The article by
John Ounsted referred to in the Post above did mention the fact that the
“ … glass tuning scale is not really fixed at all – it was simply gaffer taped into the cabinet during assembly being then supported more securely by the scale backing plate when the chassis was in place.” In this set the glue on the gaffer tape had turned to dust which meant that “
.. it's very likely that the glass may fall down and smash if precautions aren't taken when withdrawing the chassis for the first time after forty years.” Suitable precautions were taken – see picture below – and the glass tuning scale was safely extracted and bubble wrapped for later.
In the previous Post I also mentioned that someone had fitted an external aerial wire of sorts as I'm assuming this is not factory fitted. The internal plate aerial had a short length of wire attached to a Wander Plug? Both these wires were attached by insulating tape to the inside of the cabinet? The picture below shows this clearly and of course removing the insulating tape ripped the plate aerial: -
So chassis removed from cabinet, speaker disconnected and glass tuning scale safely stored – we can move on and do some basic electrical checks.
With a 1 amp fuse in a three pin plug I'm reading about 35Ω across the LIVE and NEUTRAL pins with the set switched-on but not plugged in of course - Service Sheet states that this should be 32Ω. No reading when the set is switched-off and still not plugged in of course. This means that the two pole mains switch is working and the Mains Transformer Primary winding is good.
The Mains Transformer Secondary winding was checked by first disconnecting one of the AC wires from the transformer to the metal rectifier and then measuring the resistance across that wire and the other on the rectifier. This gave a reading of 95.5Ω – Service Sheet says 90Ω.
Moving on to the Output Transformer I'm getting a healthy reading of 650 ohms on the Primary and 0.4 ohms on the Secondary. I note that the Service Sheet lists 5.0 ohms at point “a” and I'm getting 4.7Ω. All these readings for the OT seem to be in the ball park?
Turning our attention to the Rectifier I took all the valves out as advised by
David G4EBT with a view to measuring the AC input and DC output. After sending David on a wild goose chase the main lesson I have learned here is next time I need to look more carefully for the
~ symbols! So after that faux pas and measuring from the correct pins on the rectifier I have: -
219V A.C.
267V D.C.
So far, so good … remember all valves removed up until this point.
Next Step is to replace both C38 and C39 – A.F. coupling capacitors - before our first live test, with the lamp limiter of course.
The Service Sheet shows C39 as 0.02μF although what has been fitted in my set is 0.001μF. On the assumption that Kolster-Brandes made this change for good reasons (?) I'm going to replace like for like – just waiting on parts arriving. After that and assuming everything is ok we can move on to testing the valve voltages.