Tube Radio Australia
RS-111 Restoration

Some time ago I came across a CEI RS-111. As this set had some historic significance, I brought it home to see if I could resurrect it.
Much to my surprise it sort of worked so I decided to give it some attentions and get into tip top shape.
I finally decided to do some work on it and started by finding information as it seemed to be a very interesting mix of golden boxes so I knew that I had to find a manual.

After some initial tests I found that the top two bands were as deaf as a post, so I started to focus there.
To clarify how this receiver is constructed it effectively has 4 front end tuners, 30 to 60 Meg, 60 to 300 meg, 500 to 700 meg and 700 to 1Gig.
The tuning front ends are works of art in themselves. The traditional tuning cap is replaces with a spiral inductor and these are very smart, the wipers do suffer and needed some attention as the wipers have broken on a few of the inductors.
They are stacked so they act like a filter / tuner.
The top band was somewhat of a mystery to me when I first looked at it.
The input BNC had a wire about ĺ of an inch long from the centre terminal and soldered to ground.
Effectively this was a dead short, but after some though @ 1 Gig itís a coil.
The next three stages in this tuner were not directly connected and are coupled through cavities in the shielding between the capacitors.
Very clever, and effectively, a Filter and tuner in one unit. The tuner then has an oscillator build in that mixes and provides this signal to a converter box.
This was where my first challenge stared. This converter takes an 80Meg signal and converts it to 21.5 megs, then it is fed into the first IF.
Interestingly enough there are four independent oscillators one for each tuner and the top band has the higher oscillator frequency hence the down converter that takes the signal to the required 21.5 Megs for the IF.
Now my issues involved changing a number of the Nuvistors as they were weak and then re-aligning the tuners and down converter.
I used a sweep generator to do this.

After getting the signal going through the tuned and filter stage, and then through the converter stage, I still had poor sensitivity on the top bands.

Both go through the down converter and I suspected an issue in the down converter.
As it turned out this was not the case. In the IF input stage three inputs go the three shielded cable inputs.
They all go to two filter stages with a coil and cap, the coil is adjustable. Now I found that the input that went to the down converter for the top two bands had a faulty fixed capacitor,
so when I passed a 21.5 Meg signal into that input the gain at the IF out was well down.
After replacing the cap and re-tuning the coil, gain on both inputs was the same and the top two bands came to life.
Of note, Do not play with the horns and caps in the top tuner. There placement and the way some of the fingers in the capacitors are bent is critical and if you play with them,
it will never track correctly again.
Also if you need to replace any parts here, they must be routed in the same way, and the same type of component.
Most of the caps here are very high quality and should not need to be replaced.

Inside View with the PAN adapter removed

IF section removed exposing the Video Modulator

1st Converter and 1st RF deck

Below the IF

PAN adapter

Front of the RS-111