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Hi all, figure a good old repair attempt would be a good 1st post.
I bought a broken E4404B SA in hopes to repair it. The seller said it has a dead PSU, but doesn't know if it has any other failures.
I took the PSU out to test it. I decided to test all the MOSFETs and the 2 optocouplers, all tested good.
Then I realized since this PSU can take DC input, I can just supply 12VDC and see if the DC-DC converter secondary side work. And it DOES. All voltage rails (+28V, +15V. +5V. -5V, -15V, fan) are all present. Draws about 5-6W which seems alright.
Which narrows down the failure to the AC mains sides. I checked the mains side, the 2 bulk caps hold a total of about 310VDC, which matches with the peak of rectified mains AC.
When I force the supply on while connect to mains, I hears a small click every second. Measurements of the DC rails shows them varying greatly. It's like the PSU is trying to start up but can't.
Will update with any progress and pictures soon.
Also, as I was testing the PSU, one of the RIFA caps exploded, filling my room with smoke and cover the PCB in tars. Horrible
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Are RIF caps still used in new equipment, or have manufacturers found better solutions?
Thanks KI4QCK Allen Hill
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On Apr 22, 2024, at 2:55?PM, Nick Stanley <rosewardxiii@...> wrote:
?Hi all, figure a good old repair attempt would be a good 1st post.
I bought a broken E4404B SA in hopes to repair it. The seller said it has a dead PSU, but doesn't know if it has any other failures.
I took the PSU out to test it. I decided to test all the MOSFETs and the 2 optocouplers, all tested good.
Then I realized since this PSU can take DC input, I can just supply 12VDC and see if the DC-DC converter secondary side work. And it DOES. All voltage rails (+28V, +15V. +5V. -5V, -15V, fan) are all present. Draws about 5-6W which seems alright.
Which narrows down the failure to the AC mains sides. I checked the mains side, the 2 bulk caps hold a total of about 310VDC, which matches with the peak of rectified mains AC.
When I force the supply on while connect to mains, I hears a small click every second. Measurements of the DC rails shows them varying greatly. It's like the PSU is trying to start up but can't.
Will update with any progress and pictures soon.
Also, as I was testing the PSU, one of the RIFA caps exploded, filling my room with smoke and cover the PCB in tars. Horrible
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On 4/22/24 15:22, Allen Hill via groups.io wrote: Are RIF caps still used in new equipment, or have manufacturers found better solutions? The common RIFA capacitor failure is a materials problem, which was solved long ago. Later RIFA capacitors do not exhibit the explosion problem. Many companies manufacture safety capacitors. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Yes, I've bought new RIFA caps to replace the old ones.? WIMA and Kemet are two other brands that make the safety rated X and Y caps.
But I don't replace old RIFAs on sight anymore.? Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land.? Those in 240 VAC land risk explosions, though.
HTH.
Jim Ford Laguna Hills, California, USA
"And we know that God causes all things to work together for the good of those who love God and are called according to his purpose for them." Romans 8:28 (NLT)
------ Original Message ------
Date 4/22/2024 2:27:58 PM
Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair
On 4/22/24 15:22, Allen Hill via groups.io wrote:
Are RIF caps still used in new equipment, or have manufacturers found better solutions?
?
The common RIFA capacitor failure is a materials problem, which was solved long ago. Later RIFA capacitors do not exhibit the explosion problem. Many companies manufacture safety capacitors.
?
-Dave
?
-- Dave McGuire, AK4HZ
New Kensington, PA
?
?
?
?
?
|
having had quite a few
go here in 120 VAC land...if I am in the equipment I replace (or at least remove )
especially if easy access and they are yellow before the stench
and mess....I cannot stand the stench or the mess which is the
worst part. btw the stench is not so bad in summer or when
weather allows windows and doors open...winter is another
matter...and when do they like to fail.......
搁别苍é别
Northern California Mtns
On 4/22/24 11:07 AM, Jim Ford via
groups.io wrote:
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Show quoted text
Yes, I've bought new RIFA caps to replace the old ones.? WIMA
and Kemet are two other brands that make the safety rated X and
Y caps.
