Need help identifying a diode

[scott9159]

I'm trying to identify a zener diode. It says 224 however the first digit
is sideways and the last two are upright. Any help would be appreciated.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

ment.com...

I'm trying to identify a zener diode. It says 224 however the first digit
is sideways and the last two are upright. Any help would be appreciated.

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

 

[scott9159]

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.

 

[Tilmann Reh]

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.

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?

 

[scott9159]

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.

 

[Franc Zabkar]

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.

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

 

[scott9159]

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

 

[Franc Zabkar]

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

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