hp 6267b power supply problem need help

Discussion in 'General Electronics Chat' started by pastinsain, Jul 12, 2016.

  1. pastinsain

    Thread Starter Member

    Aug 25, 2012
    160
    2
    problem ,... the power supply volts needle gage is very slow returning to 0 volt after turning off.
    I think part of the problem is that i had two supplies connected in series with diodes and one of the diodes fell off the output terminals. Thats when I noticed
    the slow return to 0 volts of the volt meter. When I set the volts to like 35v and then turn off supply, the needle will take a long time 3 min to return to 0 volts
    In addition, after turning off supply the ne
     
  2. pastinsain

    Thread Starter Member

    Aug 25, 2012
    160
    2
    I'm sorry I didn't finish the power supply problem.
    problem...2 when I turn off the supply, the volts needle gage will drift upward from about 3 volts to 10 volts then takes a long time to settle back to 0 volts.
    What happen the the circuit when the protection diode fell off when I had it connected in series with another power supply?
     
  3. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    Have a look whether the BAMA boat anchor website is still going - I got the schematics for an old HP RF signal generator there.

    Mine had a 200V minus rail regulated by a 180V glow tube to stabilise the positive rail cathode follower.

    On mine; the glow tube had gone OC, too much negative voltage in the regulation circuit translated into low voltage on the positive rail.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
  5. pastinsain

    Thread Starter Member

    Aug 25, 2012
    160
    2
    thank you , I will try that, however , the back volts/ current from the other supply connected in series protection diode falling off did something to the circuit .
     
  6. pastinsain

    Thread Starter Member

    Aug 25, 2012
    160
    2
    I found this in the hp file at boat anchor ...
    ""3-68 Active loads connected to the power supply
    may actually deliver a reverse current to the power
    supply during a portion of its operating cycle. An
    external source cannot be allowed to pump current
    into the supply without loss of regulation and pos-
    sible damage to the output capacitor. To avoid
    these effects, it is necessary to preload the supply
    with a dummy load resistor so that the power supply
    delivers current through the entire operation cycle
    of the load device"" .. end quote ... I may have damaged the output cap when the diode fell off during the series connection!
     
  7. pastinsain

    Thread Starter Member

    Aug 25, 2012
    160
    2
    in addition I failed to put a dummy load across output . looks like I may start with the output cap. Also I need to mention , when I put a dummy load 16ohm resister on the output, the power supply works ok then and needle returns to 0 volts with no problem . Its only happens when the output has no load .
     
    Last edited: Jul 12, 2016
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