Fluke 5790A Service Mods/Updates

[Bryan]

I have a couple 5790As in the lab.
They are normally calibrated by Fluke and along the line they had some mods performed and are labled ( 2 labels):
Guard Modified PCN 4295 and Service Alert 1620 installed.  I'll bet someone here can tell me what they were about and it I need to do certain things for best performance/safety becuase of that.  I would be very appreciative.  Thanks

[measure]

I believe that PCN 4295 was a change to the GUARD functionality that improved common mode rejection. I have no idea what Service Alert 1620 addresses. Have you tried contacting Fluke?

[acstd90]

Service Alert 1620 replaces the rubber insulators that are mounted between the Mother board and the gaurd chassis / gaurd cover and the outer cover. Years of heat in the instrument would cause the rubber to start to break down. The problem is more prevelent if the fan filter becomes restricted with dirt. SA1620 is a replacement of those insulators.

[Bryan]

Thanks, I did contact Fluke & 1620 is for the melting rubber.  As for the guard modification as best as I can decipher it the Ext Guard needs to be cycled when the instrument changes from 220V range to a higher range.  The instrument indicator stays lit up but the guard is not as it indicates, cycling it off then back on  will kick it in.  I did & it does.  I was having some problems with 600V 50kHz/100kHz measurment on a 5725A, it was helpful.  Thanks for the input.