Fluke 23 Fusible Resistor

[habanerocat]

Hi,

I have the above DMM with a blown 1K 2W Fusible Resistor on the input circuit.

Maintenance manual says to replace with the exact part for safety reasons.

But I can't find this part or get a substitute for my usual suppliers here in Ireland/UK.

Any ideas?

Thanks..............

[habanerocat]

Re: Fluke 23 Fusible Resistor

Managed to get some 10% substitutes on ebay Germany.

[redwire]

Re: Fluke 23 Fusible Resistor

How did you blow that resistor? It takes over 1,000V sustained to kill it and the MOV's would certainly also be blown.

Typically the part is a Ohmite OX102KE (1W 16.5mm) or OY102KE (2W 19mm) and has a safety function protecting the multimeter's input when measuring voltage. It's huge for the IEC61010 mains transient overvoltage spec.

[retiredcaps]

Re: Fluke 23 Fusible Resistor

http://mrmodemhead.com/blog/fluke-87-fusible-resistor/

[habanerocat]

Re: Fluke 23 Fusible Resistor

How did you blow that resistor? It takes over 1,000V sustained to kill it and the MOV's would certainly also be blown.

Typically the part is a Ohmite OX102KE (1W 16.5mm) or OY102KE (2W 19mm) and has a safety function protecting the multimeter's input when measuring voltage. It's huge for the IEC61010 mains transient overvoltage spec.

I can't remember how I blew it. Think it was a 400V motor failtfind many years ago. Let's hope the MOVs aren't blown as I haven't checked them.

Thanks for the link but getting parts from the US is very expensive.

[habanerocat]

Re: Fluke 23 Fusible Resistor

http://mrmodemhead.com/blog/fluke-87-fusible-resistor/

Yea, came across that site in a search. Very informative.

[retiredcaps]

Re: Fluke 23 Fusible Resistor

Let's hope the MOVs aren't blown as I haven't checked them.

If you made an "oops" moment, you need to check all the input protection components for damage. While some may be obvious, others are not.

1. All your MOVs should measure 0L in resistance mode.
2. The PTC should measure around 1.1k ohm.

[stj]

Re: Fluke 23 Fusible Resistor

the mov's are known to go leaky in old fluke meters.

[habanerocat]

Re: Fluke 23 Fusible Resistor

If you made an "oops" moment, you need to check all the input protection components for damage. While some may be obvious, others are not.

1. All your MOVs should measure 0L in resistance mode.
2. The PTC should measure around 1.1k ohm.

I presume the PTC you are talking about is the Variable Resistor, R1?
Or the Thermister E1/DS1?

[habanerocat]

Re: Fluke 23 Fusible Resistor

Ok, there seems to be a lot of conflicting information out there in relation to the devices in the attached circuit and photos. People on here seem to be making the most sense thankfully, so thanks.

Replaceable fusible resistor is ordered as above and on the way.

The two red MOVs, RJ1 & RJ2 are reading open circuit in resistance mode.

The yellow thermistor (PTC) E1, is also reading open circuit, so I presume this is blown.

So if I'm correct above I just need to find a thermistor which is labelled as follows.

MDC
1-2 KV
9232

Any ideas where I might identify, and/or get this?

Thanks...........

[stj]

Re: Fluke 23 Fusible Resistor

RT1 is the thermister,
RJ1&2 are mov's
E1 is a spark gap

[R_J]

Re: Fluke 23 Fusible Resistor

I agree:
E1 is a spark gap and will read open.
RJ1 and Rj2, each protect at 910v, two in series give 1820v protection These will also read very high resistance.
As long as the RJ1 & RJ2 are not blown apart and not shorted they are likely ok.
The rt1 thermistor and will measure around 1k but the resistance will increase as it heats up

[habanerocat]

Re: Fluke 23 Fusible Resistor

RT1 is the thermister,
RJ1&2 are mov's
E1 is a spark gap

Thanks, how do I test that spark gap?

[redwire]

Re: Fluke 23 Fusible Resistor

Those MOV's are hard to find because they are high voltage yet small- so they are a specialty multimeter part. The modern TDK/Epcos part would be a S05K575 but I've never found them for sale.
You can get the same voltage rating, but twice the size in 10mm. Or, you can get the same size 5mm but slightly lower voltage 820V 1mA.

The old red MOV's are GE V910LSX1399 910V 1mA, 1500V/25A, 65J, 90pF, 2.5kA. I thought a 5mm size.
Similar part Voltlog #34 – Fluke 77 Teardown & Repair, Varistor Replacement
But- he used much fatter, bigger Panasonic ERZV10D911 10mm which would not fit here.

Littelfuse bought the GE line LA series MOV and offer only larger 10mm size only like V575LA10P.

TDK/Epcos Standard MOV lineup is bigger at 10mm B72210S0551K101 7.5mm lead spacing, or 5mm B72205S0461K101 but lower voltage 750V 1mA.

Bourns offers MOV-07D821K but lower voltage 820V 1mA and 7mm with 5mm lead spacing.

You'd have to see what you can fit on the pc board. Modern parts have 7.5mm lead spacing and differing thickness, I've never found the smaller original 5mm offerings for 910V.

In your locale, there are a few electronic component distributors. MOV's, PTC, 1k 2W Ohmite OY102KE resistor Digikey Ireland or Farnell etc. sell.

[habanerocat]

Re: Fluke 23 Fusible Resistor

I agree:
E1 is a spark gap and will read open.
RJ1 and Rj2, each protect at 910v, two in series give 1820v protection These will also read very high resistance.
As long as the RJ1 & RJ2 are not blown apart and not shorted they are likely ok.
The rt1 thermistor and will measure around 1k but the resistance will increase as it heats up

Thanks, I replied above before I refreshed the page.

So are Thermistors and Fusible Resistors the same thing?
That looks like Rt in the circuit but I think it's actually R1.

[retiredcaps]

Re: Fluke 23 Fusible Resistor

So are Thermistors and Fusible Resistors the same thing?

No.

A spark gap should measure open circuit resistance.

[retiredcaps]

Re: Fluke 23 Fusible Resistor

So are Thermistors and Fusible Resistors the same thing?

No. See

https://www.youtube.com/watch?v=zUhnGp5vh60

[retiredcaps]

Re: Fluke 23 Fusible Resistor

RT1 is close by C1. See page 7-2 on Fluke 70 service manual.

https://cdn.badcaps-static.com/pdfs/...ad75dcb902.pdf

[redwire]

Re: Fluke 23 Fusible Resistor

I think I'm confused what rev this multimeter is? It's a Series 23I? I gave older 87V part numbers, that Fluke 70 service manual bill-of-materials says it's a 430V MOV.
It also gives the 1,000 ohm PTC thermistor TDK p/n 911P84E102YU13.

[retiredcaps]

Re: Fluke 23 Fusible Resistor

The Fluke 70 series I is grey. As I understand it, Fluke took the 70 series I and added better probes and made the case yellow for the Fluke 20 series I.

That's why I referenced the Fluke series I manual in the post above.