However, the receiver was still lacking sensitivity and any audio resolved was very distorted. It was also clear that the AGC circuit didn’t work either. Speak to anyone with experience in old valve equipment and the first thing they will tell you is ‘re-cap it’. That is, replace any electrolytic and tubular capacitors. Over the years, the old ones dry out or leak wax. Either way, they end up being high value resistors rather than capacitors. This can have detrimental effects on system gain and AGC circuits in particular. This in mind, I began to examine the tubular capacitors in the AGC circuit. Several were reading as little as a few megohms and were duly replaced. However, following the path of the AGC voltage back from the detector was not easy and I soon ‘lost’ it. I had to conclude that what I had did not conform to the circuit diagram. The circuit diagram was definitely that of an RA17 and clearly not for the RA17L. Some more detective work turned up a series of EMERs (Electrical and Mechanical Equipment Regulations) on the Royal Signals website and one of which yielded a circuit diagram specific to early RA17s which sported a different front-end arrangement and similarly simpler AGC circuit. The reason why I ‘lost’the AGC path was because I had traced it as far as it went, replacing duff capacitors along the way. Sensitivity was still low and the audio still distorted. It was at this point that I made the decision to completely refurbish the receiver. Having seen the horrors that lay inside the 2nd VFO I decided to start with that unit. Also one of the EMERs contained a list of all the recommended modifications to be applied to the RA17, one of which centred on modification to the 2nd VFO.
