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Some HP 8341A questions


 

开云体育

Hi,
I got a HP 8341A for free! however, there is a little problem:
The A55 board is faulty (YO driver), as well as the YTO. The rest of the device should be fine. The YO and A55 are faulty because the unit was used for parts to repair another unit.
I wonder what the chances are to repair the 8341A. I know only these two assemblies should be faulty; I guess, a YO could be found on ebay (no luck today, though) but I don't know whether it is possible to fix A55.
I found a service manual here



but no schematics there. Has anyone some experience with the 8341A?

And some other question: My unit has the RF output on the rear panel; I wonder whether it is possible with affordable effort to install the RF output on the front panel?

Thanks for any hints,
best
Tobias, HB9FSX


 

开云体育

Hi all,
in case anyone can help:
today I opened my 8341A and I found out that the YIG used is a HP 5086-7323, just in case anyone has a replacement ;-) Is it possible to test that YIG somehow outside the instrument?
I know that the A55 board, the YO driver, HP PN 08340-60202, is also faulty. So, with a bit of luck, the YIG may still be ok and if I exchange A55 everything is fine. However, if possible, I would like to verify whether the YIG oscillates.
Does this make sense?

Tobias



From: hp_agilent_equipment@... [hp_agilent_equipment@...]
Sent: Tuesday, October 03, 2017 16:50
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Some HP 8341A questions

?

Hi,
I got a HP 8341A for free! however, there is a little problem:
The A55 board is faulty (YO driver), as well as the YTO. The rest of the device should be fine. The YO and A55 are faulty because the unit was used for parts to repair another unit.
I wonder what the chances are to repair the 8341A. I know only these two assemblies should be faulty; I guess, a YO could be found on ebay (no luck today, though) but I don't know whether it is possible to fix A55.
I found a service manual here



but no schematics there. Has anyone some experience with the 8341A?

And some other question: My unit has the RF output on the rear panel; I wonder whether it is possible with affordable effort to install the RF output on the front panel?

Thanks for any hints,
best
Tobias, HB9FSX


Tom Miller
 

开云体育

It is possible to run the YIG by itself. Do you have a spectrum analyzer to look at the output?
?
You will need several power supplies. Probably two to power the oscillator and a constant current supply to power the coil.
?
If you can take a few good pictures of the board, we may be able to make a few more suggestions.
?
Do you have a schematic for the 8341A?
?
?
Regards
?
?

----- Original Message -----
Sent: Wednesday, October 04, 2017 11:03 AM
Subject: [hp_agilent_equipment] RE: Some HP 8341A questions

?

Hi all,
in case anyone can help:
today I opened my 8341A and I found out that the YIG used is a HP 5086-7323, just in case anyone has a replacement ;-) Is it possible to test that YIG somehow outside the instrument?
I know that the A55 board, the YO driver, HP PN 08340-60202, is also faulty. So, with a bit of luck, the YIG may still be ok and if I exchange A55 everything is fine. However, if possible, I would like to verify whether the YIG oscillates.
Does this make sense?

Tobias



From: hp_agilent_equipment@... [hp_agilent_equipment@...]
Sent: Tuesday, October 03, 2017 16:50
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Some HP 8341A questions

?

Hi,
I got a HP 8341A for free! however, there is a little problem:
The A55 board is faulty (YO driver), as well as the YTO. The rest of the device should be fine. The YO and A55 are faulty because the unit was used for parts to repair another unit.
I wonder what the chances are to repair the 8341A. I know only these two assemblies should be faulty; I guess, a YO could be found on ebay (no luck today, though) but I don't know whether it is possible to fix A55.
I found a service manual here



but no schematics there. Has anyone some experience with the 8341A?

And some other question: My unit has the RF output on the rear panel; I wonder whether it is possible with affordable effort to install the RF output on the front panel?

Thanks for any hints,
best
Tobias, HB9FSX


 

Don't power directly the yig. The schematics diagrams of the8341A gives the various supplies to the connector on the yig board Be very careful with the negative supply biasing a FET very static sensitive.
--------------------------------------------

On Wed, 10/4/17, 'Tom Miller' tmiller11147@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:

Subject: Re: [hp_agilent_equipment] RE: Some HP 8341A questions
To: hp_agilent_equipment@...
Date: Wednesday, October 4, 2017, 6:06 PM


?












It is possible to run
the YIG by itself. Do you
have a spectrum analyzer to look at the output?
?
You will need several power
supplies. Probably two
to power the oscillator and a constant current supply to
power the
coil.
?
If you can take a few good
pictures of the board,
we may be able to make a few more suggestions.
?
Do you have a schematic for
the 8341A?
?
?
Regards
?
?

