Asahi Pentax SP500

Mauro

Mauro

Mauro
Local time
12:39 PM
Joined
Mar 15, 2006
Messages
489
the lightmeter of my beloved Asahi Pentax SP500 has started working crazy: the lightmeter needle is Always poninting +, no matter the real light situation.
This has happened without any prior notice: last Saturday I was using the camera and the lightmeter was OK, yesterday I noticed the problem.
I know that the camera can take beautiful pictures without its lightmeter, but it is sad to lose this function.
Any tips and help is really appreciated.
 
Is the meter out of range? With some older SLRs that will do it. The manual will inform the measurement ranges, double check that the settings are within specifications. Reversed battery polarity can also produce the same result with some types but you mention the fault has manifested itself spontaneously, so...
Cheers,
Brett
 
Sarcophilus Harrisii said:
Reversed battery polarity can also produce the same result with some types but you mention the fault has manifested itself spontaneously, so...
Click to expand...

just to add my experience: in the spotmatic series, inverted battery polarity will only lead to inverted meter needle movement.

also, the measurement circuit in the spotmatics is of the bridge type - it's independant from the actual battery voltage. this leads me to the assumption, that there is a broken wire or a problem with the contact in the switch. does the needle react at all, or does it stick at the end of the range?
 
sebastel said:
just to add my experience: in the spotmatic series, inverted battery polarity will only lead to inverted meter needle movement.

also, the measurement circuit in the spotmatics is of the bridge type - it's independant from the actual battery voltage. this leads me to the assumption, that there is a broken wire or a problem with the contact in the switch. does the needle react at all, or does it stick at the end of the range?
Click to expand...

Thanks for the quick reply!
the needle stick at the end of the range, and it does not react to light variation.
 
I don't have one any longer (the whole "turn on the meter" bit does my head) but from recollection the needle moves with changes of settings even if the meter is off. Is this true for yours? and of not, I would be tempted to give the camera a sound but not too solid hit, in case it's just the needle stuck.

I should also say my current Pentax head count is 5, it's only the Spotties that drive me nuts - the earlier and later Pentaxes I find really nice.
 
Mauro said:
Thanks for the quick reply!
the needle stick at the end of the range, and it does not react to light variation.
Click to expand...

That's all very well, but you still haven't informed us whether the settings are in a measurable range. Are they? What is the ASA set to? What is the shutter speed set to? It's quite possible that there is an actual fault with the metering system but you always check the easy things, first.

Why bother asking for advice, if you're going to ignore it when it's given?
 
if the speed and ISO setting are within metering range, and the battery is still good, and the needle still doesn't react at all, the described behaviour indicates a broken circuit (no electrical current).
switch, wires, the meter itself, the CdS cell, or the battery contacts. close to impossible to find out which without opening and looking for the components.

still need to check:
- metering range
- battery
 
The ISO is set to 100, speed is 1/125: the needle is stuck to +, no matter the light variation and the aperture of the lens (btw, I am testing it with a Helios 44 58/2 and a Pentax 55mm with the same bad result). The battery is a AG3 alkaline, with a rubber ring to fit the battery case
 
I don't have any suggestions, but wish you luck - an SP500 was my first SLR in the mid 70s, and I still have a soft spot for them.
 
I have just tested the camera with a new battery, with the same negative result: when I switch on the lightmeter, the needle in the viewfinder suddenly jumps to +.
the camera is set to 100 ASA and the speed is 1/125: I have changed the lens, and I tested under different light but the needle always jumpt to +.
crazy, isn't it?
 
ah, moment, it jumps to +
then the circuit might be shorted (instead of broken), or the cell is dead (always too low resistance).
sorry, my mistake not to read carefully.

i still have a spotmatic lying around for parts - last time i turned on the meter, it worked rather well.
 
My Spotmatic had a meter problem similar to yours. I had to send it for a CLA, one of the CDS cells had failed. It was replaced and works fine now.
 
It sounds a bit like the problem I had with my SP1000. Although everything looked OK in the battery compartment, the meter suddenly stopped responding to any changes of shutter speed or aperture and it turned out there was actually a build-up of corrosion between the battery terminal contact in the baseplate and the one in the base of the camera itself. (Obviously you have to remove the baseplate to get to that problem but that's just a case of removing a couple(?) of screws and lifting it off.) I cleaned off both contacts with switch cleaner and everything was fine again. If it's of any relevance, I'm using zinc/air hearing aid batteries held in the ring from an old PX400 Wein cell.
 
Dear friends thanks for all your comments and advices.
I think that repairing the lightmeter can be an expensive operation, and i am not willing to put my hands into it: i have decided that I will continue using my beloved Spotmatic with a hand held lightmeter (btw i own a nice Gossen Sixon 2, and a Leningrad 7)
 
Mauro, you may want to first try pulling off the bottom plate like Mark described - it might be a simple fix.
 
The pictures in the first post on this thread give an idea of how the battery holder in the baseplate makes contact with the camera itself:

http://www.rangefinderforum.com/forums/showthread.php?t=123749

(Four screws to take off the baseplate by the looks of things.) My SP1000 had a build-up of what was almost certainly something from a leaking battery on the baseplate contact, disrupting the connection to the meter, even though the battery compartment itself looked fine.
 
You must log in or register to reply here.
Back
Top Bottom