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Science Forum Index » Electronics - Equipment Forum » Defective Power supply in HP8711a Network Analyser.
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| Max65 |
 Posted: Sun Mar 09, 2008 10:36 pm |
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Hi Caesar, nice to meet you again here, hope you are good.
The wheather here is still very cold, and the flu is just around the
corner. In Santa Rosa it should be better I guess, you are very lucky
to live in Californian climate.
Ivo is very worried about his 8711, so I suggested him to ask you
about it.
Ivo.
I'm not sure where I found out it, but somewhere (this is for sure),
there is a service note about the 8711 that explain some mods made to
the PSU, one was about a power resistor (about one watt, I guess)
added on the solder side near the backplane connector socket. Even if
i remember well, it was added to avoid the PSU lockup when the 8711
power switch was left on and the power was switched outside the
instrument.
Does your 8711 PSU have that resistor soldered on the solder side?
Massimo |
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| Rivendel_Ivo |
| Posted: Mon Mar 10, 2008 5:48 am |
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Hello Massimo.
No modifications on my 8711; the instrument is in a "virgin"
state.....
Very curious about the modifications, of course! I cannot find
anything on the web though.
Weather state over here is typical Dutch March weather; cloudy with
rain;
strong winds 5 BF here near the German border and 9 degrees C over
daytime...
(PS: I was on my bike towards my work this morning....)
Were do you live?
Ivo. |
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| Max65 |
| Posted: Mon Mar 10, 2008 6:59 am |
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Ok Ivo,
I don't remember where I found the mods, I'm sure on the web.
Now I go home, and I search for them in my home workshop. I should had
printed them on paper and put them somewhere (my workshop is not what
you can say "a well-kept environment").
I live in a small town few km from the Malpensa International Airport
of Milan. Here is very cold and rainy today. I hope the spring came
soon.
Massimo |
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| Max65 |
| Posted: Mon Mar 10, 2008 10:43 am |
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Hi Ivo,
I was wrong. The mods was to avoid the intermittent memory loss on the
HP8711A with SN from 0000A00000 to 3325A00941.
If your instrument has the SN between the above limits you should have
one 680ohms / 3Watts resistor soldered under the PSU. The resistor
must be connected to pin 9 and pin 16 of the PSU connector J5.
Hope this can help you, even if it seems to be another issue.
Have a nice day.
Massimo |
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| Rivendel_Ivo |
| Posted: Mon Mar 10, 2008 7:53 pm |
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On Mar 10, 9:43 pm, Max65 <mpor...@tele2.it> wrote:
Quote: Hi Ivo,
I was wrong. The mods was to avoid the intermittent memory loss on the
HP8711A with SN from 0000A00000 to 3325A00941.
If your instrument has the SN between the above limits you should have
one 680ohms / 3Watts resistor soldered under the PSU. The resistor
must be connected to pin 9 and pin 16 of the PSU connector J5.
Hope this can help you, even if it seems to be another issue.
Have a nice day.
Massimo
In the mean time, just got schematics from Ceasar by mail!!
I will try to find the ghost in the SMPS box....I will let you know! |
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| Max65 |
| Posted: Mon Mar 10, 2008 10:44 pm |
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Quote: In the mean time, just got schematics from Ceasar by mail!!
I will try to find the ghost in the SMPS box....I will let you
know!
Great!
Ceasar is a great guy.
Let me know,
when you fix it, I can give you the mods to convert it to a full
loaded 8712 for free.
(If you want I can give you now, but it's better you fix it before).
Massimo |
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| Rivendel_Ivo |
| Posted: Wed Mar 26, 2008 11:20 am |
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On Mar 11, 9:44 am, Max65 <mpor...@tele2.it> wrote:
Quote: In the mean time, just got schematics from Ceasar by mail!!
I will try to find the ghost in the SMPS box....I will let you
know!
Great!
Ceasar is a great guy.
Let me know,
when you fix it, I can give you the mods to convert it to a full
loaded 8712 for free.
(If you want I can give you now, but it's better you fix it before).
Massimo
With the schematics by hand, it was not very difficult to pinpoint the
problem.
The SMPS of the 8711 is equipped with Under and Over-voltage lockout
circuitry; this is situated on a sub-PCB in the supply itself. This
OVL and UVL circuits are based on a common LM139 comparitor; this one
shows extreme bias on the inputs so treshold levels are wrong.
The simplest thing to do (IC exchange was difficult to realize) was a
complete disabling of the UVL and OVL circuit.
The supply works well and the analyzer is operational!
Thanks for the help !!!
Ivo. |
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| Caesar Valenti |
| Posted: Thu Mar 27, 2008 2:44 am |
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Guest
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Rivendel_Ivo wrote:
Quote: On Mar 11, 9:44 am, Max65 <mpor...@tele2.it> wrote:
In the mean time, just got schematics from Ceasar by mail!!
I will try to find the ghost in the SMPS box....I will let you
know!
Great!
Ceasar is a great guy.
Let me know,
when you fix it, I can give you the mods to convert it to a full
loaded 8712 for free.
(If you want I can give you now, but it's better you fix it before).
Massimo
With the schematics by hand, it was not very difficult to pinpoint the
problem.
The SMPS of the 8711 is equipped with Under and Over-voltage lockout
circuitry; this is situated on a sub-PCB in the supply itself. This
OVL and UVL circuits are based on a common LM139 comparitor; this one
shows extreme bias on the inputs so treshold levels are wrong.
The simplest thing to do (IC exchange was difficult to realize) was a
complete disabling of the UVL and OVL circuit.
The supply works well and the analyzer is operational!
Thanks for the help !!!
Ivo.
Glad you got it working.....it's nice to know that the schematics helped.
CV |
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