----- Original Message -----

From:
Tobias Pluess
tobias.pluess@... [hp_agilent_equipment]
To: hp_agilent_equipment@...


Sent: Wednesday,
October 04, 2017 11:03
AM
Subject:
[hp_agilent_equipment] RE: Some
HP 8341A questions

?


Hi

all,
in case anyone can help:
today I opened my 8341A and I found out
that the YIG used is a HP 5086-7323, just in case anyone
has a replacement ;-)
Is it possible to test that YIG somehow outside the
instrument?
I know that
the A55 board, the YO driver, HP PN 08340-60202, is also
faulty. So, with a
bit of luck, the YIG may still be ok and if I exchange A55
everything is fine.
However, if possible, I would like to verify whether the
YIG
oscillates.
Does this make sense?

Tobias






From:
hp_agilent_equipment@...
[hp_agilent_equipment@...]
Sent: Tuesday, October 03,
2017 16:50
To:
hp_agilent_equipment@...
Subject: [hp_agilent_equipment]
Some HP 8341A questions



?




Hi,
I
got a HP 8341A for free! however, there is a little
problem:
The A55 board
is faulty (YO driver), as well as the YTO. The rest of the
device should be
fine. The YO and A55 are faulty because the unit was used
for parts to repair
another unit.
I wonder what the chances
are to repair the 8341A. I know
only these two assemblies should be faulty; I guess, a YO
could be found on
ebay (no luck today, though) but I don't know whether
it is possible to fix
A55.
I found a service manual here



but
no schematics there. Has anyone some experience with the
8341A?

And
some other question: My unit has the RF output on the rear
panel; I wonder
whether it is possible with affordable effort to install
the RF output on the
front panel?

Thanks for
any hints,
best
Tobias,
HB9FSX















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Yes, it is possible to test the YTO out of the box. It usually needs +15V, -5V. Heater is not necessary for it to oscillator.

Be very careful about the FM coil. I would just tune the main coil only. You need an SA to watch the output. It's usually at +10dBm.

Regards,
Calvin


 

开云体育

Hi,

today I have dismantled the YO loop assembly, which contains the YTO as well as severak directional couplers etc., see here, this is my unit:



The YTO is the following one



and the PCB can be seen more clearly in this pic:



Does somebody have experience with these HP YTOs? I will test it today, but probably someone has some experience and can give a few hints.

I see a testpoint with +5, I assume this is +5V supply. There are two further testpoints for +20V and -40V. I wonder whether I need all these voltages, or just a few?

Best
Tobias


From: hp_agilent_equipment@... [hp_agilent_equipment@...]
Sent: Wednesday, October 04, 2017 23:28
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: Some HP 8341A questions

?

Yes, it is possible to test the YTO out of the box. It usually needs +15V, -5V. Heater is not necessary for it to oscillator.


Be very careful about the FM coil. I would just tune the main coil only. You need an SA to watch the output. It's usually at +10dBm.

Regards,
Calvin


 

开云体育

Hi,

I was able to remove theYTO from the instrument and test it with the aid of a spectrum analyzer and a few power supplies. Mine needs +20V, -10V, and +5V.



With a coil current of approx. 50mA, I was able to see some oscillation on the spectrum analyzer. YAY!

However, as soon as I installed the YTO back in the instrument, it stopped working.
I found out why: The Main Coil, pin 9, has a connection to ground. As one can see, if pin 9 on the A44 YIG OSC Assembly has a connection to ground, this creates a short circuit and -40V are applied to the main coil. Then, the tuning current is so incredibly high that the YTO won't oscillate.

As soon as I remove the YTO from the instrument, it works fine because with my lab power supplies I have no ground connuection and therefore can properly apply the tuning current.

I wonder now whether it could theoretically be possible, somehow, to open the YTO, find the short circuit and place some isolation tape or so. Has anybody ever done something like that? the YTO microcircuit is definitely fine and oscillates, as it should, but the main coil is somehow connected to the housing, which, according to the schematics, should not be the case I think.


Any ideas?

Best
Tobias



From: hp_agilent_equipment@... [hp_agilent_equipment@...]
Sent: Wednesday, October 04, 2017 23:28
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: Some HP 8341A questions

?

Yes, it is possible to test the YTO out of the box. It usually needs +15V, -5V. Heater is not necessary for it to oscillator.


Be very careful about the FM coil. I would just tune the main coil only. You need an SA to watch the output. It's usually at +10dBm.

Regards,
Calvin


 

In a typical HP YTO loop config, one end of the main coil is connected to -40V, the other is connected to the emitter of the main coil driver. The current through the main coil is controlled by the drive transistor. Look closer to your driver board.?

The main coil has absolutely no chance of surviving a 40V DC. Do you have? schematics of the YTO loop?

Good luck,
Calvin