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HP8568B does not start.

 

Hi All,

I was given a HP8568B that doesn't work.

The 85662 display section is good but it seems the CPU in the analyzer box does not boot. The lithium battery on A15 leaked and was removed at some stage in the past. The acid got under the clock module and ate the leads away. The rest of the board looks ok so I pulled the clock chip and substituted an external 14.7456MHz oscillator for the purpose of testing but still nothing from the CPU.?

All power supplies measure good. Both INSTR CHECK LEDs remain on. None of the LEDs on A15 come on ever even if I push the INSTRUMENT PRESET key. All the yellow leds on both units remain illuminated.

I don't have extender cards, just a 'scope and a meter. However I do have another functional 8568B.

Is it reasonable to take a good A15 card from one machine and put it in another for troubleshooting purposes? Besides the terrifying risk that I might end up with two dead analyzers is there anything else I should consider??

Regards

Lou
VK3ALB
 

Lou -
Possibly - I'm more familiar with the 8566. Many times the number of the CPU board was changed because of chip substitution with no external function change.

Here are things to check:
1) Are the first 4 digits of the SN the same
2) Are the motherboard part numbers the same
3) Are the CPU numbers the same
4) Are the FIRMWARE versions the same

If 2,2 and 4 are identical, absolutely OK to change. If 2 and 4 are the same but 3 is different, probably OK - go to Keysight find a part site, put in the part number of the EXISTING CPU and see if the WORKING CPU is a substitute = OK.
If 4 are the same it is also probably OK

Just collect all the data B4 doing the sub.

Cheers!

Bruce


Quoting Lou Blasco <vk3alb@...>:

Hi All,

I was given a HP8568B that doesn't work.

The 85662 display section is good but it seems the CPU in the analyzer box
does not boot. The lithium battery on A15 leaked and was removed at some
stage in the past. The acid got under the clock module and ate the leads
away. The rest of the board looks ok so I pulled the clock chip and
substituted an external 14.7456MHz oscillator for the purpose of testing
but still nothing from the CPU.

All power supplies measure good. Both INSTR CHECK LEDs remain on. None of
the LEDs on A15 come on ever even if I push the INSTRUMENT PRESET key. All
the yellow leds on both units remain illuminated.

I don't have extender cards, just a 'scope and a meter. However I do have
another functional 8568B.

Is it reasonable to take a good A15 card from one machine and put it in
another for troubleshooting purposes? Besides the terrifying risk that I
might end up with two dead analyzers is there anything else I should
consider?

Regards

Lou
VK3ALB
 

Does your 8568B have the internal 10MHz OCXO running? If not check the internal/external ref switch for the correct setting. If set to internal, check for 10 MHz at about -10 dBm at the rear 10 MHz port. If missing, put 10MHz at greater than -10 dBm into the ext ref port.
The 8568 will not run - giving some of the symptoms you listed. The internal system RF chain and a chunk of the digital electronics will not function without the 10 MHz. This is unlike the 8566 which runs off the internal 100MHz (locked to the 10 MHz).
Don Bitters
 

Hi Bruce,

Thank you for your reply. The CPU boards were identical and swapping them confirmed the dead 8568B chassis was indeed fully functional. I'll keep working on the A15 and perhaps I might find what's wrong with it.

@Don Bitters - Thanks for your suggestion but this test confirms that the internal 10MHz reference is functional.

Regards

Lou
VK3ALB


On Sat, Feb 19, 2022 at 5:46 PM Bruce <bruce@...> wrote:
Lou -
Possibly - I'm more familiar with the 8566.? Many times the number of?
the CPU board was changed because of chip substitution with no?
external function change.

Here are things to check:
1) Are the first 4 digits of the SN the same
2) Are the motherboard part numbers the same
3) Are the CPU numbers the same
4) Are the FIRMWARE versions the same

If 2,2 and 4 are identical, absolutely OK to change.? If 2 and 4 are?
the same but 3 is different, probably OK - go to Keysight find a part?
site, put in the part number of the EXISTING CPU and see if the?
WORKING CPU is a substitute = OK.
If 4 are the same it is also probably OK

Just collect all the data B4 doing the sub.

Cheers!

Bruce


Quoting Lou Blasco <vk3alb@...>:

> Hi All,
>
> I was given a HP8568B that doesn't work.
>
> The 85662 display section is good but it seems the CPU in the analyzer box
> does not boot. The lithium battery on A15 leaked and was removed at some
> stage in the past. The acid got under the clock module and ate the leads
> away. The rest of the board looks ok so I pulled the clock chip and
> substituted an external 14.7456MHz oscillator for the purpose of testing
> but still nothing from the CPU.
>
> All power supplies measure good. Both INSTR CHECK LEDs remain on. None of
> the LEDs on A15 come on ever even if I push the INSTRUMENT PRESET key. All
> the yellow leds on both units remain illuminated.
>
> I don't have extender cards, just a 'scope and a meter. However I do have
> another functional 8568B.
>
> Is it reasonable to take a good A15 card from one machine and put it in
> another for troubleshooting purposes? Besides the terrifying risk that I
> might end up with two dead analyzers is there anything else I should
> consider?
>
> Regards
>
> Lou
> VK3ALB
>
>
>








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