Re: DSA 602A Main Time Interpolator Died

Tom Norman

As luck would have it, a posting popped up on everyone's favorite auction site, advertising two "U400" hybrids with the 165-2078-00 Tek part number. The one I received, happily, was in working order, and it appears to be functioning correctly in the DSA. Wave forms display correctly up to the triggering capabilities of the scope, so I think this problem is fixed.

The service manual doesn't really discuss how this hybrid works, only that it is timing the difference between the sample clock and the sample strobe (probably using incorrect terms), and reports that delta to the sweep controller, which presumably tells acquisition where to place the sample data in the time record. To me, Siggi's explanation of how the TDS544A interpolator works makes perfect sense for this machine. Tek just decided to implement on a hybrid.

The hybrid itself is as you might expect, is just a chip with a few surface mount passives populated around it on a ceramic substrate. If I get some time, I'll post some pics of the little bugger...

I wish there was some way we could get Tek to release more information about these scopes. Every time I open one up, I just grin at the engineering that went into these.

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