[time-nuts] FE-5680A performance - replacing fried chip

[beale]

I did something similar- momentary contact of +15V supply with one of the other pins- might have been the +5 Vin, or another signal. The 75ACT240 became very hot. I ordered a replacement 75ACT240 part, swapped it in, and the unit seems to work fine now.  Note this is the 0.3" wide device, DigiKey p/n 74ACT240SC-ND.  Confusingly, that part in 20-pin SOIC is made in two different body widths: 0.209" / 5.3 mm and 0.295" / 7.5 mm.

This photo shows the board with the smoked chip removed (U503 at upper left), before I installed the replacement
https://picasaweb.google.com/lh/photo/mF9WSGlEQjA8MqHhbPOJRdMTjNZETYmyPJy0liipFm0?feat=directlink

-john

>  -------Original Message-------
>  From: EB4APL <eb4apl at cembreros.jazztel.es>
>  To: time-nuts at febo.com
>  Subject: Re: [time-nuts] FE-5680A performance
>  Sent: 05 Jan '12 11:37
>  
>  I found it,  I used the +15 V of my triple output supply to power the
>  pin 4, +5 V input.  A 75ACT240 popped up and who knows the health of the
>  other things.
>  
>  Wish me luck,
>  Ignacio, EB4APL
>  
>  
>  El 05/01/2012 18:54, EB4APL wrote:
>  >
>  > I agree, I've seen it in a Tek 7623A with the storage on, it is quite
>  > difficult without it.
>  >
>  > Regards,
>  > Ignacio, EB4APL
>  >
>  > PD. Just trying to verify this I made some error and let the magic
>  > smoke leave the unit. It is still smelling ...
>  >
>  >
>  >
>  
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