Re: Shorted large filter cap - don't they normally go open?
Hi,
thanks for all these stories.
Although the PSU was running for 20 minutes or so, I did not observe any signs of heat or smell. The only thing was the dark goo around the screws.
Could it have vented during this period? There is a little white deposit on the blank soldered parts around, but not on the wires or elsewhere. Power consumption of the PSU wasn't higher than expected, and the 5V rail must have been OK otherwise the analyser would have stalled.
When the cap shorted the pre-regulator shut down and periodically tried to start up. No fuse was blown. Not a bad design from that point of view.
I'll try to reform the cap with Dave's receipt, although it shouldn't work...
cheers
Martin
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Re: HP 312A wave analyser
10 years (half life of the Krypton 85 they sometimes stick in neon bulbs, depending on the bulb specification.)
I have finally found the problem with the display on my 312A, on the MHZ range nixie, the 2nd from the first LHS, the neon that drives the photo conductor is flickering. How many hours, or years, of operation does it take before the neon strike voltage point begins to degrade? I may have to start looking at LED substitutes, which I remember being discussed in a previous thread, and clean the range selector switch with de-oxit ? ? ? ? ? ? ? ? ? ? ? ? ? ? Regards Brad?
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Re: HP 312A wave analyser
I have finally found the problem with the display on my 312A, on the MHZ range nixie, the 2nd from the first LHS, the neon that drives the photo conductor is flickering. How many hours, or years, of operation does it take before the neon strike voltage point begins to degrade? I may have to start looking at LED substitutes, which I remember being discussed in a previous thread, and clean the range selector switch with de-oxit ? ? ? ? ? ? ? ? ? ? ? ? ? ? Regards Brad?
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Re: Shorted large filter cap - don't they normally go open?
Yep, I too have found low voltage "large value" electrolytic cap's self-depolarise if left unused for some years (10+!)
If you suddenly hit them with the full operating voltage (and ripple current) the resulting heat generated internally can result in the infamous "smelly snow storm" as the insides are ejected via the vent, or explosively by firing the entire end cap off the can!
Or, the internal distort and go short cct.? Also sometimes creating a lot of heat and pressure, but usually something else up-stream opens up, hopefully a fuse of circuit breaker first.
I have though had fair success in recovering them, but you need to check them "BEFORE" applying main power.
The last I recovered (some years ago, based on previous experience with HV electrolytics) were a bank of three 31000uF/40V caps, from a very old computer PSU.
When checked with a meter, they were virtually short cct.? (All three, individually!)
As I wished to use them as a bank of three again, I set up a lab PSU (with diode & fuse in series on the output) for some 41V, and less than 25mA current limit.
It took several months (4+!) before the current limit light went out, but they came back to life (as indicated by slowly rising terminal voltage) and are happy again with low leakage running at some 28V average (37V peak) running stone cold.? Also their "capacity" is not far above 100,000uF total again.?? Didn't measure ESR, but the way things were working, and cool with it, I don't think there is an issue there.? (The application was an 18V raw DC PSU, upstream of several DC/DC buck converters.)
The disadvantage with this, is the time it takes.? The slower the better.? (If the terminal voltage does not start to rise after some days, or stays at a low level without moving (or even fall's back!) Then it's probably not going to recover.)
Small wire ended electrolytic cap's also suffer, but the useful recovery rate is abysmal.? There again, the replacements are much more economic than trying to source those "bin sized" monsters.
This is based on my own experience over the years.
Remember too, that a large value cap with even a moderate voltage, stores a considerable amount of energy, that at best can cause damage to other things,? At worst, well...? Take care.
Dave G8KBV
--
Created on and sent from a Unix like PC running and using free and open source software:
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Re: Shorted large filter cap - don't they normally go open?
I¡¯ve had a big Sprague electrolytic in a lab supply, 60s vintage, fail in a Zener-like mode. Up to a couple volts it was fine, then its differential resistance dropped pretty much to zero per curve tracer.
I also was not quite expecting that.
Cheers, Kuba
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21 mars 2023 kl. 4:52 fm skrev Martin via groups.io <musaeum@...>:
?Hi all, a W&G switching power supply in my SNA1 spectrum analyzer had a large 15mF filter cap with a total short. The screws showed some brown-black goo, otherwise no sign of failure like overheating. Another capacitor of the same type is perfectly in spec. Once the capacitor replaced the supply and the rest seems to work fine. Up to now I thought these caps gradually loose capacity and go open. Here is the first time I've seen one shorted. The supply worked for 20 minutes or so before it failed. Before that it was unused for years, and when switched on it was stressed by a shorted through capacitor in the -12V supply. The 15mF capacitor belongs to the 5V supply, probably unrelated. Any opinion on this? cheers Martin
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Re: Shorted large filter cap - don't they normally go open?
