5. Tektronix P6201 900MHz FET probe PSU adaptor (2016)

 

The Tek 7834 and 7104 oscilloscopes include LEMO sockets at the back of the instruments that provide power for P6201 900MHz FET input probes, etc. It is impractical to keep fiddling around trying to plug in and remove the connectors which have an uncanny knack of jamming. The 7912AD provides a similar socket on the front panel. Why they could not have done the same for the 7834 and 7104 is beyond me but to save having to crawl behind these behemoths to plug in a probe every time I use it, I built a small box that extends the supply from the back of the scope to wherever it will be useful - in my case, the front of the scope.

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Tek does make 1101, 1103 standalone PSUs for these probes but they rarely come up on eBay and when they do they aren't cheap, the last one I saw was $200. At first I considered building one myself. The ripple requirement is too tight for a standard 78xx voltage regulator but the LM317 meets it and there are many low $ dual supply Chinese board kits on eBay. To get the ripple down I would need a linear supply, and a toroid transformer would be the best choice.

 

As I thought about the effort required and the expense (it would need a fairly big metal box to shield external noise), it occurred to me all I had to do was build a tiny shielded extension to the sockets on the back of the oscilloscope, and the mainframe would take care of the power for me. Total cost was about $40, mainly due to the LEMO connectors.

 

Both sockets on the back of the Tek scopes are wired together, so all that is needed is to do the same on the extension. Note - the Tek 1101 PSU schematic depicts a 4-way connection, but the P6201 probe only needs ±15V, therefore unless this is for a probe with a specific need for a +5V supply, there is no need to add this. The manual for the older Tek 1100 PSU has a schematic, and the later manual for the 1101A has a definitive pinout (see pdfs below).

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Mating Lemo male plugs (on lead from P6201):

Tek 131-0778-00 Lemo 4-pin probe cable plug = Lemo FFA.0S.304.CLAC42, which is the same 4-way connector as the PSU plug on the end of the P6201 probe (2 used at $6 each).

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P6201 chassis connector e.g. on 7834/7104:

Tek 131-0771-00 Lemo 4-pin probe PSU socket = Lemo ERA.0S.304.CLL, which is the same 4-way connector as the mainframe probe PSU socket (one new at $18).​

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The box I used was the smallest I could find (45 x 45 x 19mm) that fits below the Tek oscilloscopes, see photos. As with many things the cheapest supplier I could find was eBay China for just $1. I would have preferred conductive black to anodised non-conductive pretty gold, but at this price who's complaining? I did have to expose bare metal to ensure all connectors and all sides of the box are connected (for EMI prevention), but this was a minor inconvenience.