But I don't replace old RIFAs on sight anymore.? Too much
collateral damage by a ham-fisted engineer with a soldering iron
in his hand, and explosions are rare here in 120 VAC land.?
Those in 240 VAC land risk explosions, though.
HTH.
Jim Ford
Laguna Hills, California, USA
"And we know that God causes all things to work together
for the good of those who love God and are called according
to his purpose for them." Romans 8:28 (NLT)
------ Original Message ------
Date 4/22/2024 2:27:58 PM
Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B
Spectrum Analyzer With Dead PSU Repair
On 4/22/24 15:22, Allen Hill via
groups.io wrote:
Are RIF caps still used in new
equipment, or have manufacturers found better solutions?
?
The common RIFA capacitor failure is
a materials problem, which was solved long ago. Later RIFA
capacitors do not exhibit the explosion problem. Many
companies manufacture safety capacitors.
?
-Dave
?
-- Dave McGuire, AK4HZ
New Kensington, PA
?
?
?
?
?
|
On 4/22/24 14:07, Jim Ford wrote: But I don't replace old RIFAs on sight anymore.? Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land.? Those in 240 VAC land risk explosions, though. Uh, I've had three go so far just this year. The risk is surely higher in 240V-land, but I strongly advise replacing them on sight here too. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
I suspect you live in lightning country, Dave. Southern California where I live is just about the least likely place on the planet for lightning strikes. After damaging at least 2 instruments in the process of replacing (old) RIFAs, I'm not risking that again. YMMV.
Jim
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Show quoted text
------ Original Message ------ From "Dave McGuire" <mcguire@...> To [email protected]Date 4/22/2024 4:12:11 PM Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair On 4/22/24 14:07, Jim Ford wrote:
But I don't replace old RIFAs on sight anymore. Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land. Those in 240 VAC land risk explosions, though. Uh, I've had three go so far just this year. The risk is surely higher in 240V-land, but I strongly advise replacing them on sight here too.
-Dave
-- Dave McGuire, AK4HZ
New Kensington, PA
|
Pittsburgh, not much lightning here.
Nearly every Rifa capacitor I see is swollen and crazed, and when you see that, detonation isn't far behind.
-Dave
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Show quoted text
On 4/22/24 17:55, Jim Ford wrote: I suspect you live in lightning country, Dave.? Southern California where I live is just about the least likely place on the planet for lightning strikes.? After damaging at least 2 instruments in the process of replacing (old) RIFAs, I'm not risking that again.? YMMV.
Jim
------ Original Message ------
From "Dave McGuire" <mcguire@...>
To [email protected]
Date 4/22/2024 4:12:11 PM
Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair
On 4/22/24 14:07, Jim Ford wrote:
But I don't replace old RIFAs on sight anymore.? Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land.? Those in 240 VAC land risk explosions, though. ? Uh, I've had three go so far just this year.? The risk is surely higher in 240V-land, but I strongly advise replacing them on sight here too.
?????????? -Dave
-- Dave McGuire, AK4HZ
New Kensington, PA
--
Dave McGuire, AK4HZ
New Kensington, PA
|
I'm sorry Jim, I didn't mean to sound disagreeable. I typed and sent that too fast.
Rifa problems are caused by moisture absorption, not line voltage or lightning. This is a very well-known and understood thing everywhere. We deal with it all the time at the museum.
-Dave
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Show quoted text
On 4/22/24 19:59, Dave McGuire wrote: ? Pittsburgh, not much lightning here.
? Nearly every Rifa capacitor I see is swollen and crazed, and when you see that, detonation isn't far behind.
?????????? -Dave
On 4/22/24 17:55, Jim Ford wrote:
I suspect you live in lightning country, Dave.? Southern California where I live is just about the least likely place on the planet for lightning strikes.? After damaging at least 2 instruments in the process of replacing (old) RIFAs, I'm not risking that again.? YMMV.