On Tue, Mar 21, 2023 at 11:24?AM Martin Rickes < MRickes@...> wrote: Hi Martin,
I had this several times already. Last time in the PSU of an old HP DSO.? That one failed quite spectacularly?(masclet¨¢!!!) before the circuit-braker?kicked in. It's rare, yes, but not impossible :-)
in my experience not so rare actually. I had at least 4 electrolytics failing short on HP and Schlumberger instruments? (470 to 1000 uF filter capacitors on DC supply rails) and in one occasion, 4 big 10000uF 63V capacitors going short circuit on an audio amplifier's DC power rails. These could be temporarily fixed by slowly increasing the DC voltage across the capacitors. But the capacitor would fail again shorted after a few weeks if left unpowered. ?These would kill 10 amps fuses in a quite "loud" way until all of them were replaced.
HTH Frank IZ8DWF
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Re: Shorted large filter cap - don't they normally go open?
Hi Martin,
I had this several times already. Last time in the PSU of an old HP DSO.? That one failed quite spectacularly?(masclet¨¢!!!) before the circuit-braker?kicked in. It's rare, yes, but not impossible :-)
Cheers, Martin
Hi all,
a W&G switching power supply in my SNA1 spectrum analyzer had a large 15mF filter cap with a total short. The screws showed some brown-black goo, otherwise no sign of failure like overheating. Another capacitor of the same type is perfectly in spec. Once the capacitor replaced the supply and the rest seems to work fine.
Up to now I thought these caps gradually loose capacity and go open. Here is the first time I've seen one shorted. The supply worked for 20 minutes or so before it failed. Before that it was unused for years, and when switched on it was stressed by a shorted through capacitor in the -12V supply. The 15mF capacitor belongs to the 5V supply, probably unrelated.
Any opinion on this?
cheers
Martin
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Re: Fixed my HP 5345A today!!
Can we please start a new topic, rather than continuing to use the same old, now misleading Subject line? None of the last 10 respondents said anything about the HP 5345A. 73 de Brian, VK2GCE
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Re: Fixed my HP 5345A today!!
Which way is the pointy end of the nail facing??? ? Not familiar with that statement? Nigel ?
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From: [email protected] <[email protected]> On Behalf Of Noel VK3NH
Sent: 21 March 2023 00:00
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] Fixed my HP 5345A today!!? Yep that's a typo Marconi 2042 indeed, the low noise version.?
You may be a good contact for password/recalibration information.
Which way is the pointy end of the nail facing?
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Shorted large filter cap - don't they normally go open?
Hi all, a W&G switching power supply in my SNA1 spectrum analyzer had a large 15mF filter cap with a total short. The screws showed some brown-black goo, otherwise no sign of failure like overheating. Another capacitor of the same type is perfectly in spec. Once the capacitor replaced the supply and the rest seems to work fine. Up to now I thought these caps gradually loose capacity and go open. Here is the first time I've seen one shorted. The supply worked for 20 minutes or so before it failed. Before that it was unused for years, and when switched on it was stressed by a shorted through capacitor in the -12V supply. The 15mF capacitor belongs to the 5V supply, probably unrelated. Any opinion on this? cheers Martin   
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Re: Fixed my HP 5345A today!!
Yep that's a typo Marconi 2042 indeed, the low noise version.?
You may be a good contact for password/recalibration information.
Which way is the pointy end of the nail facing?
