PSN-L Email List Message

Subject: Re: My broken DataQ AD converter
From: "tchannel" tchannel@..............
Date: Sun, 1 Apr 2007 16:06:18 -0600

Geoffrey, Good advise, indeed....  Thanks, Ted

----- Original Message ----- 
From: "Geoffrey" 
Sent: Sunday, April 01, 2007 3:38 PM
Subject: Re: My broken DataQ AD converter

> Someone who has reworked a PWB (printed wiring board) will most always
> leave signs like scratch marks or noticibly different solder work.
> Resistors will be cut and left in place rather than unsoldering them
> because a PWB can only take so much heat before the foil starts
> to peal away. No sense in doing unnecessary soldering. You must look
> with a magnifying glass at the solder joints to make sure they are
> well wetted and no fine hairs of conductive materials are where they
> are not wanted. No resistor should ever be burnt or the board under them.
> You really must have a schematic because the job of tracing out one 
> yourself
> can be next to impossible. In past years the manufacturers would almost 
> always
> provide schematics but today since most US industry has gone overseas
> these forign places will refuse to let you get the schematic thill the 
> equipment
> is old and obsolete.
> It is not practicle for the common man to work on surface mounted 
> technology you
> need to work on the new boards is expensive and medical like tools require 
> fine skills.
> If you like electronics as a hobby it is best to go to a university and 
> become an engineer.
> Technologist or if all else fails a Technician.
> Without the proper tools throw the old one away and buy a new one.
> You will waste your life/monies in trivial pursuits.
> ----- Original Message ----- 
> From: "tchannel" 
> To: 
> Sent: Saturday, March 31, 2007 12:29
> Subject: Re: My broken DataQ AD converter
> Well Chris, You did it again!  I hope your head doesn't get too 
> big.....But facts are facts. From way over there, in the UK?, you were 
> able to help me fix this silly AD board, here in Boise Idaho, USA.......
> I do believe you were correct at every turn....
> 1  I do think this is an older 194 8 bit board, from your physical 
> description.
> 2  The resistor numbers on the surface mount components were 1003, and 
> 2003.  Of course the two missing ones had no numbers.  But there was a 
> pattern as the resistors were in a row, something like 
> 1003,2003,1003,2003,1003,2003,xxxx,2003, so I figured the xxxx was the 
> 1003, 100K
> 3  The other missing resistor was near others which had the 2003, so I 
> figured the xxxx would be a 200K, the way it is built I could not see 
> where these resistors were in the circuit.  I soldered in the two missing 
> resistors, and it is now working!!!!!!!
> 4  I did go to AmaSeis .ini files but did not see any "Channel # listed" 
> so maybe it is always going to be Channel 1.
> and never Channel 2,3, or 4.
> 5  I do think you are correct about someone modifying the board to run as 
> a +5v and a -0, as these two missing resistors just did not fail and fall 
> off, they look like they were purposely popped off, small scratch marks in 
> their place.
> Again, Many Thanks, Ted
>  ----- Original Message ----- 
>  From: ChrisAtUpw@.......
>  To: psn-l@..............
>  Sent: Saturday, March 31, 2007 12:00 PM
>  Subject: Re: My broken DataQ AD converter
>  In a message dated 2007/03/31, tchannel@.............. writes:
>    Hi All, Looking closely at the board I see two resistors which are 
> "Open" "cracked"
>    Its a wonder it works at all, but some parts of it do work. Channel 1, 
> only puts out + voltage, just a small amount of -
>    I think that account for the AmaSeis trace showing only the top part of 
> an earthquake.
>  Hi Ted,
>         The input resistors are two 200 K in series. The offset line is 
> 100 K to the centre point. If any of them are damaged, it should not be 
> difficult to replace them. Alternatively, could you  unsolder the 
> resistors on CH4 and replace the ones on CH1? The resistor values are 
> printed on them eg 2003.
>         I get about -0.59 V on the offset line and about 90 mV on the 
> input. I suspect that this is because the ADC is not in operating mode. 
> The offset line should be -5V for +/-10V input. Check the voltage on the 
> offset line while the channel is switched on?
>    However Channel, 2,3,4 all seem to work showing both positive and 
> negative movement "In DataQ Software Only", in this software Channel 1, 
> only shows positive trace movement, and, no negative.
>         You could get this with failed resistors. Is the range 5V or 10V? 
> I suspect that the ADC may have been 'modified' for a single polarity 5V 
> signal? Can the friend who gave it to you provide any information?
>    When I connected my Sensor to Channel 2,3 or 4 Using DataQ,  I was 
> thinking it would then work in AmaSeis, but it does not.  It looks as if 
> AmaSeis will not read any Channel except Channel 1. Even though in DataQ 
> Channel 2,3,4 all seem to work fine.  If I connect the sensor to Channel 
> 3,  AmaSeis shows a trace, but the trace does not move in either direction 
> if I stimulate the sensor. This is true for Channel, 2,3,4.  Only Channel 
> 1, moves the trace in AmaSeis.
>    I think you can change the com port, in AmaSeis, but is there anywhere 
> you can or need to change for Channel selection?
>    In DataQ I closed all the Channels except Ch. 3 and saved before 
> closing.  So If I were just using DataQ software, I would be operational.
>         Amaseis normally uses CH1 only. However there are two setup files 
> Amaseis.ini and AS1.ini. It may be possible to set a different channel by 
> editing and then saving the file, but I am not sure. I know that you get 
> your different sample rates this way. If you use a Dataq and Amaseis 
> without editing the ini file, you just get 6 SPS.
>         This information is taken from an old 8 bit DI-194 board, which I 
> suspect that you have.
>         Regards,
>         Chris Chapman
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