On 9/11/22 20:04, Donald Viszneki wrote:

Is the mmwave space not popular in this group?

I don't think that's fair to say at all..

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Is the mmwave space not popular in this group?

So lets poll the audience to see if we can get a rough upper and lower time boundary.
The device of mine with these RIFA caps has a serial prefix of 2839, corresponding to week 39 of 1988 (1960+28). What instrument manufacture dates before and after this one have people seen problematic RIFAs in?

On 9/11/22 19:08, Toby wrote:

Linear vs. SMPS would not be expected to matter, in any case. The problem is one of moisture ingress. The encapsulant shrinks and cracks over time, letting moisture in. At some point the capacitor breaks down and you get a multimedia spectacular. None of those processes is particularly sensitive to what circuitry lies downstream.

?? It's my understanding that it doesn't happen quite like this.? My understanding is that the epoxy is hygroscopic, and its mass increases as it absorbs moisture.? The mass of epoxy swells, causing first crazing, then full cracking of the outer shell.? Leakage increases and

Relateable. That's the path most of us are on.

tea -> keyboard

Yes, exactly!

*BLAM!*

--
Dave McGuire, AK4HZ
New Kensington, PA

On 2022-09-11 7:05 p.m., Dave McGuire wrote:

On 9/11/22 18:41, Tom Lee wrote:

Linear vs. SMPS would not be expected to matter, in any case. The problem is one of moisture ingress. The encapsulant shrinks and cracks over time, letting moisture in. At some point the capacitor breaks down and you get a multimedia spectacular. None of those processes is particularly sensitive to what circuitry lies downstream.

? It's my understanding that it doesn't happen quite like this.? My understanding is that the epoxy is hygroscopic, and its mass increases as it absorbs moisture.? The mass of epoxy swells, causing first crazing, then full cracking of the outer shell.? Leakage increases and

Relateable. That's the path most of us are on.

the resultant current flow causes heating, until it goes bang.? I believe the end stage there is thermal runaway.
??????????? -Dave

On 9/11/22 18:41, Tom Lee wrote:

Linear vs. SMPS would not be expected to matter, in any case. The problem is one of moisture ingress. The encapsulant shrinks and cracks over time, letting moisture in. At some point the capacitor breaks down and you get a multimedia spectacular. None of those processes is particularly sensitive to what circuitry lies downstream.

It's my understanding that it doesn't happen quite like this. My understanding is that the epoxy is hygroscopic, and its mass increases as it absorbs moisture. The mass of epoxy swells, causing first crazing, then full cracking of the outer shell. Leakage increases and the resultant current flow causes heating, until it goes bang. I believe the end stage there is thermal runaway.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Jeeze Chuck, my mistake, I thought you were talking about Rifas, not Schaffners. I've not seen a Schaffner go either, myself.

My grandmother used to say "I wish I'd been born rich instead of so beautiful!" ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

On Sun, Sep 11, 2022 at 03:41 PM, Tom Lee wrote:

Linear vs. SMPS would not be expected to matter, in any case.

Sure, as to whether the devices fail. I was speculating that the instruments with linear supplies would need less high frequency filtering on the mains.? (but I have a fairly small sample size of instrument types to judge that on)

开云体育

Nearly all of my blown RIFA caps have been in instruments with purely linear supplies. Indeed, a fair fraction of them have been in linear supplies!

Linear vs. SMPS would not be expected to matter, in any case. The problem is one of moisture ingress. The encapsulant shrinks and cracks over time, letting moisture in. At some point the capacitor breaks down and you get a multimedia spectacular. None of those processes is particularly sensitive to what circuitry lies downstream.

--Cheers,
Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070

Following up...

I think it was a firewall issue, though it mysteriously went away after checking the settings without (consciously) changing anything. After that, the update completed successfully.

The only problem is that I appear to have lost cal constants as a result of the earlier update failure -- at power up I get a "no synthesizer cal coefficients -- using defaults" message. I would like to ignore that, but there is a strong spur at about +300 kHz from the center frequency that wasn't there before. Still scratching my head what to do about that.

John
----

On Sun, Sep 11, 2022 at 01:08 PM, Dave McGuire wrote:

Are you perhaps conflating the Rifa capacitor problem with the bad electrolyte formula problem?

