Re: Preamp & Interposer

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hall D Electronics:

Hi Yves,

I did some further testing on channel 16 and now I am convinced that the 
problem is internal to the ASIC, not from assembly issues. The impedance 
and bias on the A input of ch 16 are much lower than those of the other 
channels. As for the cause, I don't know but I don't think it is worth 
replacing the ASIC because of one bad channel given the limited number 
of ASICs.

Gerard will be sending you his on Monday and I will send him yours.

Regards,
Fernando



Fernando J. Barbosa wrote:
> Hi Yves,
>
> I could not find anything physically wrong or bad with channel 16 that 
> could have caused this failure. It may have been due to assembly as 
> this package is not sealed.
>
> Regards,
> Fernando
>
> Yves Van Haarlem wrote:
>> Hi Fernando,
>>
>> Very nice that you found the problems. I guess the bad solder joints 
>> were good when I got the interposer and became bad after a while - I 
>> am not so worried about that. But channel 16 on the preAmplifier died 
>> at some point - you can see it dying (on March 6, 2008) in the data. 
>> As far as I remember we did not do anyting to the pre-Amplifier on 
>> that day but it is already a month ago. Maybe you have an idea what 
>> could have damaged the pre-amplifier because it should be avoided in 
>> the future.
>>
>> Cheers,
>>     Yves
>>
>>
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>> On Wed, 9 Apr 2008, Fernando J. Barbosa wrote:
>>
>>> Hi Yves,
>>>
>>> I verified that the interposer had some bad solder joints and these 
>>> have been fixed. The one you have should be good.
>>>
>>> I checked the amplifier and indeed channel 16 was not working. 
>>> Further tests revealed that the ASIC A input (for negative going 
>>> signals or anodes) has been damaged. The B input (for positive going 
>>> signals or cathodes) works fine.
>>>
>>> Because I don't have additional preamp cards, I suggest that Gerard 
>>> send you his preamp and I will send him yours, which he can use for 
>>> his tests. I will ask Elke for additional funds to produce a few 
>>> more preamp cards (we have a few ASICs left).
>>>
>>> Gerard, let us know if if this works for you.
>>>
>>> Regards,
>>> Fernando
>>>