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hp 83522a 2.4 ghz rf plug for 8350b
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gleamfollower
--- In hp_agilent_equipment@..., "inert12001"
<inertial@j...> wrote: I'm having a problem with the sampler board. I have service manualafter the schotky diode which checks ok on my DVM. Anyone have anyNot usually a good idea to check these diodes with ohmmeters or (especially) DVM diode-test functions. You may have blown the diode. :( |
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John Miles
开云体育Couple
of ways:
?
1) See
how well it acts as a mixer in the frequency range in question.? (This is
what I usually test, since the DUT is usually part of a?mixer
assembly.)
2) Use
a curve tracer with appropriate current limits.
3)
Look up the diode's maximum forward current limit and make sure that your VOM
doesn't exceed it.? Possibly need to disable autoranging on the meter to
make sure.?
?
--
jm
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I do not think that it is current that would kill schottky diode, it is
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reverse voltage that might do it in. Some of very old meters were putting 100 mA on low ohm range, but I do not think that there are any of those left functional. Most digital meters use 1 mA current source and then measure voltage. I understand that some of those DVMs have output voltage that reaches level of its supply buttery and that is where you can damage a schottky. Oops, I went to check my Fluke and that is one of those 'schottky diode damaging meters' that applies 8 V plus to output terminals at no load; I was under impression that Fluke used a voltage clamp for all Ohm ranges, but, I guess, I was fooled. It is funny that my 'Harbor Freight Special', $3.99 meter is using 0.85 mA and output voltage does not exceed 2.6 V, what would be satisfactory for schottky diodes used in sampling bridges. Regards Miroslav Pokorni ----- Original Message -----
From: "John Miles" <jmiles@...> To: <hp_agilent_equipment@...> Sent: Friday, September 05, 2003 7:56 AM Subject: RE: [hp_agilent_equipment] Re: hp 83522a 2.4 ghz rf plug for 8350b Couple of ways:your VOM doesn't exceed it. Possibly need to disable autoranging on the meterto make sure. |
开云体育jm
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I checked the manual on my protek 506 dvm & it
said that the test current for diode testing is 1 ma.? The diode in
question is acting as a switch which is controlled by a bias voltage based on
frequency which is controlled by a MUX24FQ 4 channel analog ic.? If the mux
has failed then the bias will not be correct.? When I meter the circuit in
question I get -.34 v. relative to ground which would keep the diode off.?
In any event I just tested the main osc. on the unit and it has stopped working
& I had it up & running last week after resoldering the osc. control
board.? Frustrating.
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Thanks
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Richard
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开云体育Thanks for the helpful suggestions,? I will
check the voltage potential on my DVM.
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Regards
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Richard Murray |
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