Jim
------ Original Message ------
?From "Dave McGuire" <mcguire@...>
To [email protected]
Date 4/22/2024 4:12:11 PM
Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair
On 4/22/24 14:07, Jim Ford wrote:
But I don't replace old RIFAs on sight anymore.? Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land.? Those in 240 VAC land risk explosions, though. ? Uh, I've had three go so far just this year.? The risk is surely higher in 240V-land, but I strongly advise replacing them on sight here too.
?????????? -Dave
-- Dave McGuire, AK4HZ
New Kensington, PA
--
Dave McGuire, AK4HZ
New Kensington, PA
|
No worries. We can still be friends! LOL!
Jim
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Show quoted text
------ Original Message ------ From "Dave McGuire" <mcguire@...> To [email protected]Date 4/22/2024 7:05:37 PM Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair
I'm sorry Jim, I didn't mean to sound disagreeable. I typed and sent that too fast.
Rifa problems are caused by moisture absorption, not line voltage or lightning. This is a very well-known and understood thing everywhere. We deal with it all the time at the museum.
-Dave
On 4/22/24 19:59, Dave McGuire wrote:
Pittsburgh, not much lightning here.
Nearly every Rifa capacitor I see is swollen and crazed, and when you see that, detonation isn't far behind.
-Dave
On 4/22/24 17:55, Jim Ford wrote:
I suspect you live in lightning country, Dave. Southern California where I live is just about the least likely place on the planet for lightning strikes. After damaging at least 2 instruments in the process of replacing (old) RIFAs, I'm not risking that again. YMMV.
Jim
------ Original Message ------
From "Dave McGuire" <mcguire@...>
To [email protected]
Date 4/22/2024 4:12:11 PM
Subject Re: [HP-Agilent-Keysight-equipment] Agilent E4404B Spectrum Analyzer With Dead PSU Repair
On 4/22/24 14:07, Jim Ford wrote:
But I don't replace old RIFAs on sight anymore. Too much collateral damage by a ham-fisted engineer with a soldering iron in his hand, and explosions are rare here in 120 VAC land. Those in 240 VAC land risk explosions, though. Uh, I've had three go so far just this year. The risk is surely higher in 240V-land, but I strongly advise replacing them on sight here too.
-Dave
-- Dave McGuire, AK4HZ
New Kensington, PA
-- Dave McGuire, AK4HZ
New Kensington, PA
|
Hi Nick,
First I would check after removing the old RIFA is the reservoir capacitor for the switching regulator. It is not uncommon problem that these go low in capacitance, and stops the psu from starting.
Regards, Askild
On Mon, Apr 22, 2024 at 8:55?PM Nick Stanley via <rosewardxiii= [email protected]> wrote: Hi all, figure a good old repair attempt would be a good 1st post.
I bought a broken E4404B SA in hopes to repair it. The seller said it has a dead PSU, but doesn't know if it has any other failures.
I took the PSU out to test it. I decided to test all the MOSFETs and the 2 optocouplers, all tested good.
Then I realized since this PSU can take DC input, I can just supply 12VDC and see if the DC-DC converter secondary side work. And it DOES. All voltage rails (+28V, +15V. +5V. -5V, -15V, fan) are all present. Draws about 5-6W which seems alright.
Which narrows down the failure to the AC mains sides. I checked the mains side, the 2 bulk caps hold a total of about 310VDC, which matches with the peak of rectified mains AC.
When I force the supply on while connect to mains, I hears a small click every second. Measurements of the DC rails shows them varying greatly. It's like the PSU is trying to start up but can't.
Will update with any progress and pictures soon.
Also, as I was testing the PSU, one of the RIFA caps exploded, filling my room with smoke and cover the PCB in tars. Horrible
|
The E440* PSU is a less well known topology (CUK) compared to the usual flybacks we see. Probably made sense for the 12V-in capability. I'd be very curious to see a schematic of these, but I don't think an official one exists ?
+1 for replacing RIFAs on sight, although I don't think they're the cause here.
