On 2022-09-06, at 18:27, Keith <keith@...> wrote:

I haven't replaced the schaffner filter on my two 3458A's. Keysight don't change them automatically if they repair a unit, so I guess they are not expecting them to fail suddenly.

I don’t know off-hand how similar the 3457A ones are, but these do fail, and need to be replaced on sight.

(And I do hate those rivets — drilling them out is not what I want to do, given the danger of metal shavings making it into the instrument.)

Grü?e, Carsten

I haven't replaced the schaffner filter on my two 3458A's. Keysight don't change them automatically if they repair a unit, so I guess they? are not expecting them to fail suddenly.

If you do replace the shaffner, also consider C15/16 on the outguard power supply board which are 2200pF 250VAC rated - and on mine look like rifa's.

OK, maybe I'm getting it, internally the the 10db attenuator section maybe stuck in circuit.
?I have no idea of the construction, so didn't know that was possible.
?????????????????????????????????? Thanks, Mikek

Not exactly sure what you mean, but I have verified that every attenuator setting is 10db low.
Using my scope and using another generator.

Yeah, I've had them go bang on other instruments and it makes a mess. You might want to do it at the same time as the electrolytics and also socket and renew the battery-backed sram if it's not already. Here's my parts list:



The key thing to avoid an unnecessary recal, of course, is to extract the calram contents promptly. There are loads of utilities around to do that over gpib.

There's lots of discussion on this and related subjects on the eevblog metrology forum.

Alan

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I did find a note in the files section that there could be a pin the has slide out of it's hole enough that it can stop the knob from turning to that last -140db position.
I'm still 10db low!
????????????? Thanks, Mikek

?I've been checking a meter and thought something was wrong with the meter as it read 10db low. I was stepping 10db each time and it was accurate but 10db low.
Then I switched generators and then the meter was right. I measured the loaded voltage of my 8640B and yes, the output is 10db low.

?What could cause this unit to have an output exactly 10db low?

I do notice the the output step attenuator knob stops at +20db and at -130db, but will not switch to -140db as the dial indicates.
?
???????????????????????????? Thanks, Mikek

On Tue, Sep 6, 2022 at 2:14 PM Chuck Harris <cfharris@...> wrote:

If you are in the USA, you will probably never witness
a Schaffner filter fail. If you are in 220-240V land, you
may not be so lucky.

When the filters fail, the worst that happens is they release
a little foul smoke, and sometimes a little tar. Both problems
are pretty easy to clean up... if they happen.

Being in the US, my policy is to leave them alone, and to
fix any that fail, when they fail. If I were in 220-240V land,

I definitely live in 240V land (even more when the PV plant is active).
Many schaffner filters died or were found dead when I acquired various
test gears.
However, I've not replaced them "on sight", I still have a few
instruments (Solartron, Data I/O)
with the original filters and I don't plan to mess with them unless
they release the magic and stinky
smoke first.

Frank IZ8DWF

If you are in the USA, you will probably never witness
a Schaffner filter fail. If you are in 220-240V land, you
may not be so lucky.

When the filters fail, the worst that happens is they release
a little foul smoke, and sometimes a little tar. Both problems
are pretty easy to clean up... if they happen.

Being in the US, my policy is to leave them alone, and to
fix any that fail, when they fail. If I were in 220-240V land,
I would replace them on sight. The rivets are a simple problem.
Center punch them, drill them out, and use a fresh pop rivet
when you replace the filter.

-Chuck Harris


On Tue, 06 Sep 2022 01:30:40 -0700 "Stephen Bell"
<s.r.bell@...> wrote:

I have recently acquired a 3458A which incorporates a Schaffner
FN9223-3-06 mains filter. The 3458A has a build date of approx 2005
and the Schaffner filter has a date code of 0432.

I am wondering if these later Schaffner filters have the same
dramatic failure mode exhibited by their earlier models and whether
it should be replaced. I am reluctant to replace it if it is not
necessary due to it being riveted into the chassis.

Hi Dan,
Assuming you download the User Guide from
Then we have the same page numbers.
On page 149 you can see how to place the analyzer on its side and continue reading on page 171 how to foldout the A2 and A3 boards.
In short you have to remove all the screws (several lengths) from the top board A2. Disconnect the two flatcable connectors at the back of the board for easier foldout. One is for the HPIB connector and the other is for the 85620A Mass Memory Module connector, both on the rear of the instrument.
Then you can foldout the A2 board and the A3 board will come along.? They have to come both.
Then you have access to the A17 board close to the rear end of the CRT unit.
Use a long plastic trimmer stick. Its's high voltage in there. Then proceed with page 64 from my previous message.
Be careful and good luck.

jaap

On 2022-09-06, at 10:58, Adrian Nicol <Adrian@...> wrote:

Any 'stand alone' yellow Rifa caps you find serving as input filters should be changed with extreme prejudice on sight however!

Yes. The point about Schaffner filters is that X caps of this type (reportedly from WIMA, not RIFA) were use in their line filters up to some point, which (together with the fact that they make a somewhat sealed enclosure) is the reason they explode.

The question really is when Schaffner stopped using the “clear epoxy blob” type of X cap and switched to caps that didn’t have that fatal flaw.

Your data seems to suggest mid-1990s or earlier.

Can we get more precise?
Maybe obtain a statement from the horse’s mouth?
(Somebody in this mailing list must have worked for Schaffner…)

Grü?e, Carsten

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As far as I know there is not a problem. We've fitted hundreds of assorted types of Schaffner IEC input filters to equipment since the mid 1990s and as far as I know without any failure. I suppose there may have been failures but our customers may just not have mentioned it to us? (Unlikely!)

It is true that most of those will have been living in 220/240VAC land their whole lives whereas the only HP fitted one I've had fail went within a day or so of crossing the Atlantic and seeing 240V for the first time.

Any 'stand alone' yellow Rifa caps you find serving as input filters should be changed with extreme prejudice on sight however!?

I have recently acquired a 3458A which incorporates a Schaffner FN9223-3-06 mains filter. The 3458A has a build date of approx 2005 and the Schaffner filter has a date code of 0432.

I am wondering if these later Schaffner filters have the same dramatic failure mode exhibited by their earlier models and whether it should be replaced. I am reluctant to replace it if it is not necessary due to it being riveted into the chassis.

I am still trying to find the time to get back to it but it may end up becomming more of a winter project looking at the bench at the moment. I understand that there may be many more hidden issues to work through but I will chip away at it as time allows and update as I go along. Thank you to all for the input so far. Karl

Jaap - thank you that's a great find!
Now ....? how did you get to that control? I have the cover off and can't see how to get to that board!
Thanks
Dan

I checked the shotky diodes in first mixer and they beep in both directions with the meter in diode check. .262 volts. Not a continuous beep but a short one. Also it spears both ends of the diode are tied together,? I read continuity.? Is that correct ?

Perhaps someone dialed in an offset? Press the green preset button to put the instrument back to its normal state and see if that fixes the issue.

I'm having a issue with a fail code 1310 . Of the 16 leds number 4 and number 12 are lit, but this problem go's away sometimes.? I think the revision is 11,12,86.the service manual is kinda confusion.is this something I can correct entering info or something . Thanks.?

On 9/5/22 10:59, Yue wrote:

Did you check the battery for memory backup ? not sure the 70000 has battery or not but the module should easy to remove for inspection

The 70900A/B Local Oscillator module contains a Tadiran TL5104/P battery. It maintains the SRAM contents, including basic configuration info and any stored DLPs. I don't know what's causing the problem with Dave Miller's LO module, but I'm pretty sure it's not the battery.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA