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

[Ed Palmer]

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
>>>>>           
>