10 replies to this topic

[g0t0pless]

I'm repairing a few lights on a Beat the Clock.

Both of the lights are missing the zener diode.

I didn't have a zener on me, so I put a regular diode in, making sure to orient the band in the same direction as the old one.

The light still did not light.

If I bypass the zener diode, the light will light up full brightness, and does not shut off, even if the light isn't supposed to be lit.

Can someome please explain to me how the diode works, what its purpose is, why a regular diode didn't fix the problem, and where I can get replacements?

[zebulon]

Zener diodes are a different breed of diode from the regular type. Like a regular diode, they block reverse flow of voltage in a circuit but they also have a side effect of creating a specific voltage (when balanced with the right amount of resistance) on their output. They're like a low current (for the most part) voltage regulator. An example would be a 1N4742 which is a 12v zener diode. You can put 30v in and get 12v on the output, you just need a proper load (read big ass resistor) to dissipate the excess voltage on the other side.

 

You can order them from mouser.com or digikey.com but you'll need to know the specific part number to get the right value that you need.

[g0t0pless]

I'm hoping the manual will tell me what the correct value is. These things are too tiny to read any numbers off of them, if there even ARE any numbers.

[g0t0pless]

The manual is too blurry to read the specs on the diodes. I'm hoping the manual inside the machine is easier to read!

Edited by g0t0pless, 20 September 2013 - 03:28 AM.

[zebulon]

http://mirror2.ipdb....lock_Manual.pdf

[g0t0pless]

That's the manual that I can't read. All of the pages are clear up until the pages with diodes shown.

[zebulon]

which diode are you looking at?

[g0t0pless]

From what I can tell, every single light bulb has a zener diode on it. So it really shouldn't matter which light specifically.

 

If I recall, it was the 1st lan light at the top (it lit up a letter), and the 2nd light was "25" under the clock in the center.

 

I'd have to look at the table again to be exact.

[zebulon]

If it's black with a silver stripe it will be a 1N4004 (you can use 1N4007 in its place) If it's glass (red and clear with black stripe) it's a general purpose 1N4148....none of the diodes on the lamps are zener diodes. The zeners are just used in the regulator circuits on the board.

[g0t0pless]

1n4004 does sound VERY familiar.

[zebulon]

The 4004 are for larger loads (usually on the solenoid driver board) and the 4148 are usually for the lighter loads like the lamps. The diodes block the reverse voltage from inductive loads from feeding back into the transistors on the driver boards and taking them out.