    
Riccardo
Tinkerer
Username: Riccardo
Post Number: 4
Registered: 12-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 06, 2008 - 07:06 am: | 
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I acquired a praktica LLC which has a broken meter. I cleaned the contacts, checked the battery contacts and the most obvious things, but the behaviour remains the following: the reading is either totally low or totally high. I can control if high or low only with the shutter spped / film sensitivity dial (which, once opened, act upon the same lever and variable resistor). THe diaphgam doesn't do anything, even when next to the tme that made the needle go up or down. this is very strange. This happens both when I select open diaphgram reading or stop-down, which is even stranger.
By checking with an ohmmeter on the contacts around the stopòdown switch and I could check that the diaphgram simulation resistor gets transmitted, since I can check a variable resistance, the same goes for the cell, which seems to react to light.
Still, the bridge seems to be totally unbalanced?
I even moved the trim-pots back and forth, knowing that I could un-adjust the readings, but sometimes the suffer stickage.
I would appreciate suggestions or even more an electric diagram. I found one for a praktica but only for the model with stop-down only.
Some sanity value checks might be also good, maybe some resistor is totally bad. |
