Re: THS710 Repair and (future) upgrade to THS720P

Kevin Oconnor

Nice job restoring one of Teks real gems. The THS series of fully isolated channel portables makes some HV testing a walk in the park. Think of analyzing primary and secondary circuits of a SMPS using a common ground bench scope!
Don't over engineer the battery pack though. I published an article in the Feb 2018 issue of Nuts & Volts (p. 20) on this very topic! So long as you don't want to use an external charger, which is rare, you might try my method for building a spare. I used 4 off-the-shelf 3000mAhr NiMH 'C' cells with top bumps and 1" shrink tube. The only soldering/welding is to the top of the top cell to reattach the positive strap and band. The scope cap insures cell connections like in a flashlight. The ~50mA charging current is ok for NiCd or NiMH, and the latter has no memory effect.
Can you elaborate on the display used in these scopes? I've never opened one. I'm curious about the backlight method used and whether a dim display can be improved in a reasonable manner.


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