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David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 34
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 31, 2009 - 10:29 pm: | 
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OK, so I was about to check the light meter in this camera when I discovered a fundamental problem that has me stumped.
I noticed that after putting in a fresh battery that the meter needle was deflecting even with the switch on the bottom turned to "OFF". So I took off the bottom plate and checked: even with the bottom plate off (and no possible connection between any switch contacts), the battery still deflects the meter.
The wiring seems super-simple: there's a single wire connecting the "hot" (negative) terminal from the battery holder to the switch contact. It looks impossible for any current to flow with the bottom removed, and yet it does. I thought that maybe over the years the insulators in the switch might have somehow become conductive; this seems to be the only explanation, yet an ohmmeter shows no continuity between any of the contacts.
Anyone have any ideas? Seems like the only workaround for now is to leave the battery out when not using the camera. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1030
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 01, 2010 - 05:27 pm: |
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just taking a quick peek into a 101, i don't see any obvious places where a short could occur between those two parts of the circuit - at least not from the bottom end of the camera. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 36
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 01, 2010 - 05:35 pm: |
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That's the puzzling thing. The single wire from the battery holder goes right to a contact assembly (consisting of a stack of 3 metal contacts separated by fiber insulators). I took out that assembly, so there was no (apparent) connection between the battery and the rest of the camera, and yet the needle still moved when I put in the cell.
All I can think is that there's some leakage between the contacts in that assembly. I drenched it with alcohol and let it dry, but no joy. I'm stumped. (Unless there's some other connection at the bottom of the battery holder I can't see.) |
Kennym
Tinkerer
Username: Kennym
Post Number: 1
Registered: 01-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 11, 2010 - 09:42 am: |
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hi,i have a great condition minolta xe1,the only problem is the iso dial,it turns freely,does anyone have info on how to fix this,cheers, |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 46
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 11, 2010 - 11:58 am: |
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Kenny M., you don't seem to understand just how this place works. If you have a new question, unrelated to another issue, you want to start a new thread (use the "Start New Thread" link when you're viewing the forum. |
Bossman
Tinkerer
Username: Bossman
Post Number: 113
Registered: 02-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 13, 2010 - 12:33 am: |
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The short is no doubt in the stacked contacts and insulator/spacers which form the "brushes" to the off-on-bc plate/contacts underside of bottom plate. I've had many SRT's that the meter reflected even when off and problem was solved by replacement of that assy. If you need another assy, let me know. Art.....www.flcamerarepair.com |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 52
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 13, 2010 - 12:53 pm: |
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Thanks, Art; as I indicated, I suspected that that assembly may be leaking current between contacts. I'm thinking I'd like to take apart that whole stack of contacts and insulators and give it a good cleaning, then try it again. Do you know if it will come apart, or is it glued together? Otherwise, I might just take you up on your offer. How much would you want for this assembly? |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 60
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, January 16, 2010 - 10:59 pm: |
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I'd like to announce:
Success!
The current was indeed leaking through that switch/contact assembly. Here's what I did to fix it:
I unsoldered the assembly (3 wires), then first soaked it in alcohol (methanol, denatured alcohol) for several hours to de-gunkify it.
Then I soaked it overnight in a solution of TSP (trisodium phosphate). I chose TSP because I wanted something that would penetrate the fiber insulation as much as possible, something somewhat caustic, and something that could be easily removed later by rinsing so nothing metallic or conductive would be left behind.
After the TSP soak I treated the assembly as if it were a print that was being washed. I alternately let it sit in clear water and rinsed it off in running water, changing the water frequently. I wanted to be sure to get anything ionic completely out of there. Then I took it out, blew warm air on it with a hair dryer to get most of the water off it so it wouldn't corrode, then let it sit overnight to completely dry.
I'm guessing the problem was a build-up of corrosion or something else conductive on this assembly, just enough to leak enough current to deflect the meter needle.
Today after I resoldered it back in place, I put the battery in with the switch set to "OFF": nothing! Success! The BC position puts the needle squarely on that projection, and the meter responds to light in the ON position. I think I have a functioning SRT-101.
Not bad for $5, eh? (I am allowed a little gloating here, aren't I?) |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1043
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 17, 2010 - 10:20 am: |
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Gloat away! interesting choice of chemicals too, i don't even know what the heck that stuff IS..... |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 61
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 17, 2010 - 01:51 pm: |
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Well, I perhaps gloated a tad too soon. I swear it was working perfectly last night. Today I picked it up and found that the damn thing was still deflecting the meter even with the switch turned "OFF". So much for success.
This thing is really frustrating me. I'm going to remove the switch ass'y again, and this time soak it for a good long time--days--in water, rinsing it frequently, then let it dry for at least a week.
Unless anyone else has any better suggestions ... |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 90
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 24, 2010 - 07:15 pm: |
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OK, so after another repair session here at Nebenzahl Laboratories, GmbH, I can definitely announce:
SUCCESS [with cautious optimism]
All it took was nearly another week of soaking the switch ass'y in TSP, rinsing and soaking it in clear water, then drying it for a couple of days to make sure all moisture was gone. Works like a charm now (knock on wood) ... |
Mndean
Tinkerer
Username: Mndean
Post Number: 181
Registered: 08-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 24, 2010 - 08:12 pm: |
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TSP is that stuff you use to clean walls before painting them, right? Not that my SRT has that problem, but it's nice to know at least one approach to cleaning that switch. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 91
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 24, 2010 - 08:31 pm: |
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Yes, same stuff. You normally wouldn't want to use it on anything in a camera (it's potentially corrosive), but I took a chance on this one part, and it cleaned it nicely with no ill effects.
Whatever works, you know. |
