tugs on it.
The connector seems to be integral to the A10 attenuator assembly.
Looking at the maint manual, I see and understand (I think) the instructions for removing the Attenuator. But I don't see any details on how the A10 is assembled physically.
SO, my question is: If I go to the trouble to remove A10, is it likely that I can make a repair to tighten up the connector and fix the intermittent connection? Or am I going to need a replacement module?
If appropriate, does anyone have an Attenuator that you can take a picture of (with the cover removed)?

Thanks!
Pete
Chuck Harris
 

The BNC is held in place by a set screw. It is easy to
fix. The biggest problem is taking it out, as you have to
remove the knobs from below the CRT, the bezel with all of
its screws, and unsolder a couple of parts from the hybrid.

Unfortunately, the set screw is on the side away from the
bottom of the scope, so removal is necessary.

If the connector is intermittent, it is possible that a wire
or solder joint has been broken from the motion.

-Chuck Harris

saipan59 (Pete) wrote:

Hi, On my 2465, the Ch1 BNC is slightly "loose", and the signal is intermittent depending on which way the probe cable/connector tugs on it.
The connector seems to be integral to the A10 attenuator assembly.
Looking at the maint manual, I see and understand (I think) the instructions for removing the Attenuator. But I don't see any details on how the A10 is assembled physically.
SO, my question is: If I go to the trouble to remove A10, is it likely that I can make a repair to tighten up the connector and fix the intermittent connection? Or am I going to need a replacement module?
If appropriate, does anyone have an Attenuator that you can take a picture of (with the cover removed)?

Thanks!
Pete
 

One recommendation is not to pull the knobs below CRT during bezel removal (ignore step 5 in A5 removal). Over time plastic becomes brittle and every knob I tried cracked. It turns out the knobs slide off with the bezel just fine. I can send you pictures if this is not clear.
Ozan
 

I've been told that you can remove those push-on knobs by gently heating them (e.g. with a hair dryer) before you try to remove them. The heat supposedly softens the plastic enough that it will bend but not break during removal.

I broke the internal retaining clips on one of those knobs on my 2236 trying to remove it, and have been working up the courage to try the hair dryer removal method on a parts mule.

I haven't tried this yet, so take this as hearsay rather than sage advice.

-- Jeff Dutky
 

I added a photo album "2467B Bezel removal" that shows how bezel can be removed without pulling the knobs. It is not necessary and most likely knobs will be damaged (or danger of heat damaging the bezel).

/g/TekScopes/album?id=259435
---
Ozan
Chuck Harris
 

If you don't pull the knobs, you don't remove the bezel.

I don't think there is enough flex in the bezel to allow
it to bend out of the way of the CH1 and CH2 modules..
But even if there is, it would probably be a sketchy affair.

If you want to remove the knobs without breaking them, use
a pair of needle nosed pliers... whose tips are no bigger
in diameter than 1/32". Position those tips underneath the
knob skirt along a diametrical line parallel with the bezel
edge. Using the bezel edge as the fulcrum, gently pry the
knob off.

I have never broken a knob that way.

-Chuck Harris

Ozan wrote:

One recommendation is not to pull the knobs below CRT during bezel removal (ignore step 5 in A5 removal). Over time plastic becomes brittle and every knob I tried cracked. It turns out the knobs slide off with the bezel just fine. I can send you pictures if this is not clear.
Ozan
Chuck Harris
 

Ok, that makes me feel silly...

I have removed the thimble from those pots a hundred times,
and it never occurred to me that I could use that characteristic
to my advantage.

Live and learn.

Thanks Ozan!

-Chuck Harris

Ozan wrote:

I added a photo album "2467B Bezel removal" that shows how bezel can be removed without pulling the knobs. It is not necessary and most likely knobs will be damaged (or danger of heat damaging the bezel).

/g/TekScopes/album?id=259435
---
Ozan
 

Thanks for the comments so far!
As for knobs: I already played with them, and they all came off easily. One has a piece missing from the plastic 'flange' down inside the knob, but it still stays in place on the shaft. There are no metal clips or parts associated with the knobs - they are just a simple press-fit on the specially-shaped shafts.

I will go ahead and attempt the attenuator removal and repair, then report back.

Pete
 

Success!
The solder joint on the inside end of the BNC was broken. Someone had done a repair before - plastic was melted nearby from their soldering iron. There had been nothing but a bridge of solder between the cup on the BNC pin, and the post that it should attach to.
I don't know what the original connection should look like, but I made a stronger joint by wrapping a piece of wire-wrap wire around the joint, then solder-blobbed the whole thing.
The "looseness" is gone, now that the joint is attached. I couldn't see anything wrong with the BNC, and the set-screw was tight. If I treat it gently, it should be fine now.

Pete
 

Congratulations for the fix. If you haven't done already it is a good idea to check:
1) If you have surface mount CPU card SMD electrolytic caps start leaking and damaging the board (that was the case on my unit). It is best to replace them before they cause damage.
2) RIFA capacitors in power supply crack and create hazard (that was the case on my unit).

I don't know how common but NTC resistors RT1010 and RT1018 drifted quite a bit on my unit and most importantly R1010 was open circuit. There were no obvious burn marks, after close inspection there was a tiny burn hole under the resistor.

There are other things but mostly on nice to have list.

Ozan

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