[Test-Equipment] Tek TDS-420A Digital Scope inquiry

[Steven Bender]

Hi friends and Tech’s,

I’ve got a fairly clean TDS-420A Scope that was working on three of its four channels last year, and I put it aside due to other commitments and projects.  I recently took it out of the kitchen! and tried to power it up and - nada.  Nothing.  No fan.  No display.  Just dead.  I know that the TDS series (specifically the 420 and 460) sometimes suffered from leaking SMD Caps, but I thought that by the time these “A” versions were built, that had been discovered and corrected.

So was that an incorrect assumption?

Otherwise, I was thinking maybe high ESR in the switching power supply input caps.  Comments?

Can anybody chime in on other possible failure modes here?

Also, I recall that someone had pulled the ceramic input board with the 4 BNC’s on a TDS-420, 420A, 460, or 460A set and replaced a small SMD part or two (maybe an input cap?) and got a dead input working again, but a Google search failed to bring up his “How to do it”.  Has anyone saved the link to that, which they can post or send to me? 

Many thanks,


Steven L. Bender