Author Topic: Tektronix P6117 passive probe repair (THS720)  (Read 368 times)

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Offline Caaarlo

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Tektronix P6117 passive probe repair (THS720)
« on: September 05, 2019, 03:05:06 am »
After receiving an 8KV pulse (accidentally) during a measurement, not only the probe is broken, but also one of the input attenuator boards.

The Probe is mostly fine, except for the input chip resistor which actually has the resistive film (laser etched) on one side and an integrated capacitor in the other side of the ceramic substrate. The attached images show the resistor next to a 1206 SMD 000 jumper for size reference.

Well, the capacitor blew up (see the crater on the red paint) and left the resistor alone without compensation cap, leading the -3dB frequency to shrink from the original 200MHz to ~10KHZ  :-DD, so I have two choices:

1) To solder an SMD capacitor (probably ~10 pF) in parallel with the resistor

2) To get a spare resistor-capacitor chip

(and possibly a third choice: To buy a new probe  :-// )

The resistor-capacitor chip seems to be a custom part, nearly impossible to source.

Suggestions ?

« Last Edit: September 05, 2019, 03:18:47 am by Caaarlo »
 

Offline Gyro

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Re: Tektronix P6117 passive probe repair (THS720)
« Reply #1 on: September 05, 2019, 10:55:37 am »
It looks dead unless you can source a replacement custom R/C unit.

It's that size of distributed R/C for a reason. You won't achieve the same performance or ratings by just hacking some SmD Rs and Cs together.
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline macboy

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Re: Tektronix P6117 passive probe repair (THS720)
« Reply #2 on: September 06, 2019, 01:13:39 pm »
Save this link:
https://www.tek.com/datasheet/passive-and-active-probe-general-replacement-parts

For Tektronix subminiature probes (2.5mm and 3.5mm size), this hybrid is part of the replaceable probe tip (refer to photo halfway down the above linked page). In the manual for your probe, it isn't clear where this hybrid is located or whether it is included with the replacement tip part number 131–4997–01. I would assume not. The hybrid is also not listed as a separately replaceable item.

You may get lucky and find a used probe with a damaged cable or some other defect that makes it inexpensive. Hopefully then you can salvage parts from it to fix yours. Also be sure to carefully check all components in the compensation box of your damaged probe.
 
The following users thanked this post: Caaarlo

Offline Caaarlo

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Re: Tektronix P6117 passive probe repair (THS720)
« Reply #3 on: September 08, 2019, 12:22:06 am »
In the manual for your probe, it isn't clear where this hybrid is located or whether it is included with the replacement tip part number 131–4997–01. I would assume not. The hybrid is also not listed as a separately replaceable item.

Thank you ! Unfortunately, the R-C hybrid is not within the tip, but soldered on a thin pcb inside the probe body. I think I will try adding an SMD cap and see how it goes.
 


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