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

Brooke Clarke brooke at pacific.net
Thu Jul 30 21:08:28 UTC 2009


Hi Ed:

Yes, all the supply voltages are within spec, but the error message stays the same.

The Outguard supply visually looks OK and the voltages are centered in the spec.

Yes the transformer has seven wires feeding the outguard p.s.

See: http://www.prc68.com/I/HP3458DVM.shtml#Bot
You may need to <shift><reload page> to see it.

Have Fun,

Brooke Clarke
http://www.prc68.com

Ed Palmer wrote:
> You're right.  Sorry.
> 
> Brooke, now that you know the source of at least this problem, have you 
> considered powering up the system by applying DC to the inputs of the 
> regulators?  This would allow you to limit the current in case there's 
> been some damage further in.
> 
> Also, is the Outguard p.s. connected to the same transformer?  I would 
> expect to see a similar circuit topology on both supplies.  Is there any 
> heat damage on the Outguard p.s.?
> 
> Ed
> 
> J. Forster wrote:
>> Look at the Ohms readings. It's not open, if the readings are right.
>>
>> -John
>>
>> =============
>>
>>
>>  
>>> Try putting a light load on the transformer when you measure the output
>>> voltage (maybe 1K).  You may find that terminals 2-3 are open circuit
>>> rather than short.  Maybe that's why CR10 survived - the transformer
>>> blew first.
>>>
>>> Ed
>>>
>>> Brooke Clarke wrote:
>>>    
>>>> Hi John:
>>>>
>>>> It's hard to say.  With the A4 Inguard p.s. board removed when powered
>>>> up the fan comes on and the display lights up with the error message.
>>>>
>>>> So, measured on the primary side, there's 25 ma AC current going to
>>>> the transformer then to the Outguard p.s. and fan.
>>>>
>>>> Have Fun,
>>>>
>>>> Brooke Clarke
>>>> http://www.prc68.com
>>>>
>>>> J. Forster wrote:
>>>>      
>>>>> Looks like it. Does the transformer draw much current with the PCB
>>>>> removed? If it has shorted turns, as it appears, it likely will. Does
>>>>> it
>>>>> get hot?
>>>>>
>>>>> -John
>>>>>
>>>>> =================
>>>>>
>>>>>
>>>>>        
>>>>>> Hi:
>>>>>>
>>>>>> I think the power transformer got cooked.  Have a look at the Vac
>>>>>> and Ohms
>>>>>> data:  http://www.prc68.com/I/HP3458DVM.shtml#T1
>>>>>>
>>>>>> Force a browser refresh to see the latest schematic.
>>>>>>
>>>>>> Have Fun,
>>>>>>
>>>>>> Brooke Clarke
>>>>>> http://www.prc68.com
>>>>>>           
>>
> 
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