Help with cross ref diode

[zz28zz]

Trying to order more parts for my car audio amp repair. Need a diode. Orig part# is HZS16L -1.
Found specs on the EIC Semiconductor site but as usual, the type of factory specs provided aren't the same as what Digikey provides.

EIC specs Dynamic resistance as 80 ohms at 0.5mA. Digikey specs Impedence (max) and I don't see anything with 80 ohms. Are these 2 parameters the same thing?

Thx!

[fzabkar]

Usually the Zener's voltage and wattage are the only parameters that matter. Being 16V, it sounds like your Zener may be providing overvoltage protection.

[zz28zz]

The suffix of "1" indicates the reverse breakdown voltage is 15.6V +/-0.3V. It's used to control the -15V by controlling the base of a bi-polar transistor that steps -45V down to -15V. The -15V is used to power various op-amps in the audio section.

Wattage is not spec'ed on the EIC site. That's why I'm trying to use dynamic resistance to find a replacement but need to know if the
"Dynamic resistance at 80 ohms at 0.5mA" is the same thing as "Impedence (max)".

[fzabkar]

I would think that those two parameters are describing the same thing. Essentially it is a measure of how much the Zener voltage varies with current. Ideally the dynamic impedance (dV/dI) should be 0.

However, your application is not critical. The 56 ohm 0.5W series resistor in the collector circuit of the pass transistor would be rated for approximately 100mA ( Power = I x I x 56 = 0.5). This means that the base current (which flows through the Zener) would be around 1mA, assuming a hfe of 100. That's only 16mW. Therefore a low wattage Zener should suffice.

[zz28zz]

No luck with Digikey for thru-hole 15.6V zeners.

Found this one at Mouser:
https://www.mouser.comProductDetail/Nexperia/BZV85-C15133?qs=sGAEpiMZZMtQ8nqTKtFS%2FISyHb0gtGyWBnoQo%2F6Jejk%3D

In the description it says 14.7V, but under Vz it says 15.6V which what I need. Sent them an email to verify if the 14.7V is a misprint.

[fzabkar]

"C15" implies 15V. Also, a lower wattage Zener (eg 400mW) would have a lower impedance at 0.5mA than a 1.3W type.

Oops, I just realised that most of the Zener current would be flowing via the 4.7K resistor. That means the current would be 5mA or thereabouts.

[zz28zz]

The Mouser part is the only one I've found readily available. It's a 1.3W but I think it will work. I was a little concerned abt the +15 being different but I could always replace both diodes (for -15V and +15V). Any issues with that approach?