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HP 71200C (HP 70600a) Input attenuator problem

Question asked by n8phu on Jul 17, 2008
Latest reply on Jul 24, 2008 by hp35665a

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All,

   I finally got he power supply repaired in the HP 70001A frame. I ran the system diagnostics and it quit the test with a ERR 60 RF Attenuator fault. I opened the HP 70600A module, found the programmable attenuator ( I will look up the part number when I get home).

   I took the attenuator out of the module and looked at it. I took the case off of it and found the mechanical switches that switch the attenuators in and out. One of them seems to be binding up a little. I was wondering if I lubricate the switch would it fix the problem.

My question is, what is reccommended as a lube? Light machine oil, sewing machine oil, Graphite?????

Any ideas would be appreciated.

Chris N8PHU

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n8phu Jul 17, 2008 10:36 AM

I also found out that I have a 71200C Spec An, not a 71210C.

Chris N8PHU

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n8phu Jul 17, 2008 10:02 PM

Well, now I went and did it... I fixed the input attenuator. I had taken the 70600A module apart to get the part number off of it. I removed the attenuator module from the 70600A and taken the "C" shell off of it. I was looking at the innards of the unit when I bumped a small screwdriver and it attached to the steel covering over the last attenuator in line. I tried to move the screwdriver, but it wouldn't come off easy....

The steel covering over the attenuator had magnetized! What \would happen is the attenuator would switch in line, but the motor didn't have enough "Ooomph" to move it out of line due to the magnetized parts.

So off to do some research to de magnetize them... hmm, heat is the preferred method. So out came the soldering iron capable of 450 degree Celsius.....

I heated the steel covering and the plunger... being careful not to singe the board or my fingers...

It's working now! Had the unit run the internal diagnostics and cal routine. All pass!

One working HP 71200C model Spec An ready for duty....

Chris N8PHU

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hp35665a Jul 24, 2008 7:46 PM

I am looking at buying one of these preselectors and a 70905a rf section at the moment.

Do you know the attenuation range of the 70600a? I can't seem to find a manual for it.

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n8phu Jul 17, 2008 10:36 AM
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Correct Answer
I also found out that I have a 71200C Spec An, not a 71210C.

Chris N8PHU
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n8phu Jul 17, 2008 10:02 PM
Mark Correct
Correct Answer
Well, now I went and did it... I fixed the input attenuator. I had taken the 70600A module apart to get the part number off of it. I removed the attenuator module from the 70600A and taken the "C" shell off of it. I was looking at the innards of the unit when I bumped a small screwdriver and it attached to the steel covering over the last attenuator in line. I tried to move the screwdriver, but it wouldn't come off easy....

The steel covering over the attenuator had magnetized! What \would happen is the attenuator would switch in line, but the motor didn't have enough "Ooomph" to move it out of line due to the magnetized parts.

So off to do some research to de magnetize them... hmm, heat is the preferred method. So out came the soldering iron capable of 450 degree Celsius.....

I heated the steel covering and the plunger... being careful not to singe the board or my fingers...

It's working now! Had the unit run the internal diagnostics and cal routine. All pass!

One working HP 71200C model Spec An ready for duty....

Chris N8PHU
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hp35665a Jul 24, 2008 7:46 PM
Mark Correct
Correct Answer
I am looking at buying one of these preselectors and a 70905a rf section at the moment.

Do you know the attenuation range of the 70600a? I can't seem to find a manual for it.
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HP 71200C (HP 70600a) Input attenuator problem

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