Have I broken my Metrastar?

[seany65]

Hello all,

Earlier today I received a Metrawatt Metrastar light meter and the needle was moving depending how much light there was, though I didn't check it against my Variosix F.

I read in the manual that came with it the bit about battery testing and setting the zero.

I did a battery test by pressing down the little silver button and moving the meter switch over it and the needle went to the red mark, so it was working.

I decided to check the zero adjustment, so I followed the manual (the same process as a bettery check but with the dial set to the 'low light' range so that the white speeds on a black background showed) and it was a little bit out.

So I tweaked the needle by turning the screw on the back and got it to '0'.

Now the needle won't move when the meter is pointed at different light levels.

Could it just be the battery ( officially a mercury 625 which is what seems to be in it) was about to run out when I did the test?

Could I have snapped or over-tensioned the spring that the needle is on?

Any help would be much appreciated.

 

[Ranchu]

I think the battery running out it a good probability, definitely put another one in there to see. Anything that will fit. Does the needle move back and forth when you turn the little zero adjust screw? If so, it's probably fine..

 

[seany65]

@Ranchu: The needle does move when I adjust the screw. I have ordered a battery from 'the small battery company'. It's a cheap alkaline battery. I know it won't hold it's 1.5v but at least it would show if the meter is still working.

It just seemed a bit odd to me that the battery would just go from 'ok' to not even moving the needle at all, when the manual shows the needle about 1mm short of the red box and saying 'battery needs replacement'.

 

[seany65]

Yup, it's dead. I fitted a new ever-ready battery in and nil, nought, zilch, bog all movement of the needle when metering and battery testing, though the needle did move when I adjusted the Zero.

Then I dropped it on on a hard floor, which wouldn't have helped much.

I'll just have to buy another one.

 

[Robert Lai]

If you dropped it on a hard floor, the needle movement has probably been jarred off its pivots. These are usually jewels, in the same manner as a mechanical watch. It that's the case, someone can dismantle it and put the needle back on its pivot.

 

[Ranchu]

I don't think it's a very good meter anyway, mine was kind of a piece of crap, imo. Went nonlinear eventually. Still working, but way off.

 

[Phil_F_NM]

My Metrastar is spot on with my Gossen Luna Pro. Both are within 1/4 stop of my Sekonic 308. Feeding the Metrastar is just a little more difficult as it eats Wein cells but I really love the meter. I'll have to get one of the CRIS adapters.
I'd say get the meter repaired if it can be done not to expensively.. They are good users. At least mine has been. Otherwise, there are certainly folks out there who need spare parts.

Phil Forrest

 

[seany65]

Thanks for the further replies.

I've got a lead on 2 others so I'm hoping they'll come in cheap enough for me to get both in case one is out or I break one.

I won't be bothering with wein cells, as the first one I bought for a yashica mat 124g didn't last long enough for me to get outside and take any pics, and the 2nd one was for a ricoh 500gx, and it lasted less than 24 exposures.

 

[seany65]

I've just bought two other Metrastars.

The needle of the first one seems marginally slower to move than I'd expect, but that could just be the way these meters were made. I did take one reading and compare it to my Variosix F and it seems to be about the same.

The needle of the second one seems to be rather inconsistant and will seem to move randomly while pointed at a single object and the meter button still hold down, with the light not looking like it changes enough for the swings. Sometimes the needle would give different readings for the same scene even when the button wasa releasded and pressed again. I did not bother comparing it to my variosix F as the needle swings etc. didn't fill me with confidence.


I think I know the answer to this question, but I could be wrong.

Anyway: Which meter would seem to be more likely to be working properly?

 

[Sarcophilus Harrisii]

Sounds like the second one has compromised switch contacts, your description matches resistance fluctuations from dirty or corroded contacts fairly closely.

 

[seany65]

Thanks for the info, Sarcophilus.

I take it that you mean the sliding switch that turns the meter on when taking a reading has dirty or corroded contacts?

Sounds like an expensive repair. I don't think I'll bother as it only cost £11.50 plus P+P.

 

[Ranchu]

You can heat the back plate with an iron or something until the glue holding it on gives way, and open it up from the back. I think the plate is inset, so you'll have to hold the iron and heat with the tip, moving it around. Pull the plastic back off with the item face down, as there are two detent pins, and they are different lengths and go in different places..

 

[Sarcophilus Harrisii]

Thanks for the info, Sarcophilus.

I take it that you mean the sliding switch that turns the meter on when taking a reading has dirty or corroded contacts?

Sounds like an expensive repair. I don't think I'll bother as it only cost £11.50 plus P+P.

I can't be certain but I do think it's definitely a possibility based on my experiences with other meters. If a cell is not responding correctly for example, then it will usually at least be consistently off at a particular light level. If a needle has come off its galvanometer jewels it will tend to stick and not move across the full range (usually including not resting at the correct null position). And often you'll see that for instance the needle tip may be dragging across the scale because the needle will no longer be more or less parallel to the scale if it has come off the pivot (usually as a result of a drop or impact damage knocking it off the jewels).

But if you're pointing the meter at a constant light source, and it's jumping all over the place, then yes, that says to me that there's a power fluctuation. Granted there are different places in the circuit continuity faults can occur. Notably the battery contacts of course. But you're not pressing the battery cover in and out. If there's excess resistance at the contacts, sub-optimal current will flow through the circuit and once again, readings will be off but they will normally be consistently off.

I suppose it is also possible that there is a poor circuit connection somewhere and that as you're moving the meter around or holding it in different orientations, this is affecting the power supply. That can happen. But, because you are using finger or thumb pressure to push or slide a switch to close the circuit, my money is on tarnished, worn or dirty switch contacts, tired springs etc (or a combination of all of the above) meaning that because their condition is borderline, as you're holding the switch on, there's some variation in conductivity across the switch contacts and it's resulting in the power oscillating. Make sense?

An easy way to test this is to support the meter against a stable surface so its position is secure. Then, without changing its position, activate the switch. Try to keep the pressure on the switch and its position absolutely constant. You'll probably get the needle sitting at a particular reading (which may well be wrong, but it likely won't be moving around). Then, vary the switch pressure a bit. Push it harder and softer. Slide it along a bit more firmly, etc. I bet you'll see the needle going walkabouts as the precise point of closure between the contacts, or the degree of pressure applied to them, varys. If so, it's a dodgy switch.
Cheers,
Brett

 

[seany65]

@Ranchu and Brett: Thanks for the replies and the info. I've not got as soldering iron, and I wouldn't really know what to do when I got the back off.

I could either chuck it in the bin, or post it to someone in Britain for them to fix. I don't know how much a fix would cost so if it's too much then they could keep it and sell it, maybe?