I need help

It had what I think were jumpers connected to the right and left entry RCA connectors of Phono 2 that I suppose were, in the absence of the Phono 2, to simulate it.

I also suppose that the jumpers have an specific impedance.

Those are plastic cover to protect the RCA jack from dirt, dust, oxidation or corrosion, not a shorting plug or phono impedance plug.

You can purchase them on eBay or Amazon...

OK - found a pick of Sansui RCA Phono Input shorting plugs on a later Sansui model from 1978, but you have to be registered (AudioKarma) to view the pics.

It’s the pic in the first post and the plugs have a paper instructional tag attached to them.

I don’t post there, but I recently registered because I like the site.

https://audiokarma.org/forums/threads/installed-phono-shorting-plugs-no-difference-noted-but-not-surprised.1078302/

DeKay

"Well, if working the amp without them won’t damage the amp, I’m OK."

It will not damage the amp without them. They are only necessary if you want to use an outboard amplifier or preamplifier with your unit. 

Here is what is printed on the paper instructions tag in the photo I linked above...

IMPORTANT

Do not insert these pin plugs into jacks other than PHONO.

Inserting them into certain jacks will cut sound off.

This is what they look like if you can’t see the pic (and they are shorting caps).

https://www.amazon.com/pcs-GOLD-RCA-SHORTING-CAPS/dp/B06XFJZVMT/ref=sr_1_3?crid=1VOMXQPDW1S27&dib=eyJ2IjoiMSJ9.4AkKV6LDdyfciaJhGGXJct0bK7EeEMr2ySMEGjzsTfFBfWJJMvG_QA8oSCo7mbvcbq8E9sLe93jMy1Ogylt5xzTkHZrC3WfotBUUrr1M8FwcFcghUc_rYP5nPhgip1OL5NdSRKyKcj31qiWWX7CQTSLjYGNhRWn4gn5IRplCvy7aTIG9R3Qm6BkCcyLSzUv5vnI7UDC_rGn6ZTc_Ocx8EPL7jpxE6jxm4FEbspOyCBQ.SOCHikwmfSO0QFyoUwECtE2UxBXHr9w63irlcbg83zY&dib_tag=se&keywords=rca+shorting+plugs&qid=1776623218&sprefix=rca+shorting+plugs%2Caps%2C332&sr=8-3

"That is all."

DeKay

The OP is talking about uninsulated, bare metal U shaped plugs that go into the center only of a 2 wire rca jack.