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  1. HP8924-Family-Spectrum-Analyzers
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8924C POWER SUPPLY DEAD

 

Greetings all,
It looks like the power supply in my 8924C has died. The green light does not even come on. The fuse is ok. Any ideas? Is there anyone out there repairing them as I cannot find any info on the supply. Any help is greatly appreciated. Thanks,

Mike, WA9FDO
 

Rick at Amtronix (do a Google search) has helped me in the past with this issue. I highly recommend him and I am not associated with him or his busines. Just another happy customer.


On Thu, Nov 17, 2022 at 7:26 PM, mike_wa9fdo
<serc1mp@...> wrote:
Greetings all,
It looks like the power supply in my 8924C has died. The green light does not even come on. The fuse is ok. Any ideas? Is there anyone out there repairing them as I cannot find any info on the supply. Any help is greatly appreciated. Thanks,

Mike, WA9FDO

 

There was a document floating around ...should be in the files section ...on repairing the 8924 power supply.

basically a thousand screws later there is a small cap on the daughter board inside the supply.that usually fails.

This is the standby supply ( green LED) that is on all the time?

Normally everything else is fine.
 

¿ªÔÆÌåÓý



On Nov 17, 2022, at 8:49 PM, jyelmgren <jyelmgren@...> wrote:

?There was a document floating around ...should be in the files section ...on repairing the 8924 power supply.

basically a thousand screws later there is a small cap on the daughter board inside the supply.that usually fails.

This is the standby supply ( green LED) that is on all the time?

Normally everything else is fine.

 

Replace the electrolytic capacitors with high current 105 degree C or better.

73
Glenn
WB4UIV
 

You can try this attached PDF for starters.
?
Ralph ku4pt
?

Repairing the 8924 Power Supply.pdf
Repairing the 8924 Power Supply.pdf

 

Thanks to all for your help. Looked up the suggested file, and that was the problem. Replaced the cap and everything is back in operation.

Mike, WA9FDO
 

I just fixed my second power supply replacing that cap.? All the files with pictures and procedures are in the files section.??

Pat
 

I can add a "me too".? My power supply died in 2009 and I paid someone to fix it, it just died again and this time I decided to tackle it myself this time.

So far I've confirmed that was the problem by providing +15V from an external bench supply as suggested in the PDF.? That made it possible to turn on and all of the self tests passed!? (Whew !)

Two possibly new pieces of information for anyone running into this problem:

1. After disconnecting the bench supply and turning the power "off" I still measure a perfect 15.00 volts on standby and it turned back on successfully.
2. My green LED still lights up even with the bad +15v (I measured 4.9V), but it's a LOT brighter at 15V.? So if your LED is still lit do not assume that the cap on the standby board is not the problem.

73's Skip WB6YMH
 

Hi all,
?
My 8924C died as well. Thankfully the excellent PDF and a $0.40 47 uF, 50 v high temp electrolytic fixed it.? What I will say is that you can remove and replace that cap in situ if you are gentle and patient.? An electric screw driver is very useful.
?
73
de VK6XRE
 

When my 8924C died a few years ago, it was the little supply that keeps the OCXO warmed up. The rest of it wouldn't work without that. Getting to that little supply was a headache, but a couple of caps fixed it.
The last time it died has been a total nightmare. Swapping boards from my 8924E only made both of them bad. A second replacement board got it working, sort of. It still says it has bad cal data, but seems to work otherwise. The power supply of the 8924E blew up. I still need to address both issues.


On Sun, Dec 31, 2023 at 3:34?AM Robyn Edwards <vk6xre@...> wrote:
Hi all,
?
My 8924C died as well. Thankfully the excellent PDF and a $0.40 47 uF, 50 v high temp electrolytic fixed it.? What I will say is that you can remove and replace that cap in situ if you are gentle and patient.? An electric screw driver is very useful.
?
73
de VK6XRE
 

Hi Robyn,

I see we are both VK6 ... and proud owners of these great instruments. I have been into the PSU?on my 8920A also.? At last all is going sweet.?

?Perhaps we could support each other with some local dialogue.

?I am QTHR and a member of NCRG.

Regards

Bill M.

?

On 29/12/2023 7:24 am, Robyn Edwards wrote:

Hi all,
?
My 8924C died as well. Thankfully the excellent PDF and a $0.40 47 uF, 50 v high temp electrolytic fixed it.? What I will say is that you can remove and replace that cap in situ if you are gentle and patient.? An electric screw driver is very useful.
?
73
de VK6XRE
 

Hi Bill,

I have an 8920 and the power supply is also dead. A fellow ham said he could fix it - but that is now 2 years ago. I know nothing about switchmode power supplies so am not prepared to touch it. I replaced all caps but had no luck.

I'm in VK5 land. Is there anyone over there that has experience with switchmode supplies ?

Regards,

Dean
VK5HMV
 

Confirming the usual, replacing the 47 uF fixed it.?

That capacitor had been replaced in 2009. I don't use my 8924C regularly, but it's been plugged in 24/7 since 2009 "just in case".?

I really don't want to do this again so I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.

73's Skip WB6YMH
 
Edited

?
Good idea to not leave it on.? 14 years of solid ON is really extreme and probably a "personal best" for all of us gathered here.EmojiEmoji
______________________________________________________________
?
On Tuesday, January 9, 2024 at 05:44:17 PM EST, Skip wrote:
?
... I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.

?
 

With the 8924C, leaving it on is quite different to leaving it plugged in. I can understand not leaving it on. Besides the wear and tear, it consumes a fair amount of power, and more importantly to me, it is quite noisy. Leaving it plugged in, keeps the OCXO warm, and ready for use. It is meant to stay plugged in all the time.

On Tue, Jan 9, 2024 at 10:57?PM Hank Riley via <n1ltv=[email protected]> wrote:
Good idea to not leave it on.? 14 years of solid ON is really extreme and probably a "personal best" for all of us gathered here.EmojiEmoji
______________________________________________________________


On Tuesday, January 9, 2024 at 05:44:17 PM EST, Skip wrote:

... I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.
 

Yes, well no.? Not ON, plugged in!? If nothing else the fan noise would have driven me (more) insane by now!

73's Skip WB6YMH
 

Hi Dean, I would check R3 that goes open a lot. It's a 470K and is near the 120 or 240v fuse holder.

Rick


On 1/8/2024 4:26 AM, HF Radio Solutions wrote:

Hi Bill,

I have an 8920 and the power supply is also dead. A fellow ham said he
could fix it - but that is now 2 years ago. I know nothing about
switchmode power supplies so am not prepared to touch it. I replaced
all caps but had no luck.
I'm in VK5 land. Is there anyone over there that has experience with
switchmode supplies ?

?Regards,

?Dean
?VK5HMV

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