Radio Restoration

With the epoxy set on the terminal posts overnight, I started the next steps in the power supply re-build.
First, I replaced the wiring between the two (OA2) voltage stabilizer tubes to their 3.3Kohm dropper resistors as the insulation had been heat-damaged and was flaking off.
With those wires replaced, I then changed-out the two resistors forming the DC voltage divider from one of the 150v stabilized power supply rails to the centre-tap of the 6.3vAC heater supply to the noise limiter tune (6AL5 dual diode). These tubes are known for inducing hum into low-level audio circuits, such as in a noise limiter. The hum is indued from the AC heater to the cathode. To mitigate this, a small positive DC bias is applied to the heater circuit via the dedicated noise limiter tube heater winding centre-tap on the power transformer - the purpose of the resistive voltage divider here. The original carbon composition resistors forming the voltage divider had been cooked to a crisp and definitely needed replacement(!). I also replaced the 25uF 25vw electrolytic that grounds the centre tap to AC - the old Plessey part was well past its use by date(!).
Next, I installed four new rectifier diodes in place of the originals. Eddystone used two diodes in series in each leg of the full-wave rectifier circuit, this to increase (double) the overall PIV rating of the diodes, as the spec. of the original parts (Lucas-manufactured DD006's) was marginal for the voltages involved (400 PIV, 0.5A). I replaced the rectifiers with 1N4007 (1000 PIV, 1A) parts - although there is no need to double-up these rectifiers, I did anyway as they only cost a few cents each.
Although the original B+ filter capacitors appear to be working ok (typical of Eddystone sets of this era), I decided that in the interests of long-term reliability, these should be removed from service (bit left in place on the chassis), and replaced with modern parts.
I decided to use a single 47uF 500vw Nichicon part for the B+ reservoir capacitor and a dual 32uF 500vw JJ part for the B+ smoothing capacitors. I mounted the 47uF capacitor in a plastic clamp (recovered from another Eddystone set some time ago), bolted to the underside of the chassis near the rear of the power supply compartment, and the dual 32uF capacitor using a metal clamp, again on the underside of the chassis, located between the B+ filter choke and the front of the chassis. I used the existing 2BA bolts to mount these parts, and an additional 2BA bolt epoxied to the inside of the chassis side plate for the second mounting lug on the metal clamp.
I ran our of time at this point, so will leave the epoxy to set overnight, and I plan to complete the power supply re-build tomorrow.

My Geloso G.209-R ham bands receiver article is now posted to the SPARC radio museum website, here:https://sparcradio.ca/wp-content/uploads/2026/06/Refurbishing-a-Geloso-G-209-R-Ham-Bands-Receiver-with-Appendix.pdf