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Discussion in 'Troubleshooting and Repair' started by elektron196, Mar 31, 2013.

  1. elektron196


    Mar 31, 2013
    Hi everyone

    I catch an old LCR Meter with Service Manual
    it shows only "PPPP" in the Display, that means ROM code error U1.
    There is no Support from Agilent anymore.
    Who can help with spare parts or the binary file from this ROM ?
    This Version is the one with only 4 ROM's (U1,3,5,7 ) and 10 for GPIB.
    Sorry for my bad englisch I am from Germany

  2. shrtrnd


    Jan 15, 2010
    You've got the service manual.
    The Error Code is for Check Sum Error, (Component A9U1, which is HP Part Number (ROM) 1818-1134 ).
    The test is for basic isolation of the fault.
    The problem is, this error can also be caused by a problem with HPIB Bus.
    Are you using the HPIB board with other instruments to check the Bus, or is this a
    stand-alone instrument?
    Last edited: Apr 1, 2013
  3. elektron196


    Mar 31, 2013
    Hi shrtrnd

    first, thanks for the fast reply !

    The device is with HPIB Option inside,
    i removed the HPIB board but the error is the same.

    I remove the ROM U1 with a desoldering pump and read it out,
    if somebody have the binary file i try to compare them.

    That's it for the moment

    Have a nice day
  4. shrtrnd


    Jan 15, 2010
    I don't have the file for the ROM.
    Almost half of the HP Test and Measurement instruments I work on were made in
    Did you try to find your U1 ROM?
    I know it's old, but some people still have some of the old HP IC's, and you might
    find somebody with a scrapped 4274A that you can get that chip out of.
  5. shrtrnd


    Jan 15, 2010
    I don't know if you gave up, or are still working this.
    I looked at the circuit. I'd be checking the A7 and A9 boards fiirst.
    I always physically pull the board and look for heat damage first. Sometimes the
    simplest things are the problem.
    I also wanted to say the test that's hanging you up is the initial self-test at turn-on.
    Once you get past this problem, you may still have a problem elsewhere. Don't want
    to dampen your spirits, but wanted you aware of the fact.
    Check page 8-20 of the manual, to run a manual self-diagnosis of the major functions.
  6. elektron196


    Mar 31, 2013
    I wouldn't give up but I need a break, to think about
    all simple things are checked my opinion is ROM bad.
    May be some bits lost, because the device is from 1976.
    Know a Signature Analyzer (HP5004A) would be helpful :)
    I will tell you what's going on.
  7. shrtrnd


    Jan 15, 2010
    It's not unheard of, but the ROM's going bad are unusual.
    If it helps, there are still a lot of 1970's/80's HP gear still up and running.
    They were built to last, and to be repaired when they don't.
    Good luck with the contemplation.
    I'll mention, did you check your power supply voltages to your boards?
    The large electrolytic caps in the power supply going bad/leaking in equipment that old IS
    very common. Wrong Power Supply voltages can do a lot of strange things to the circuits.
    (One more thing to contemplate during your down-time).
  8. SimonsDialogs


    Jun 30, 2019
    It is an old message, but recently I saved the ROM images for the above 4274A ROM, in case you still need it, let me know. I have two units here, in case you want to swap assemblies.
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