I've rarely found bulk caps to be the problem; while possible, it wouldn't be the first thing I check. Now on a flyback I would look for the (small-ish) "startup cap", an electrolytic on the primary side that serves to power the controller IC. Can't say for sure if the same is applicable on this one, but I would take a close look at any small lytics on the primary side.
You could look at the IC supply rails ( I see a 339 comparator, LT1121 linear (!) regulator, and U6 near an opto but can't read the markings), they will probably be pulsating with the 'click' you're hearing.
*** Don't probe anything on the primary side with a plain oscilloscope !! unless you know exactly why and how not to kill your scope and/or yourself ***
I don't know how this architecture operates, but it's not impossible that the minimum load requirement would be different in AC or DC mode; have you tried connecting something to the 5V standby rail ?
There is some related info here:
https://www.eevblog.com/forum/repair/hpagilentkeysight-e4403b-repair/
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The 310VDC on the bulk caps are present even during the click, dipping only to 295V when click is heard. Measured them and they look fine to. So probably not the problem.
I've just check the primary side actually. Monitoring the 3 ICs (PWM controller, LT 1121 regulator and LM339) supply voltages I found them to fluctuate wildly with the clicking sound (12-18V I believe), causing the entire section of that board (which I assume is the primary side controller) to power on briefly before turning off again. I'm tracing out the controller supply rail right now to see where it leads.
Also I've removed all the X2 RIFA caps, they're for EMI so it's probably ok to not have them for now.
I have not tried to load the 5V std by rail yet, but will keep that in mind.
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On Tue, Apr 23, 2024 at 11:06 AM, Nick Stanley wrote:
nt even during the click, dipping only to 295V when
Rifa caps is a good preventative maintenance but the issue is most likely a small startup capacitor near the controller IC. These dry out and will not have the correct voltage feeding the controller IC. The ic tries to start and then the cap cant give enough stored energy and you hear the clicking as that repeats itself. Very common issue on switching supplies.? Not likely the bulk caps are the issue,? Best to discharge all the caps and test with ESR meter.? Focus on the area of the controller chip.? Maciej?
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On Tuesday 23 April 2024 09:40:09 am fenugrec via groups.io wrote: *** Don't probe anything on the primary side with a plain oscilloscope !! unless you know exactly why and how not to kill your scope and/or yourself ***
That's when you want to use an isolation transformer... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
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After a bit of reading I sort of understand the start up procedure of a typical SMPS. A start up capacitor is charged from rectified mains, usually via a power resistor. This cap is connected to the controller circuit supply rail. When the psu is turned on and the caps is charged enough, the controller is turned on and starts driving the main switching transformer via a power MOSFET. On the main switch transformer, a small secondary winding output is rectified and fed to the controller circuit, this will now power the controller instead of the small start up cap.
I managed to ID the startup cap, which measured fine.
I then probe 2 points, the PWM controller supply pin(fed from a LT1121 regulator) and the secondary winding output.
The scope shows that the startup cap circuit works fine. But the output of the secondary winding isn’t. It only shows oscillation for about 50ms before disappearing, causing the circuit to shut down and restart. I’ll do more probing around the controller, driver section tonight.
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Apologize for the 2MB size photos, I was in a rush.
And also, the SMPS was powered from an isolation transformer?
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On 2024-04-22, at 20:19, Nick Stanley <rosewardxiii@...> wrote:
Also, as I was testing the PSU, one of the RIFA caps exploded, filling my room with smoke and cover the PCB in tars. Horrible
Welcome to the club. Even if you have removed all the RIFA caps now, there are still electrolytics of unknown status, so here is my PSA for the day: *** Do wear eye protection when working on power supplies or other high-energy electronics *** (And, please, don’t think the mere presence of an isolation transformer makes mains voltages suddenly safe to work on, neither with respect to electric shocks nor with respect to unplanned high-energy short-circuits..) Grü?e, Carsten
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Hello Nick,
What is the startup cap ? Is it the group of two 680?F capacitors C189 & C190 ?
Best regards
Eric
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Dave McGuire
fenugrec
