| Author |
Message |
    
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 25
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 05:44 am: | 
|
My project at the moment is repairing a yashica gtn, i managed to replace the pod using the microsurgery and slow speeds work fine, but the slow light never turns on, what area of the circuit should i check to find out why its not turning on? Over light works though. |
Paul_c
Tinkerer
Username: Paul_c
Post Number: 14
Registered: 02-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 03:59 pm: |
|
I have no skills in electronics but my suggestion is to check the lightbulb.If the shutterspeed varies under different light conditions or diaphragm settings
there is nothing wrong with the circuit.On arrival my Yashica GS was not functioning at all,I used some contactspray to clean the contacts on the shutter release-rod but still no effect. After one week I tried it again and everything was functioning!Electricity is always a puzzle for me............. |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 29
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 05:33 pm: |
|
would it be possible to change the bulb (which i heard was an incandescent one) to a led light? |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 271
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 05:35 pm: |
|
Should be possible, and not that difficult. You'll need a resistor in series with the lamp to limit current. You could probably just determine the value of the resistor through experimentation (my guess for a starting point would be about 1K ohms), rather than calculating its value. (And be sure to get the polarity correct.) |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 30
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 05:37 pm: |
|
I'll have to brush up on basic electronics then.  |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 272
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 05:54 pm: |
|
Pretty basic stuff.
What you need to know are 3 pieces of information: the voltage of the bulb you're replacing, the voltage of the LED and the current that the LED draws.
Then, using Ohm's Law (it's not just a good idea--it's the law!), you can figure out what size resistor you need.
Say you have a 3-volt bulb, and the LED you want to use is rated at 2 volts and draws 10 mA (0.01A). So we need to "drop" 1 volt across the resistor (since voltages in series add, and 3 = 1 + 2). We have a resistor with 1 volt across it and 10 mA flowing through it. Using Ohm's Law:
R = E / I
the resistor we need is 1 / 0.01 or 100 ohms. |
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 194
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 06:01 pm: |
|
Here is one way to design the LED based circuit for your purposes:
1. Determine the voltage across the lamp when it is on (use the good working lamp to find out). Call it Vl.
2. Choose the LED you want to install. Its data sheet will specify its forward voltage. Call it Vf. This will depend on the LED and its color.
3. Find out the LED's current rating from the data sheet or from its package and call it Il. You can expect it to be 2~20 mA.
4. Find out the resistance you need using the following relationship:
R = (Vl - Vf)/Il
If you are using Vl and Vf in volts and Il in mA, then the value of R is in Kilo Ohms. If Il is in A, then it is in Ohms. It is a good idea not exceed the current through the LED. So get a resistance that is at least the value you obtained, or a bit larger. Lesser the current, lesser the heat dissipated from the LED.
For red or orange LED, you are looking at Vf of 1.8~2.2V. So your Vl needs to be sufficiently higher than this to drive the diode. What is the voltage of the power source in your camera? |
Djamorpheus
Tinkerer
Username: Djamorpheus
Post Number: 31
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 06:44 pm: |
|
originally the voltage of a mercury battery for the electro series is 5.6 but i'm using a 6v battery. Is it foolish to buy electrical equipment and parts such as resistors on ebay? |
Aphototaker
Tinkerer
Username: Aphototaker
Post Number: 195
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 07:24 pm: |
|
For your case, do the calculations and try a local electronics hobby store. Resistors and LEDs are pretty common parts. In Radio Shack (or La Source) store chains, one can get a pack of resistors of different values and one can also get a pack of multiple LEDs.
What you want to do is to first find out physical constraints and see what kind of LEDs (width, height, etc.) you want. Then calculate the resistor values.
Then see where you can get that LED. If the usual LEDs will work, try your local electronics hobby store. In fact, try to see if you, or friends or relatives, have some broken electronic equipment lying around (music player, alarm clock, what have you). It may have the LED you want (many electronic devices have an LED to indicate ON state) and a host of resistors in it that you can reuse. It is fairly easy to check if a diode is working with a DMM or with a 3 or 4.5 battery and a resistor of few hundred ohms.
If the lamp in your camera works on full 5.6 V, it should be good to drive a typical LED. |
David_nebenzahl
Tinkerer
Username: David_nebenzahl
Post Number: 273
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 12, 2010 - 07:44 pm: |
|
@Djamorpheus: Yes, it is foolish to buy such things on eBay if all you need is a single LED and resistor. You're talking about a couple bucks' worth ($USD) of parts.
If you don't have a Radio Shack (North America: Maplin? or equivalent in UK), you can easily mail-order such components from DigiKey, Jameco or other such places.
And yes, LEDs are really easy to "harvest" from junked electronics. Just about every single electronic device made in the last 10 years has at least one LED in it, which probably still works (nobody throws something out because a LED stops working). You can just ASSume something like 2 volts @ 10mA and not go far wrong in sizing the series resistor. I've got a ton of LEDs I've cannibalized from such discards. |
Monopix
Tinkerer
Username: Monopix
Post Number: 125
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 13, 2010 - 07:15 am: |
|
I've changed them to LEDs in the past but I won't say what I used because, chances are, the OP'll end up with a different LED than I used. I think the method of calculating has been covered.
But, although it's possible the lamp has blown, there could be other reasons as well. At least, check the voltage at the lamp first. If you have a voltage and no light, then good to assume the bulbs gone. But if you have no voltage then it could be dirty contacts on the shutter release. |
