[Penthode]

Latest update on the 721TCS.

From the original 2020 restoration:

All the original can electrolytics are still fine with no problem That makes them 76 years old!

I left many of the original wax capacitors which pose no threat due to leakage. The ones I left are shunted by resistances 1M ohm or less and pose no DC threat.

Only two resistors changed asthey affected performance (horizonal plate resistor and video amp plate resistor.

An axial lead 40uF capacitor changed due to leakage.

Recent service:

KRK2 tuner fine tuning problem - slop due to wear in the brass tuning wand worn making it hard to tune for best sound (recall this is a split sound set). I made a new brass wand and attached it to the original tuning shaft disc. The repair fixed perfectly the fine tuning issue.

Horizontal jumping. the picture would jitter horizontally due to what appearred to be a time constant change in the circuit. Changed 6SN7 oscillator tube which fixed the problem.

Set remains working fine after regular 3 1/2 years use on all original electrolytic capacitors.

Here is a screen shot from this morning with the signal from an over the air signal via an ATSC set top box.