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Damaged TCP202 Current Probes

christopherbath@...
 

Hi,

I have two TCP202 current probes that appear to have issues.

The first probe has a large DC offset and is not able to be balanced using the balance thumbwheel. The coarse adjustment in the probe appear to have been messed around with and the plastic on the trim-pot is worn out. The probe responds to both DC and AC currents however with the large offset as mentioned. The output can also be noisy and sometimes the tip of the current probe appears to act as a small speaker amplifying some sort of noise.

The second probe also has a large DC offset. If I tap the end of the probe and play around with probe the open/close latch enough then sometimes the offset disappears the probe can then be balanced properly and works normally if not moved around. The open close latch appear to be loose on this probe.

Is it likely that these probes have been dropped and the ferrite core in the current transformer damaged? Is the best course of action to replace the transformer in the probe?

Thanks,

Chris

Jean-Paul
 

Hello: I have many of the earlier current probes, both passive and active, P6021, P6022, P6302. I believe your TCP202 is similar to the old P6302.

In general the precision ferrite cores are very fragile (thin ceramic) and easily damaged by a small drop or maltreatment when closing the jaws.
This results in a hairline fracture or chip. The result is very often unfix-able offset or intermittent offset or output.

As the core is assembled onto the jaw with potting compound, the only good solution is to get a new probe.

90% of the issues are due to the core. The hall effect sensor and the amplifier. can also be damaged by high voltage transients, but this is rare.

Look for indication of chips or cracks in the polished jaw surfaces, dirt on the mating surfaces and damage to the plastic housing.

In many years, I have fixed exactly ONE, that had an intermittent cable!

GOOD LUCK!

Jon

Ed
 

Chris:

For the probe with the large DC offset, take the probe apart and make sure that everything is soldered down properly inside,especially the balance wheel and the coarse pot. Replace the pot if as you say it is worn out.
As far as the second one is concerned, it also sounds like something in the probe is intermittent. You should also disassemble and check.

During disassembly of the upper and lower probe body be very careful not to lose the small ball bearing. Also, make sure that you record the orientation of the springy metal plate inside so it can be put back in the correct orientation. It has a tendency to fall out of the body.

If there is broken or cracked plastic at the head of the probe, or if the little tab or it's mating piece is missing, you will need new plastic pieces unless you want to tie wrap it together every time you use it.

I once purchased a non working TCP-202 probe only to find that someone had disassembled and reassembled it with the head plugged incorrectly into the board (one row of pins outside the connector). It was fully functional once the head was plugged in correctly.

On older probes like the P6302 and A6302 (older versions without the coarse pot) I have had to replace the select on test resistor in the probes to get the DC offset to balance. The TCP-202 does not have the select on test resistor as it has the coarse adjust pot. The older probes are also prone to having broken wires in the metal connector.

The TCP-202s usually do not have broken wire issues unless someone has nicked or cut the cable. Do check the spring pins in the TCP-202 TEKPROBE connector though to make sure that they move in and out properly.

ed

Jim Ford
 

Good to know, as we have at least half a dozen TCP202s at work.  I did see one with the plastic at the tip cracked.  Probably could have fixed it with epoxy or something, but I think it got thrown out.I'd at least try to repair one now if it goes south on me.Thanks for posting, Ed.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Ed <@scskits> Date: 1/9/20 2:43 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Damaged TCP202 Current Probes Chris:For the probe with the large DC offset, take the probe apart and make sure that everything is soldered down properly inside,especially the balance wheel and the coarse pot. Replace the pot if as you say it is worn out. As far as the second one is concerned, it also sounds like something in the probe is intermittent. You should also disassemble and check. During disassembly of the upper and lower probe body be very careful not to lose the small ball bearing. Also, make sure that you record the orientation of the springy metal plate inside so it can be put back in the correct orientation. It has a tendency to fall out of the body. If there is broken or cracked plastic at the head of the probe, or if the little tab or it's mating piece is missing, you will need new plastic pieces unless you want to tie wrap it together every time you use it. I once purchased a non working TCP-202 probe only to find that someone had disassembled and reassembled it with the head plugged incorrectly into the board (one row of pins outside the connector). It was fully functional once the head was plugged in correctly.On older probes like the P6302 and A6302 (older versions without the coarse pot) I have had to replace the select on test resistor in the probes to get the DC offset to balance. The TCP-202 does not have the select on test resistor as it has the coarse adjust pot. The older probes are also prone to having broken wires in the metal connector. The TCP-202s usually do not have broken wire issues unless someone has nicked or cut the cable. Do check the spring pins in the TCP-202 TEKPROBE connector though to make sure that they move in and out properly.ed

Ed
 

Plastic for these probes is still available from Tektronix. Part numbers are in the probe manual. The prices are reasonable compared to a new probe.

 

On Thu, Jan 9, 2020 at 11:43 PM, Ed wrote:


For the probe with the large DC offset, take the probe apart and make sure that everything is soldered down properly inside,especially the balance wheel
and the coarse pot. Replace the pot if as you say it is worn out. As far as the second one is concerned, it also sounds like something in the
probe is intermittent. You should also disassemble and check.
Or swap the transformers and see if the faults follow.
/Håkan