31-07-2012, 02:27 PM
as it uses a ul41 i found and changed the grid coupling cap (c23) i also chandged c29 the filter cap.
being brave i then plugged it in via a lamp limiter nothing.nothing more than the on/off switch o/c. i did not have a 500k so fitted a 470k.
now we had life ,the vaves lit as did the dail lamp . the only output was a low distorted hum (can you have a distorted hum?) i left it running for 30 mins to see if the smothing caps would reform.on tes the res cap was found to only read 1.2mf i wired in a 47mf no more hum. injecting a signal to the grid of the ul41 gave a low tinny sound ,oh no a duff ul41 well not this time just dirty valve pins. audio stage now working ok,but still no signals,but there was a slight crackle when switching wave bands.time to check more caps c30 o.5mf hunts was leaky this is the agc cap.
as there were two others of the same type checked them as well both were leaky both are shown in the power suppy c31/c15 ,
getting some where now ,waveing the sig injector near the loop aerial gave an otput and a weak station could be heard at the bottem of the m/w band.by luck i held the chassis at the top and touched the dial cord drum ,big increase in out put.
the reason for this was the wire that eartes the varable cap had come off ,it was not obvious.i now had stations abet weak along the mw band.nothing on l/w
waveing the scope probe near the uch42 showed that the osc stopped on l/w
a new ucl42 finaly bought the set back to full working life.
there are a few things left to do ,i will change c34 the earth isolator and c33 the aerial isolator cap .the mains cable will also be changed for one with blu/brown wires,
then there is the cabinet but thats anothe story
rob t
if its made by hand it can be repaired by hand