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Re: HP 3585B Looking for mating connector
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Re: low amplitude readings below 10MHz on a 8591E
That suggests a very strong LO? signal ¨Ca good thing so probably not a YTO fault, Just to clarify.. ? CAL FREQUENCY passes CAL AMPTD ¨Cpasses with CAL link in place? CONFIDENCE TEST? ? ? Mike ? ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 20 March 2023 19:50
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi Mike its? 10dBm above the ref lvl. with 10 db ATTEN ? Gr Kees, Did you take a look at the 0hz feedthrough amplitude ¨C(left side of display) What value ?is it? Mike ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 20 March 2023 19:28
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi Mike, I've backup the constants ( paper) and used my marconi frequency?generator?to have the amptd NOT fail. After that the cal signal of the 8591E was used to do an amptd again and this time it succeeded. Still the lower end is terrible ( low amplitude ). I've done the service diag and? 1. the MAIN Coil driver?is much steeper and starts higher at the -20dbm horizontal line? The rest has the same picture as shown in the?8590-90316 manual. So according to the manual it's in the A7 board. does somebody have a spare will to sell ? Hi ?in your case ?from 238-247 if you haven¡¯t done it already? ..201 onwards? ?backing up correction constants ? One thing to check is the level of your LO feedthrough amplitude ?..the signal at 0hz on the left hand edge of the display Do frequency 0hz? span 1mhz¡ and see what the level of the LO is? --good ones are around -10db or better. ? By the way you¡¯re 8591? is a bit different on the front end than the 8590e series , yours is more prone to mixer failure but can be fixed . Lots of info on you tube ? Regards Mike g4wam ? ? ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 17:47
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ?
got it and will start reading.?
Any recommendations about what paragraph? ? You need 08590-90316? from? 2001 8590 series Service Guide ? Are large tome but worth downloading or buying ¸é±ð²µ²¹°ù»å¡¯²õ Mike g4wam ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 14:41
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi, Are we talking about the user manual 08590-90301, because there is not much cal data in it other than the normal stuff. I also have the installation, verification & Operation manual. Or are there other manual I need?
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Re: low amplitude readings below 10MHz on a 8591E
Hi Mike its? 10dBm above the ref lvl. with 10 db ATTEN
Gr. Kees
Gr Kees, Did you take a look at the 0hz feedthrough amplitude ¨C(left side of display) What value ?is it? Mike ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 20 March 2023 19:28
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi Mike, I've backup the constants ( paper) and used my marconi frequency?generator?to have the amptd NOT fail. After that the cal signal of the 8591E was used to do an amptd again and this time it succeeded. Still the lower end is terrible ( low amplitude ). I've done the service diag and? 1. the MAIN Coil driver?is much steeper and starts higher at the -20dbm horizontal line? The rest has the same picture as shown in the?8590-90316 manual. So according to the manual it's in the A7 board. does somebody have a spare will to sell ? Hi ?in your case ?from 238-247 if you haven¡¯t done it already? ..201 onwards? ?backing up correction constants ? One thing to check is the level of your LO feedthrough amplitude ?..the signal at 0hz on the left hand edge of the display Do frequency 0hz? span 1mhz¡ and see what the level of the LO is? --good ones are around -10db or better. ? By the way you¡¯re 8591? is a bit different on the front end than the 8590e series , yours is more prone to mixer failure but can be fixed . Lots of info on you tube ? Regards Mike g4wam ? ? ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 17:47
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ?
got it and will start reading.?
Any recommendations about what paragraph? ? You need 08590-90316? from? 2001 8590 series Service Guide ? Are large tome but worth downloading or buying ¸é±ð²µ²¹°ù»å¡¯²õ Mike g4wam ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 14:41
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi, Are we talking about the user manual 08590-90301, because there is not much cal data in it other than the normal stuff. I also have the installation, verification & Operation manual. Or are there other manual I need?
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Re: low amplitude readings below 10MHz on a 8591E
Gr Kees, Did you take a look at the 0hz feedthrough amplitude ¨C(left side of display) What value ?is it? Mike ? ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 20 March 2023 19:28
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi Mike, I've backup the constants ( paper) and used my marconi frequency?generator?to have the amptd NOT fail. After that the cal signal of the 8591E was used to do an amptd again and this time it succeeded. Still the lower end is terrible ( low amplitude ). I've done the service diag and? 1. the MAIN Coil driver?is much steeper and starts higher at the -20dbm horizontal line? The rest has the same picture as shown in the?8590-90316 manual. So according to the manual it's in the A7 board. does somebody have a spare will to sell ? Hi ?in your case ?from 238-247 if you haven¡¯t done it already? ..201 onwards? ?backing up correction constants ? One thing to check is the level of your LO feedthrough amplitude ?..the signal at 0hz on the left hand edge of the display Do frequency 0hz? span 1mhz¡ and see what the level of the LO is? --good ones are around -10db or better. ? By the way you¡¯re 8591? is a bit different on the front end than the 8590e series , yours is more prone to mixer failure but can be fixed . Lots of info on you tube ? Regards Mike g4wam ? ? ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 17:47
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ?
got it and will start reading.?
