Mystery components on Traynor Bassmaster Mark II YBA-1A?

Hello all. This is my first post.

I recently bought a Traynor Bassmaster Mark II YBA-1A, circa approx. 1973.

In looking at what's on the tagboard, and at schematics online, I see two components I don't recognize.

In the schematics, they are drawn like some kind of multi-section diode or something. Looking at the actual items on the tagboard, they look more similar to a couple of axial electrolytic caps.

They are strapped in series across the primary winding of the OT.

You can see them in the schematic at this link:

I tried to attach the schematic to this post too (new at this - not sure if I'm attaching right).

The part numbers are hard to read on the schematic, but just to be clear what I am talking about: look for the two parts with numbers close to "SRS20SP20-B20" and "6RS20SP7B7".

What are those things? What is their purpose in this circuit?

Many thanks for any insights.



  • traynor_bassmaster_mkii_yba1c.pdf
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The schematic symbol used is actually very descriptive.
It shows back to back diodes with the upside down "L" shape along side indicating a rapid switch at its rated voltage.
Today it would be called a "Transzorb" (Transient Voltage Suppressor), more specifically (in this case) a Bi-directional Transzorb. Their function is as John describes.

This Traynor circuit:
Shows them as Varistors rather than Transzorbs.

I am not sure if the devices actually fitted are Transzorbs (and if so if they are Uni or bi directional). Bi-Directional voltage clamp is not really required.

You will see 2 other variations of this sort of protection, MOV (Metal Oxide Varistor) and a simple reverse biased high voltage diode (or several diodes in series reverse biased). The simple reverse biased high voltage diode clamps any voltage trying to spike negative (below 0V).

The 6RS part numbers are GE Parts, the other schematic linked above shows IR Part equivalents but equally unreadable.

A factory note described them as "surge diodes" and recommended removing them. You will note that later Yorkville Sound products (Traynor Amps) did not use them.


P.S. Boobtube post above shows they are Uni-directional transient voltage supressors.
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