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I started refurbishment of the
341A by removing the chassis from the case. All went well until
I came to the last knob. Some of the knobs have a plain bakelite
ring behind the push-on knob. The knobs came of easily but the
last bakelite ring was stuck fast by rust. Penetrating oil failed
to dislodge it. It seemed almost stuck with superglue.
Fortunately the shaft to the tuning
mechanism on which the ring was stuck was grippable with long
losed pliers and by a combination of twisting (the ring has a
circular hole in the centre rather than a D-shaped hole) and
tapping through the panel aperture from the rear began to free
it. Eventually it came off without any damage.
The chassis almost came out, but first
I had to lift up the dial glass (perspex) and waggle the pointer,
before it could be extracted.
The chassis was smothered in dust which
I removed with an old toothbrush, revealing a nice shiny surface.
The first thing of note was the twin-gang tuning condenser which
was very loose on its mountings. In fact I immediately noticed
the reason for the demise of the set. One of the wires connected
to the tuning condenser had broken off due to the excessive free
movement of the tuning gang. The thing seems to be floating on
rubber bushes which have perished and other than detaching the
tuning condenser and finding replacement bushes it may be possible
to make a securing bracket which can be screwed to the top of
the condenser and the chassis. There's a suitable anchor point
on the condenser and drilling the chassis for a second anchoring
screw for the bracket looks straightforward. I'll take a view
on whatever's feasible....
As everything else seemed to be OK,
I found a scrap IEC chassis mounting connector and soldered this
to the remains of the original mains lead, cut off by the auction
house. This enabled me to quickly test the set.
I resoldered the broken wire to the
tuning condenser and applied mains power. Switching on illuminated
the single dial lamp, followed by the valve heaters.
There was a lot of crackling which quietened
after jiggling the controls and after plugging in a long wire
I was able to tune across some of the medium waveband. Stations
were at decent strength and I guess little is wrong with the
radio. I removed the EL41 and measured the voltage at the valveholder
pins. 300 odd at the anode pin and 280 odd at the screen grid
but only about 100mVolts DC on the control grid so the audio
coupling condenser seems to be OK. I plugged the EL41 back in
and checked the other two wavebands. Both seem lively but I suspect
the shortwave band needs realignment.
The next task is to fix the tuning condenser
mounting and free up the tuning mechanism which seems too stiff,
then apply switch cleaner to the various switches and controls.
Once this is done I'll realign the IF transformers and the three
wavebands.
Just being prudent I fitted a new audio
coupling condenser as the old one had a crack running through
it. |
