[time-nuts] HP 3458A ISOLATOR DTACK err @ pwr up

Ed Palmer ed_palmer at sasktel.net
Wed Jul 29 23:45:18 UTC 2009


Hi Brooke,

Three thoughts:

1.  If CR11 or CR12 blew open, the LM317 and LM337 might have been 
damaged.  Are your +18 & -18 supplies okay?  By the way, I think you've 
got them reversed on the schematic.  The LM317 should be connected to 
CR01 and CR02.

2.  On the web page you mentioned that CR10 survived.  Does that mean 
that CR09 blew open?  If so, did your +5 take a hit?  That could be the 
cause of all your problems.

3.  If it was strapped for 110 and plugged into 220, how much current 
would the transformer itself draw due to the overvoltage?  Would that 
pop the fuse all by itself?  I've never tried such a thing ( and have no 
intentions of trying it!).

Ed

Brooke Clarke wrote:
> Hi:
>
> I've traced enough of the circuit to know the Zener diodes that blew 
> act as input protection for the A4 power supply.  This unit had a 
> sticker saying "Strapped for 220 VAC" when I received it.  I changed 
> it to 120 VAC.
>
> BUT, if the prior owner plugged it into 220 VAC while it was strapped 
> for 120 VAC this is exactly what you would expect to happen.  For 
> partial board layout and partial schematic see:
> http://www.prc68.com/I/HP3458DVM.shtml#A4
>
> Note that the line fuse for 220 VAC is 0.5 Amp and for 120 VAC is 1.5 
> Amp.  The Zener diodes are rated for 5 Watts so a drop of 40 volts can 
> only support 125 ma. and the line fuse would be 1.5 Amp so offers no 
> protection.  Best to put a fuse at the input to the board as a way to 
> protect A4 from this mistake.
>
> Could probably run it without the Zener diodes, but will replace them 
> prior to powering it up.
>
> Have Fun,
>
> Brooke Clarke
> http://www.prc68.com
>
> Brooke Clarke wrote:
>> Hi:
>>
>> I've started a web page for the HP 3458A and it's problem with more 
>> info at:
>> http://www.prc68.com/I/HP3458DVM.shtml
>>
>> Have Fun,
>>
>> Brooke Clarke
>> http://www.prc68.com
>>
>> Brooke Clarke wrote:
>>> Hi Greg:
>>>
>>> I tried both Blue then Error and Blue and Error and could not get 
>>> anything, i.e. the display just showed ISOLATOR DTACK
>>>
>>> Have Fun,
>>>
>>> Brooke Clarke
>>> http://www.prc68.com
>>>
>>> Greg Burnett wrote:
>>>> Brooke:
>>>>
>>>> ...Correction to my last post... If I remember correctly, you would 
>>>> hit "key shift blue" + "Clear" to clear out each error message in 
>>>> order to read the next error message (if any). You keep clearing 
>>>> the error messages until there are none left. Be sure to use the 
>>>> left & right arrows to scroll through a given error message's 
>>>> complete text line.
>>>>
>>>> Poul-Henning's suggestion (about the optical cables on the bottom 
>>>> side) is worth trying. If I remember correctly, the box will still 
>>>> function (except for Ext. Trigger Input and VM Complete Output) if 
>>>> the rear optical cables are disconnected. However you will get an 
>>>> isolator error if the front optical cables are disconnected. But 
>>>> I'm not sure if it will be your error 201 or 200 (Isolator does not 
>>>> respond).
>>>>
>>>> Let us know what you find.
>>>>
>>>> Greg
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at febo.com
>>>> To unsubscribe, go to 
>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at febo.com
>>> To unsubscribe, go to 
>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>




More information about the Time-nuts_lists.febo.com mailing list