Contax RTS III Viewfinder Display Stays ON when the camera is OFF

[cuongtd]

My Contax RTS III speed/f displays (the small blue displays within the viewfinder) stay on when I set the camera in the off position, and keep on, until I remove the batteries.

If I operate the controls nothing happens, which is to be expected, and the speed and f displays do not change when I change the corresponding dials. So it seems the camera is actually off except the blue background light stays on forever.

Today, when I use the camera outside with the strong light, the camera can be turned off, as perfect. But if I use the camera inside the house, it remains the blue backlight in the viewfinder (because of the weak light).

I think the problem is one of the transistors which control the backlight of the display, I found the repair manual of Contax RX. I guess the problem was there. But the name, position of that transistor in RTS III is different.

Do you have experienced a similar problem (and have a solution) ?

More important, I want to ask if anybody have the repair manual for RTS III ? I will try by myself. May I have the scan version of repair manual?

I'm desperate now because my camera is being fault.

Thank you very much in advance.
Best Regards

 

[John Koehrer]

Does the camera have a timing circuit for the light? IE:counts 30 seconds or so and then turns off?

 

[cuongtd]

Yes, it does have the timing circuit, but it's the same with the Main Switch.
After 16 seconds, the camera goes off. I've tested in 2 light conditions:

1. Point the camera to the strong light source, The brightness of the display is maximum, after 16s with no-action, the display went off, as perfect. The same when switching off the camera when pointing to the strong light.

2. Point the camera to the normal light source, the brightness is medium, after 16s with no-action, all function went off, the blinking meter off, but the bottom display was still on, but in the frozen state, the problem occurred here. The same when switching off the camera when pointing it to the less strong light, normal light, weak light.

- This is what the display while ON (note that the light in the right meter (at LT) and the bottom display are still on)

http://imageshack.com/a/img905/2373/QQhL7P.jpg

- And this is the OFF state (light in the bottom display is still on with the whole segmented numbers.... (I don't know if the LCD is still holding the last state of these segmented numbers...). Light is dim a little bit compare to the ON state. I think the transistor is leaked, but I dont understand why the segmented numbers in the bottom are still ON.

http://imageshack.com/a/img910/1842/J6B93o.jpg

I looked at the repair manual for Contax RX, and found this schematic:

Hello,

So seemingly the circuit is of that kind that the display illumination is not switched by the main Switch, but by an intermediate transistor, with power voltage still at that transistor even when swicthing voltage for this transistor is off?

bye

Yes, 2 transistors are controlling the brightness of the display through 2 signals in the following table.

 

[cuongtd]

Today, I found out that the Viewfinder Display Backlight is controlled by EL Drive, which produces the voltage to run the backlight. The output voltage VEL is changed by the input pulse ELC (ELCLK) from CPU-1

Therefore, the way RTS III controls the brightness of LCD backlight is differed from RX (RX uses 2 control signals to activate the transistors)

I really don't know exactly the name of this EL drive. Could someone who has disassembled the RTS III help me?

 

[Jeff L]

I remembered this. Might be helpful, or the poster could help.

(there was a url link here which no longer exists)

Good luck.

 

[cuongtd]

I remembered this. Might be helpful, or the poster could help.

(there was a url link here which no longer exists)

Good luck.

Thanks, I've contacted with him, he is the person who sent me the repair manual for RTS III, I'm very appreciated. I will keep updating the process in this thread

 

[cuongtd]

Today, I figured out that the battery of RTS III got empty so quick. I think the problem is the DC-DC Converter Board.

When turned on, emits a high pitch to low grunting sound, a whistling or buzzing depending on how bright the subject I am metering. I've researched already the best I can that this is normal, common?- with all RTS III bodies. Its apparently has something to do with a frequency of the DC-DC converter inside?

 

[AgX]

-) why then are DC-DC converters of other cameras silent?

-) how can a defective converter linked to the display Illuminator switching fault?

 

[cuongtd]

-) why then are DC-DC converters of other cameras silent?

-) how can a defective converter linked to the display Illuminator switching fault?

1. I'm not sure about this so I'm asking. I think some electrical components like transistors or something else are leaking, shorted... I'm not sure.

2. As shown in the circuit diagram, the DC-DC converter controls the display illuminator through the ELCLK frequency comes out from CPU1. CPU1 is powered by the batteries, as soon as batteries are attached, CPU1 is ON using the lower clock frequency.

BATT(Vcc)====[ CPU1 ]-------ELCLK--------| DC-DC Converter (contains EL drive(display illuminator), shutter drive, Vdd for other components.....) | ========= LCD illuminators (voltage)

 

[Yashica]

I have the same issue. My DC/DC board is fried, and onto another RTS III, it's totally DoA.
Sad, but true. Would love to see the RTS III working fine, as into the 90's.

Merry Xmas.