AnsweredAssumed Answered

Please suggest repairs for my 70900A or 70908A.

Question asked by UptonOGood on Nov 7, 2010
Latest reply on Nov 11, 2010 by JohnMiles
I sure would appreciate any suggestions for fixing my 70000 system.  I think the problem is in the RF Module but I'm not sure. Below I've written out all the details.  I know its a lot to read but hopefully someone will be kind enough to offer their knowledge.  This system was working perfectly one day, and suddenly stopped the next. I'm not a rich company so I have to fix this myself.  It happened on a really hot day. So it could be that a part just fried.  It could also be that the RF input was over-driven with too much power, maybe. Thanks guys.  --Upton

70000 System has the following modules:     

          70310A     Precision Frequency Reference
          70902A     IF Section
          70903A     IF Section
          70900A     LO Module
          70908A     RF Module
          70907A     External Mixer Interface Module

PROBLEM DESCRIPTION

1) There are error codes which change from one power-up to another, see below.

2) Input has been given a variety of input signals but none of them show up on the display. Display shows a noise floor (sometimes) but will not display any signals.

3) On startup the frequency range is 18-26 GHz, and a noise floor is seen from 18-26 GHz.  As the frequency range is adjusted, the noise floor is not always shown across the whole band.  Example, display might show <-120 db from DC-2.5 GHz (trace is out of range), then there is a step up to -70 db from 2.5-5 GHz. The freq of this step-up (or step-down) changes depending on the start and stop freqs, and seems to make no logical sense.

4) The 70908A RF Module breifly flashes its two LED's on startup, but both stay dark thereafter.  I would expect at least the green "active" LED to stay on. 

ERROR MESSAGES:

I get anywhere from zero to three error messages.  Sometimes there are NO error messages, but all the symptoms above remain.  Here is the full list of messages I got today:
*          YTO IS UNLOCKED.           ERR 7016.  70900B
*          OVEN COLD.                     ERR 6015.  70310A (Goes away when warm, only listed here for completeness.)
*          HARDWARE CONFIG FAIL.  ERR 7050.  70900B (Note I actually have a version A, not B)

EFFORTS MADE:

1) Since 2 errors point to the 70900 LO Module, I pulled it out and placed it into a known-good working system.  It worked perfectly, no errors, no problems. I condlude my 70900A is fine.

2) Since the 70900 version was not detected (says B not A), and that start-up test uses the two fat multi-pin harness cables, I replaced them for known-good ones. Made no difference.

3) I cleaned and re-seated all modules and connectors.  I inspected all the rear interconnects, and verified the rear configuration with the manual.

QUESTIONS:

1) Can I conclude the problem is with the RF Module? 

2) Based on these symptoms, does anyone know what the repair is likely to involve? 

3) To do this myself, will I need to be able to power-up the module outside the mainframe?  I do not have any special extention cables or open frames which I suspect service guys use.

4) Is there a "most likely" fix which I can perform even without the ability to test inside with a powered open frame, to see if it works?

5) If I cant do this myself, can anyone recommend someone who can?

Wow you made it all the way through my post, thanks a million!  Cheers.

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