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Re: Short on the preAmp card
Hall D Electronics:
Hi Yves,
It sounds like a good plan. If you still have the oscillations, you
could try just putting 100 Ohm resistors at the end of the cable across
the OUTA and OUTB outputs - no postamp.
The short on the preamp (ch 9) may be due to a solder joint on the
output connector. Cleaning after assembly was very limited due to the
covers on the ASICs not being completely sealed.
Thanks and best regards,
Fernando
Yves Van Haarlem wrote:
> Hi Fernando,
>
> I tested the cable and found no short, so it has to be on the preAmp.
> I only have channel 1 and 2 connected to the postAmp (I soldered them
> to a 17-ch flat-cable connector and connected it to the postAmp) all
> the other channels I left open, so next thing to do is to connect all
> signal cables that are populated to the postAmp (in that way they are
> terminated) and see if there are still oscillations. I connected the
> heatsink to the ground of the HV-distribution board with a cable that
> has alligator clamps.
>
> Cheers,
> Yves
>
>
>
> On Sun, 9 Dec 2007, Fernando J. Barbosa wrote:
>
>> Hi Yves,
>>
>> You are right, the unpopulated channel 9 should be open. The short
>> may be either on the cable, where it is crimped to the connector, or
>> the preamp due to assembly. I would check the cable first as I didn't
>> test the cables. However, this should not impact your measurements.
>>
>> I checked every output on the cards, OUTA and OUTB, directly with a
>> scope as I didn't have any signal cables at the time. I didn't see
>> any oscillations in this manner. I will try tomorrow with a cable.
>> How are the outputs connected? Are all the outputs terminated into
>> 100 Ohm resistors? Any reference to ground?
>>
>> Thanks for your feedback and keep me posted.
>>
>> Best regards,
>> Fernando
>>
>>
>>
>> Yves Van Haarlem wrote:
>>> Hi Fernando,
>>>
>>> Thanks for your reply, my answers/findings are below:
>>>
>>>> I don't quite understand your last paragraph but channels 9
>>>> through 16 are not populated. The two ASICs on top populate
>>>> channels 1-8 and 17-24.
>>> Here are the resitance I measure (I connect the signal cable to the
>>> preAmp and measure the resistance between OUTA and OUTB on the end
>>> of the signal cable) :
>>>
>>> - 16 channels have a resistance of 950 Ohm -> those are the
>>> populated ones
>>> - 7 channels are open -> the not populated channels
>>> - 1 channel(#9) has a resistance <5 Ohm (shorted) - I believe this
>>> channel should be open because it is not populated.
>>>
>>>
>>>> You also note a block of pulses of 200 mV at 10 MHz. Is this
>>>> oscillation? Do you see such oscillation with the preamp card and
>>>> interposer powered but not attached to the HV board?
>>> Yes - if i do not connect the interposer to the HV-distribution
>>> board I just see noise (looking like bursts) with an amplitude of 25
>>> mV.
>>>
>>>
>>> Cheers,
>>> Yves
>>>
>>>
>>>
>>>>
>>>> Please let me know what you find. Thanks and best regards,
>>>> Fernando
>>>>
>>>>
>>>> Yves Van Haarlem wrote:
>>>>> Hi Fernando, Gerard,
>>>>>
>>>>> The PreAmp card and the interposer reached CMU yesterday, thank you.
>>>>>
>>>>> Today i tried to get it to work. At first i applied 3.2 V on the
>>>>> preAmp card only (no transposer) - the board was drawing 280 mA of
>>>>> current - good! After attaching the signal cable to it the current
>>>>> went up to 500 mA. Apparently the heat-sink was touching the end
>>>>> of the signal cable that was sticking out of the connector, i
>>>>> could solve this by cutting this end of as close as possible to
>>>>> the connector. After that the board was drawing a current of 290
>>>>> mA wich is OK i figure.
>>>>>
>>>>> Next thing I did was connecting the preAmp to the transposer and
>>>>> connected the transposer to our HV-distribution board. I used the
>>>>> signal cable you sent to go to our postAmp and then read out one
>>>>> channel on the scope. I saw block pulses of 200 mV with a
>>>>> frequency of 10 MHz. So I suspected another short somewhere; after
>>>>> visually inspecting the preAmp - I found a short on the output
>>>>> connector (a picture was taken but is not available yet), it was a
>>>>> piece of soldering that was easy to remove. However, it did not
>>>>> solve the problem.
>>>>>
>>>>> I start measuring the signal cable(s) for shorts - no shorts were
>>>>> measured, then i did the same measurement but now with the signal
>>>>> cable connected to the preAmp and there it was: channel 9
>>>>> (starting from 1) is shorted. Problem is that after again
>>>>> inspecting the preAmp visually I could not find anything. So my
>>>>> question - is there an obvious candidate for this short (the
>>>>> connector looks fine to me) - are there certain points i can
>>>>> measure on the board to figure this out?
>>>>>
>>>>> Thanks.
>>>>>
>>>>> Have a nice weekend,
>>>>> Yves
>>>>>
>>>>>
>>>>> /--------------------------------
>>>>> / Yves Van Haarlem
>>>>> _--~~--_ /
>>>>> /~/_| |_\~\ / Carnegie Mellon University
>>>>> |____________| / Department of Physics
>>>>> |[][][][][][]|:= / Wean Hall room 8404
>>>>> __| __ |__ \ Pittsburgh, PA 15213
>>>>> | ||. | == | | \ USA
>>>>> (| ||__| == | |) \
>>>>> | |[] [] == | | \ Tel.: +1 412 268-6949
>>>>> | |____________| | \ +1 412 641-9252
>>>>> /__\ /__\ \ Fax.: +1 412 681-0648
>>>>> ~~ ~~ \-----------------------------------
>>>>>
>>>>
>>