Title says it, any noteworthy improvements to the "A" version of the chassis?

Vertical retrace blanking and a modified contrast control I believe. I'll try to dig it up in a Wallace Teleaide.

The TS-18A is Canadian.

"TS-18, eh?"

Here's a portion of the schematic. Pin 3 of the 7JP4 is grounded in the TS-18. Here it is a fed a blanking pulse from the vertical circuit.

They also added some taps and caps to the contrast controls. Probably a few other minor tweaks.

https://flic.kr/p/2ka82XL

Thanks Bob. I appreciate it. I wonder if it is worthwhile to upgrade a TS-18 to the "A" version. Sounds pretty minor to do.

Absolutely as far as the retrace blanking goes. I've done that the every TS-4 and TS-18 chassis I've restored.

You would need a rather specialized potentiometer for the contrast mod. Probably the only source is to scavenge one from another set.

Thanks Bob!