RA17 page 4

Once you get the 2nd VFO out, it is is in fact one of the easier units to work on. The vertically mounted tag-board can be removed quite easily. Personal experience told me to expect resistors that have been stressed to be in excess of 10% high with some being as much as 50% high. Looking at the amount of wax that had pooled at the bottom edge of the board and the exceedingly grotty state of the three capacitors, I was expecting to find some seriously out of spec components. I was not disappointed, although Interestingly, the capacitors were not as bad as expected but one of the carbon resistors was 50% high in value.

However, I did not expect this (below). Such had been the heat from the wire-wound resistor that the paxolin board had literally turned to charcoal . . . Woops!

No problem! A sheet of plain fibre-glass board and some double-sided PCB pins, and half an hour later I had a new board. Note that the 33K resistor has been replaced with an RF choke, in line with recommendations in the EMER. This increases the volts on the Anode of V12. The wire-wound resistor was retained since it had not altered in value.

The photograph on the right shows the refurbished 2nd VFO. Note the adjacent filter board. In line with recommended instructions, the 470R resistor has been replaced with two 1K resistors in parallel. The original intent is to reduce the amount of heating incurred by the original half-watt resistors. I should add here that nowhere in my refurbishment did I use anything less than 0.75W resistors and in most cases 1W resistors were used. I re-installed the unit and was delighted to find that the receiver sensitivity was vastly improved. The audio however was still rubbish. Obviously still something wrong somewhere . . . Hmm.