[time-nuts] If your 5335A is acting goofy or dead...

Orin Eman orin.eman at gmail.com
Sun Dec 28 00:06:17 EST 2014

While evaluating my LTE Lite and testing my buffer board, my 5335A started
acting goofy - random hangs/crashes etc..

This morning, the fan came on, but no display.

To make a long story short, the problem was exactly as described in Service
Note 5335A-26B.  I found evidence of overheating on the power supply
relay.  The 5V (and 3V) supply was down.  During investigating the fault, I
disturbed the power supply relay and reseated it.  The instrument worked
again.  Further investigation revealed a cold looking solder joint on the
relay socket and spread contacts on the relay socket.  About 1V was dropped
across the relay socket and the relay itself.  I resoldered the socket and
'persuaded' the contact with a small screwdriver.  All now seems to be back
to normal.

FWIW, do not believe the part number on the relay.  It is really a 6PST NO
beastie for which I have not yet found a replacement.

The above mentioned service note adds a second pair of contacts for the 5V
supply after replacing the 120V fan with a 24V fan fed from the power
switch.  This uses the relay contacts that used to be used to drive the
120V fan.  Ideally, you replace the relay and its socket as well, but good
luck finding the relay.  My unit has the 24V fan, but I have yet to do the
rewiring for the second pair of contacts, so I suspect the fix might not
last.  Still, it's 22 years since the date on the service note, so I might
have a few years.

So, if your 5335A fan comes on, but no display, check the 5V supply first
and if it's down, suspect the power supply relay/socket.


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