Need help identifying a diode

digit

appreciated.

Might be 24V zener. You should be able to get a better idea from the circuit it's in.

It's in an Adcom CD player and it appears to be in the control circuit for the digital display. The diode shorted and when removed the display flickers.

scott9159 schrieb:

Maybe it was for display voltage stabilization.

1. What's the voltage now across the terminals where the diode was?
2. Is there a series resistor connected to one terminal of the diode?
3. What case/size was the diode?

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Dipl.-Ing. Tilmann Reh
http://www.autometer.de - Elektronik nach Maß.

The voltage across the terminals is 45v. The series resistor is 3.3K and it's a glass case DO-35. Looking over this information I'm wondering if it might be a 1N4124. Any thoughts? Thanks in advance.

On Wed, 03 Aug 2005 11:05:38 -0400, "scott9159" put finger to keyboard and composed:

Is there an electrolytic cap in parallel with the diode? If so, what is its voltage rating?

In the absence of more detailed information, here's a WAG. Let's assume the following:

(1) the diode is a zener (2) the surrounding circuit is a simple zener supply (3) the supply voltage is 45V (4) the series resistor is a 1/4W type designed to dissipate 1/8W (5) the display represents a negligible load when dim (???)

It follows then that the voltage drop across the resistor is about

20V. This gives a zener voltage of around 25V and a power dissipation of 156mW. Factoring in a 2:1 design margin, I'd expect the zener to be a 400mW type.

- Franc Zabkar

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Please remove one 's' from my address when replying by email.

The electrolytic cap in parallel with the diode is 47uf 50v. The display doesn't dim so much as it flickers.

On Thu, 04 Aug 2005 13:27:45 -0400, "scott9159" put finger to keyboard and composed:

The cap voltage would suggest that the zener voltage can't be more than about 35V, if typical design margins have been employed. The wattage of the 3K3 series resistor would be handy to know. Is it 1/4W?

1/2W? What other voltage rails are available for the remaining circuitry? For example, if 15V were available to the sled and spin motors, but not to the display, then this would suggest that the display voltage was somewhat higher. What type of display is it? Is it a vacuum fluorescent display (VFD)? These often have a zener derived bias voltage. Are there any display driver chips in the vicinity of the VFD?

Have you tried contacting Adcom?

- Franc Zabkar

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