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Re: HP8935 Power Supply

 

¿ªÔÆÌåÓý

I¡¯m kicking myself because a couple years ago I sold my parts unit to a friend. ?I¡¯ll have to see whether he still has it or the power supply.

Anyone recall how many 220uf caps it has? Thanks.

KE6CD?

On Nov 14, 2020, at 1:42 PM, MATT SQUIRE <wb9ylp@...> wrote:

?Yup a PITA to get to, just did mine see 8924 thread useful info familiar but not exactly the same layout

Shotgun the Large 220uF @450V caps with good black jacket nichicon105*C and that'll probably nail it. (all I needed)
Check rectifiers & big FET switchers in the area for shorts, too, don't like unpleasant surprises!

Ohm the power rails using correct polarity in case a downstream board/module has a fried rail lytic and isolate (other gear and 856X were notorious)

I also replaced the coin cell 3V cal board basket battery with Energizer Lithium AAA cells because I had a metal holder that'd fit and the 8935'll be phone-sized when my successor will have to 20Y from now
(And I bought AAA instead of AA for the backside battery backup, doofp!)

HP 19.2 KHz video output

 

Does anybody know if there is a published specification for the video output signal on some of the HP equipment that is referred to as the 19.2 KHz signal.I have looked at the signal on a digital scope and a logic analyzer and the Horizontal pulse rate is definitely 19.2 KHz, but I was just wondering if there is a published spec.

Thanks

dave
Re: HP8935 Power Supply

 

Yup a PITA to get to, just did mine see 8924 thread useful info familiar but not exactly the same layout

Shotgun the Large 220uF @450V caps with good black jacket nichicon105*C and that'll probably nail it. (all I needed)
Check rectifiers & big FET switchers in the area for shorts, too, don't like unpleasant surprises!

Ohm the power rails using correct polarity in case a downstream board/module has a fried rail lytic and isolate (other gear and 856X were notorious)

I also replaced the coin cell 3V cal board basket battery with Energizer Lithium AAA cells because I had a metal holder that'd fit and the 8935'll be phone-sized when my successor will have to 20Y from now
(And I bought AAA instead of AA for the backside battery backup, doofp!)
Re: HP8935 Power Supply

 

Hi,
8935 PSU is completely differnt to the 8924C. Like most of this era it may suffer from failed electrolytics. I'm not aware of anything specific though.

Robert G8RPI.
HP8935 Power Supply

 

After sitting idle for a few months and disconnected from AC power, my HP8935 won't power up. It was just fine the last time I used it.

Does anyone know whether its power supply suffers from the same issues as the 8924C in terms of small capacitors that go bad?? I have repaired an 8924C supply in the past but haven't yet dug into the 8935.

Thanks.

KE6CD
Re: Agilent 8935 Cal Constant examples file needed

 

¿ªÔÆÌåÓý

But only applies to parts of the instrument. Specifically, not the spectrum analyser.


On 3 Oct 2020, at 20:59, mstevens53 via groups.io <mstevens53@...> wrote:

?It is in the instrument software, in the Service menus.

Mike Stevens


-----Original Message-----
From: lobos305
Sent: 2020-10-03 10:52:06 AM

Where can I find the Cal procedure?

Re: Agilent 8935 Cal Constant examples file needed

mstevens53
 

It is in the instrument software, in the Service menus.

Mike Stevens


-----Original Message-----
From: lobos305
Sent: 2020-10-03 10:52:06 AM

Where can I find the Cal procedure?
Re: Agilent 8935 Cal Constant examples file needed

 
Edited

Where can I find the Cal procedure?
Re: Agilent 8935 Cal Constant examples file needed

 

My Reference DAC

REF_DAC_COARSE $84
FINE was $9A

YMMV
Re: 8924C PSU failure

 


Thanks, lads!

HP 8935 died

47uF read as 35uF would have started at the wrong end of it

Also replaced the large Chopper caps and board and back panel battery while I was in there...
Used DTV Pilot carrier to dial in freq cal after going crosseyed looking at WWV beat... Dead Nuts now my GPSDO was an 'Epoch Rollover' victim...

73 DE MATT
Agilent 8935 Cal Constant examples file needed

mstevens53
 

Just bought an Agilent 8935 E6380A for Amateur radio and repeater use - test, repair, etc.? It is v0.02.02.
Started with an AA Battery error, fixed.? But now the CR2477 battery is detected as "reading low". Since the Cal status is 0x000C0000, I am certain I need to replace the 3V LI battery, and given the reported Cal info, I'm pretty sure the cal constants are gone.

Keysight/Agilent/HP support databases are not helpful.? I have found most of the normal manuals (user, module-level repair, etc).

So would some kind soul send me a text calibration file so I can at least have a place to start as I make it happy again?

And if you have a working Service PCMCIA card, I am interested in buying it for a fair price.

Mike, N9PP
Added Folder /HP8920 Tools/8924C 8922M cal data G8RPI #file-notice

[email protected] Notification
 

Robert G8RPI added folder /HP8920 Tools/8924C 8922M cal data G8RPI
Re: Program to retrieve HP8920 calibration data...

 

So I downloaded the Cal data from a 8924C and tried to on a 8920B without SA and that halted with an error. I then tried a 8922M opt10 with a SA and that worked OK.
Thanks Jeff.

Robert G8RPI
Re: 8924C PSU failure

 
Edited

Remove all leads
Remove rear feet (two Torx 15 pet foot)
Remove strap handles (two phillips per strap)
Remove M3 screws under strap (lots of Torx 10)
Pull bottom edges of cover out sightly, slide back a bit and lift off.
Internal covers have instructions on them.
The repair manual is in Files.

Opps,
Forgot 4 T15 screws holding cover to rear panel.
Robert G8RPI.
Re: 8924C PSU failure

 

Does someone have the disassembly proceedure for opening the case?
Re: 8924C PSU failure

 

usually its just the one cap on the +15 volt standby supply which is on the daughter card.

No green LED when plugged in which I think that document goes through.

the standby supply is obviously on whenever the unit is plugged in so more prone to the capacitors aging.

Usually do not do the 8924 main board caps unless they failed.

8920a/b 8921's have the main caps fail more often on the low voltage outputs
Re: 8924C PSU failure

 

Couldn¡¯t agree more! Replace all the electrolytic capacitors in the supply.?
Re: 8924C PSU failure

 

Thankfully I was able to move just about all the files and pictures from the old group to here.

Photos: 26 MB
Files: 131 MB

Including the famous guide to repairing your 8924 power supply.



Take a look? at the files and photos if you haven't already.

Hank
Re: 8924C PSU failure

 

Thanks for the tip, Ralph.

I actually had an old PDF from an unknown source, probably the old Yahoo groups, that I had kept. Gives details of what appears to be the same cap you described.
47uF 50V. The one in mine read 41uF. A new one cured it.

The author of the PDF is unknown and interesting it had gone from the WWW.
I make a habit of keeping local copies of this sort of data. You can never be sure if it will be on the web when you need it. These are the new dark ages.

Robert G8RPI
Re: 8924C PSU failure

 

I would replace all the electrolytics.
The hard part is getting to them.
Unless you just like removing all those screws.
They are all the same age and once they start failing, they fall like dominoes.

Sorta like fixing a car engine, you do not just replace the rings on the cylinder with low compression.
You replace them all.

73
Glenn
WB4UIV
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