Replacement for TVS diode?

[Axtman]

I need to find a replacement for a bi-directional transient voltage suppression diode. The SA22 is obsolete. Can I just put two 1N4007 diodes cathode to cathode and call it good?

[x-pro]

1n4007 no.
1.5KE20C or 15KP26CA.

[Greg Robinson]

SA22A - the unidirectional variant is obsolete, but the type you want, SA22CA is not. Available at Mouser, Digikey, etc.

[x-pro]

In all other circuits there is no suppressor, and it works.
And it will work just as well without it.
The machine will be lighter.

[Mick Bailey]

The spec sheet shows it has a forward voltage of 3.5V. Looks like it could be there as a clipper maybe, rather than a suppressor.

[Helmholtz]

The SA22CA will do nothing below it's breakdown voltage of 22Vp.

It's purpose is to protect the FET from peak voltages above 25V.

[g1]

For all the muting and switching Fet's used in mesa amps, seems quite odd that they single out this particular position for needing protection.

[Helmholtz]

For all the muting and switching Fet's used in mesa amps, seems quite odd that they single out this particular position for needing protection.

This particular position might be the one most likely to develop signal peaks higher than the D-S limit of 35V.

[x-pro]

more options: P6KE22CA, 1.5KE22CA

[Mick Bailey]

Ah, I re-read the spec sheet and the 3.5V forward voltage drop applies to the unidirectional diodes. Makes sense. Don't know what I was thinking there......

[Axtman]

Thanks everyone for your responses. I ordered a few SA22CA TVAs and a few J112 Fets from Mouser.

Now if you would not mind explaining how they work. I am assuming the TVA and Fet slices of the top and bottom of the waveform to give distortion.

[Greg Robinson]

TVS diodes are basically fast zeners. Unidirectional are just like zeners, bidirectional (like the one in your circuit) are like back-to-back zeners.

Q13 is for muting/channel swithcing, but as a jfet, it can only handle ~25V (35V for J112). The TVS just acts as a clamp to prevent the jfet from failing.

[Helmholtz]

. I am assuming the TVA and Fet slices of the top and bottom of the waveform to give distortion.

Neither the TVS nor the Fet are used for clipping/distortion. Also see post #6.