Obsolete diode ---

[Valvehead]

Im looking for specs or even a cross ref number for the following obsolete zeners =

A20351 or A20357

cant find anything so far online

[g1]

Is that marked on the diode? What is the make & model of the unit it's in?

[Valvehead]

Is that marked on the diode? What is the make & model of the unit it's in?

it was from a Jose modded Marshall from years ago....the guy said the part number and then said " good luck finding those " ............... i guess they are a clipping deal on a master volume , switched in/out of the circuit

[Valvehead]

something like this---push/pull Master volume for a Marshall.........

[glebert]

I wonder if that is an actual part number or a code jose used refer to parts that he cherry picked or maybe the "secret sauce" that he didn't want others to be able to copy. Reading some posts on other forums it sounds like the normal was a 20V zener, but have seen reverences to switchable zeners at 16 or 12 volts too.

[Leo_Gnardo]

I wonder if that is an actual part number or a code jose used refer to parts that he cherry picked or maybe the "secret sauce" that he didn't want others to be able to copy. Reading some posts on other forums it sounds like the normal was a 20V zener, but have seen reverences to switchable zeners at 16 or 12 volts too.

Jose' ? As in Jose' Arredondo? FWIW I worked on a Jose' Arredondo modded Marshall 100W Bass amp many years ago (1987), wrote down the mods, didn't see anything like this.

As glebert points out, there are a number of zener values it could be. Also, he may have arbitrarily used parts, maybe "tuned by ear." If he made a deluxe version that had switchable zener choices that tells us something. Even without such a switch you can do the same. Zeners are cheap enough, try values from 12 to 20V and see whether any of these floats your boat.

Living where he did, Jose' had easy access to surplus dealers in nearby Burbank, Van Nuys, etc so we could expect him to use parts with house numbers on them he'd acquired for pennies.

[Valvehead]

Ok --Ill try some 12v to 20v and see what happens......just planning out my next amp build for 2021

[mozz]

I've found some A203xx numbers in my cross ref books, and 1 does cross to a signal diode, so that info is out there partially. You have to find the manufacturer and then maybe one of their factory books. Are they bad or are you trying to find the specs to duplicate the effect?

Edit: Mouser has that part number as their number 1086-20351 1086-20357 and they are both zeners. When i get to work on monday I will see if i can cross them.

[Valvehead]

I've found some A203xx numbers in my cross ref books, and 1 does cross to a signal diode, so that info is out there partially. You have to find the manufacturer and then maybe one of their factory books. Are they bad or are you trying to find the specs to duplicate the effect?

Edit: Mouser has that part number as their number 1086-20351 1086-20357 and they are both zeners. When i get to work on monday I will see if i can cross them.

Hmmm-- i dont see those on Mouser

[glebert]

Hmmm-- i dont see those on Mouser

I think Mozz is looking at actual books. Perhaps written in cuneiform.

[mozz]

Sorry, it was Digikey. It is part of their part number so i don't know if that's relevant.
https://www.digikey.com/en/products/...wGYCsBGEBdAvkA
https://www.digikey.com/en/products/...wGYCsB2EBdAvkA

[Jazz P Bass]

Nice catch Mozz, if it"s true.
So it appears to be a 20V / 500mw mil spec zener diode.
The difference is in the voltage tolerance.
The A20351 is a 1N968C-1/ 2% tolerance.
The A20357 is a 1N968D-1/ 1% tolerance.

[mozz]

Yeah, there is a mil spec thing going on there, so maybe it was a electronic store who sold the diodes as surplus for pennies. I will run the diode numbers at work and see if any mil #'s come up.

[Valvehead]

awesome---thanks guys

[Jazz P Bass]

The voltage 'tolerance' is what makes the item "mil spec".
It also juices up the price to about $7.00 a diode.