MR or MR-4 meter?

[a.noctilux]

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11 hours ago, Namrof said:

Seems like I have a dead meter.... 🙁

Maybe it can be repaired.

I gave up because after repaired some failed without notice.

I understood that depending on the number of thousands of "on/off" since it was purchased, the "sliders" worn out.

Or some MR4 have rusty contacts when cleaned can work for a limited time, so choosing another meters is the way to go for me.

Even if I use one for fun, from time to time, I'd not rely on one MR4 as only meter.

Edited April 9, 2020 by a.noctilux

[onelensman]

I have a MR4 meter with a fault that is the reverse of that Namrof experienced. After acquiring this meter I had removed the top cover and cleaned and polished the contact sliders and circuit board traces which are prone to corrosion.

With an appropriate battery fitted, the meter needle responds well to varying light levels when the on/off switch is depressed but swings to the extreme end of the scale when the battery check slider is pushed, way past the check mark. According to the circuit board schematic there are two inline resistors in circuit, one of which may be the problem or there may be a short underneath the board due to corrosion. In my case the MR4 is usable although I also have a MR meter which has been giving reliable and accurate readings over several decades. Ultimately I guess it is a matter of luck with these old gadgets.

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[TomB_tx]

On the MR4 the push button slides a plastic part that hold the switch contact along an edge of the circuit board that acts as a guide. With continued use the glass-reinforced board wears the side of the plastic piece so that it can move sideways enough that the switch contacts miss making connection. I’ve fixed a few by building up the edge of the circuit board with epoxy putty.

The normal problem is corrosion along the copper circuit traces, so the either lose conductivity or create conductive paths where they shouldn’t.

Some I’ve fixed have held up well, while others developed various problems, including rapid battery drain.

Edited April 25, 2020 by TomB_tx

[BillXavier]

Another revival of this thread. I have an MR with a number of issues. Primarily, the test button does not move the pointer to the silver dot and turning the calibrating screw does not make any difference. The pointer hovers pretty much in the top part of the window i.e. on the test button side. The pointer moves when I press the light meter button but also mainly in the top part of the window. But it does that even when I block the window with my finger. There are guides on how to dismantle the MR but first would like to hear from users out there who might have had similar issues with fix suggestions (wishful thinking?)

[Michael Geschlecht]

Hello Bill,

Welcome to the Forum.

Is this a new battery? The meter works better with Silver Oxide batteries.

Is the voltage of the battery 1.35 volts?

Have you "exercised" both the battery test & the meter reading switches at least 20 or more times each? Even if both work just fine. 

Even though the 2 switches work on different circuits.

Best Regards,

Michael

 

Edited July 25, 2021 by Michael Geschlecht