Well no, since I asked the question in the first post. I may be off with the time frame though. No one seems to have answered that question yet. Presumably this is an issue with SMPS instruments. My 80's HP gear has (AFAIK) almost all linear supplies.?

If you can't be pretty, may as well be lucky!

All I can say is in 4 decades of designing, using,
and repairing electronic equipment, I haven't seen
a Schaffner filter blow up. Tomorrow may be the day
that I may see a dozen...

The goodness of the whole idea of putting several
safety caps, which are designed to blow without
catching the instrument on fire, in a can full of tar
eludes me.

-Chuck Harris


On Sun, 11 Sep 2022 12:40:50 -0400 "Dave McGuire"
<mcguire@...> wrote:

On 9/11/22 11:53, Chuck Harris wrote:

Mostly the failure rate of RIFA paper dielectric safety
capacitors, with clear (yellow) epoxy potting, is related
to how large the difference is between their design failure
voltage, and the voltage applied.

In other words, for older capacitors:
If you use a 250VAC RIFA cap on 240VAC mains, failure is
all but assured.

If you use a 250VAC RIFA cap on 120V mains, you will likely
never see a failure.

That's nowhere near true in the field, unfortunately. I've
replaced two 250VAC RIFA capacitors run on 120V in the past week
alone. These blow up *all the time*.

Storage in a humid environment dramatically accelerates the
failure of RIFAs.

Or so says my 40 years of experience as an engineer, with never
seeing a single RIFA capacitor failure on 120VAC.

You've been lucky.

-Dave

On 9/11/22 15:57, vk2bea via groups.io wrote:

HP 3403C
I would have thought that this was manufactured before these caps were used. It looks like a late 70s / early 80s device. As I understand it these bad caps were more a late 80s / early 90s problem.

Are you perhaps conflating the Rifa capacitor problem with the bad electrolyte formula problem? Most of the Rifas I've seen blown up have been from the early 1980s.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

On Sun, Sep 11, 2022 at 11:26 AM, Susan Parker wrote:

HP 3403C

I would have thought that this was manufactured before these caps were used. It looks like a late 70s / early 80s device. As I understand it these bad caps were more a late 80s / early 90s problem.

Manufacturers part number.

This may be different from the model number or NSN as diferrent companies can make the same model instrument.

I have had a Schaffner filter (on a Phillips counter) fail, and have had a few instruments where they had cracked but not failed explosively.?
But I've had two problems with domestic equipment - a fan and a sewing machine. The manufacturers may wish consumers would change devices more often but the truth of it is that they'll be changed for fashion or failure? : they can't generally claim the equipment is obsolete and no longer useful, like they might with commercial equipment.

Thanks Chuck. I guess I have both factors in my favor here; 120VAC and low humidity in high desert country.

My HP 3403C True RMS Voltmeter's cap went with a bang and a nasty smell some years ago - at 245 Vac we are right at the top end of the UK "nominal" 230 Vac line voltage in this part of West London UK though so not overly surprising.
At the moment it is bouncing up and down by several hundred mV and the frequency is also jiggering about too, which is not reassuring.

John Ackermann N8UR <jra@...> writes:

On 9/11/22 13:42, Sven Schnelle wrote:

I would think that this bootloader is very similar to the PA-RISC HP-UX
machines. Lan paths are only listed if there's a DHCP server returning
a ip + bootserver + bootfile, and the TFTP server is responding. So make
sure that the network setup is properly working.
Also enable the autosearch flag. I think you can also say 'search
lan'
which would query the network regardless of the autosearch flag setting.

Thanks, Sven! I was wondering about the autosearch, but since I had
no idea what it did, was hesitant to mess with it.

I'm not sure just what the procedure is, but the "manual" process with
the HP E4406A firmware updater is to enter the MAC address in the
program, then tell the E4406A to boot from LAN; from that I would
gather that the updater program on the PC sets itself up as a TFTP
server listening for the MAC of the VSA.

Ah, ok. Yes, than it's very likely that the Updater program provides
DHCP + TFTP. Have you check your Windows firewall settings/logs, maybe
the packets get dropped?

'boot lan' should also be possible to explicitely trigger a boot from lan.