TDK 517 component - can anyone identify picture

[867B]

Re: TDK 517 component - can anyone identify picture

Hi, I found this thread researching to fix two dead functions on my 867B. I have registered to share this. I hope to help keep these awesome meters in service. Setup and component test showed only a blank screen. The junctions between the traces on the circuit board and the black conductive contacts for the rotary switch had excessive resistance. I found this by checking from the switch wiper to the first accessible point up the trace at a resistor. The worst was 8K ohms. The other dead location was roughly 2K. Other functional ones were hundreds of ohms. I fixed the connections with a couple quick touches with a solder-less soldering iron. I got all under 150 ohms. Now component test lives again!

[ljintexas]

Re: TDK 517 component - can anyone identify picture

Looks like an MOV..Over voltage protection.

[RatOmeter]

Re: TDK 517 component - can anyone identify picture

Hi, I found this thread researching to fix two dead functions on my 867B.[...] Setup and component test showed only a blank screen. The junctions between the traces on the circuit board and the black conductive contacts for the rotary switch had excessive resistance. I found this by checking from the switch wiper to the first accessible point up the trace at a resistor. The worst was 8K ohms. The other dead location was roughly 2K. Other functional ones were hundreds of ohms. I fixed the connections with a couple quick touches with a solder-less soldering iron. I got all under 150 ohms. Now component test lives again!

Whoa, dude. I hope you show back up to see this, but this advice was SPOT ON. Amazing.

My meter's symptoms were the same, but for all modes except current measurement. I'd gone through the service manual, traced through checking components, checking for obvious signs of toast and I was coming up blank.

I had never heard of the failure mode you described, but it makes great sense for how the meter was behaving. The rotary switch contacts on the PCB setup a voltage divider which feeds a voltage to an analog to digital converter in the microcontroller. That voltage level tells the microcontroller software what position the rotary switch is in and, therefore, what mode.

The wiper contact measurements I made were in the 400k to 700k Ohm range. After I ran a hot iron tip over them, none measured above 45 Ohms. Perfect sense, as I said... with terribly high resistance from the wiper contact to the resistors that make up the voltage divider... who knows what voltage the microcontroller saw. Probably pull all the way up or down, but definitely an invalid voltage, therefore invalid setting. I guess the firmware is set to just turn off the display if the mode setting is "invalid". Would have been helpful if it displayed an "invalid mode" message instead.

Thanks a huge bunch, man. One expensive and useful Fluke 863 repaired and back in service!

[Longbow]

Re: TDK 517 component - can anyone identify picture

I think the OP's unit may have had more than one problem. The switch contact issue has been around for some time. The only success I have had with this type of failure has been the use of silver paint, but it is expensive.

RT1 is a common Fluke part used in many of their meters. It is a PTC thermistor of 1.5K ohms. This part is in series with the common voltage input lead. The two red parts marked RV1 are 910 volt MOV's. If the thermistor is smoked, it might have protected the rest of the unit, or might not.