Any recommendations about what paragraph? ? You need 08590-90316? from? 2001 8590 series Service Guide ? Are large tome but worth downloading or buying ¸é±ð²µ²¹°ù»å¡¯²õ Mike g4wam ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 14:41
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi, Are we talking about the user manual 08590-90301, because there is not much cal data in it other than the normal stuff. I also have the installation, verification & Operation manual. Or are there other manual I need?
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Re: low amplitude readings below 10MHz on a 8591E
Hi Mike, I've backup the constants ( paper) and used my marconi frequency?generator?to have the amptd NOT fail. After that the cal signal of the 8591E was used to do an amptd again and this time it succeeded.
Still the lower end is terrible ( low amplitude ). I've done the service diag and? 1. the MAIN Coil driver?is much steeper and starts higher at the -20dbm horizontal line? The rest has the same picture as shown in the?8590-90316 manual. So according to the manual it's in the A7 board. does somebody have a spare will to sell or is too premature.
Gr Kees
Hi ?in your case ?from 238-247 if you haven¡¯t done it already? ..201 onwards? ?backing up correction constants ? One thing to check is the level of your LO feedthrough amplitude ?..the signal at 0hz on the left hand edge of the display Do frequency 0hz? span 1mhz¡ and see what the level of the LO is? --good ones are around -10db or better. ? By the way you¡¯re 8591? is a bit different on the front end than the 8590e series , yours is more prone to mixer failure but can be fixed . Lots of info on you tube ? Regards Mike g4wam ? ? ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 17:47
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ?
got it and will start reading.?
Any recommendations about what paragraph? ? You need 08590-90316? from? 2001 8590 series Service Guide ? Are large tome but worth downloading or buying ¸é±ð²µ²¹°ù»å¡¯²õ Mike g4wam ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KeesHofwegen
Sent: 18 March 2023 14:41
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] low amplitude readings below 10MHz on a 8591E ? Hi, Are we talking about the user manual 08590-90301, because there is not much cal data in it other than the normal stuff. I also have the installation, verification & Operation manual. Or are there other manual I need?
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HP 3585B Looking for mating connector
Does anyone in the group know or have a part number for a mating power connector for the probe power receptacle on the HP3585B. The manual only gives the part number for the receptacle. ?I think it¡¯s also similar to the power connector on the 8590 series analyzers. ?This is the low voltage connector used to power things like active probes. Thanks.
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Re: Fixed my HP 5345A today!!
One very minor point, if I may, could the Marconi Sig Gen be a 2042?
There were no 404x anything in the Marconi range as far as I am aware... Unless you have discovered something magically unknown. Just being picky ? Regards Nigel Adams - Marconi Instruments Heritage Collection? by banging a nail into a piece of wood...
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On 20 Mar 2023, at 05:13, ChrisBeee via < chrisbeee@...> wrote: ---with a Marconi 4042 signal generator is not going to be rolling anywhere now its sunk into the carpet. ---
...reminds me of the movie 'China Syndrome' :-)
Even large dual caster wheels waive the white flag here, don't ask me how I know...
Chris
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Re: Fixed my HP 5345A today!!
---with a Marconi 4042 signal generator is not going to be rolling anywhere now its sunk into the carpet. ---
...reminds me of the movie 'China Syndrome' :-)
Even large dual caster wheels waive the white flag here, don't ask me how I know...
Chris
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Re: Fixed my HP 5345A today!!
Hi guys,
Now here is a topic I can really relate to being 71 nearing 72.? ?Who needs to go to the gym?
Lifting HP 70,000 mainframes Tek scopes and other test gear on to the top shelf of my test bench in the screened room is "interesting".? What could possibly go wrong?
Then you have to climb up on the bench to get at the cables at the back.? power/reference and HPIB.
The mobile mini-trolley at the side of the test bench loaded with H/P DC power supply, H/P 8642M, HP8663A, H/P70004 mainframe plus 2x HP70001 mainframes fully loaded as a 4 function test system and topped off with a Marconi 4042 signal generator is not going to be rolling anywhere now its sunk into the carpet.? But I can at least walk around the back to change/check the connections. One plus side is the H/P 70,000s are modular so I can swap out a module if the unit has issues.
cheers Noel (from Australia down under)
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Martin
Martin Rickes
Brian
Noel VK3NH