Intermittant output of Burdick ECGs. 1

[scbiomed]

Over the past several years I've come across many Burdick ECGs where the operator complained of only flat line tracings or units unable to acquire input sgnals. When I hooked a simulator up and ran an ECG it would usually come out ok. Sometimes after several such runs the problem would appear then return to normal.
When signal tracing the input circuit of the main board I found analog inputs to the analog to digital converter to be good but the chip had no output. The problem lie in the clock input. The crystal (Y2) had no output. Usually replacing the crystal would fix the problem but sometimes the clock input still wouldn't get to the converter.
Further checking revealed poor thru hole plating on the pc board. Soldering leads thru these holes corrected the problem. These are the pass thru holes that take the signals from the top to the bottom of the board. In the front end of the board there may be several of these. Keep signal tracing until you find them all. The low level of the signals in this area make it more prone to this problem than the rest of the board. I've found this problem on 350i's, 800's, 850's, Eclipse's and Eclipse LE's

 

[modernbiomedical]

I have definitely seen this problem before. Thanks for the input.