Ultra EU4052.

[FERNSEH]

The Ultra EU4052 is the export version of the popular model T405. The main difference is the waveband coverage. Short and medium wavebands but no long wave reception.
The set I'm repairing was not working on the medium waveband although the short waveband was working in a fashion.
There was -11 volts DC on the signal grid of the frequency changer valve. Where was that coming from? Changed the X76 valve, but no improvement. The oscilloscope revealed that there was leakage coming through from the local oscillator, I was beginning to think the waveband switch might possibly have insulation failure. There is an aerial coil pack on the extreme left of the chassis, close to the tuning capacitor. It was unscrewed so it could be inspected. Switched the set on again and the fault persists. Next, a jumper wire was connected between the coil pack and the tuning gang frame, voila! results at last.
So at least I'm on the right track to getting the set working again.
Then I realised it was the tuning capacitor frame that wasn't making a connection to the chassis. A piece of wire has been soldered to the capacitor and a convenient point on the chassis.
The alignment of the aerial and oscillator circuits will have to checked particularly on the short waveband.
Strange why set worked on short waves during the fault condition.

DFWB.

[Techman]

Originally Posted by FERNSEH

Strange why set worked on short waves during the fault condition.

Probably a bit of stray capacitance that was just enough to make it work at the higher frequencies, but not enough for the lower frequencies.

[FERNSEH]

In fact the fault was a bad soldered connection on the earthing tag on the tuning capacitor. It's very difficult to gain access to the connection so the new wire link will remain in place.
Attachments show the aerial coil pack and the underside of the receiver.
Note the output valve cathode bypass capacitor is showing signs of distress.
The capacitor is rated at 12volts and the bias voltage is 13.4volts.

DFWB.

[FERNSEH]

The single pole on-off switch operated on the neutral side of the mains which means that the chassis was live when the set was switched off, that's not a very desirable condition. The on-off switch has been rewired so that it is the live side is disconnected when the set is switched off.
For the sake of safety this one of the instances where originality has to disregarded.
I suppose we have to accept these old sets were designed when the mains plug was the reversible type.
Much better just unplug the set when it's not in use.

DFWB.

[FERNSEH]

As the Ultra radio set may be used as a display item I've suggested to the owner of the set that rather than rely on a 1amp fuse in the plug it will be desirable fit a fuse inside the set for extra protection.
Because 20mm fuses are readily available that's the type that will used rather than the older 31mm fuses.

A good idea?

DFWB.

[Tractionist]

Originally Posted by FERNSEH

As the Ultra radio set may be used as a display item I've suggested to the owner of the set that rather than rely on a 1amp fuse in the plug it will be desirable fit a fuse inside the set for extra protection.
Because 20mm fuses are readily available that's the type that will used rather than the older 31mm fuses.

A good idea?

DFWB.

An excellent idea David ..... and a nice looking set.

[FERNSEH]

The Pilot Little Maestro will also have an internal fuse fitted. A 1amp fuse in the plug is fine but fuses of that value are rarely stocked by retailers.
The HMV 1360 I'm presently working on has fuses in the mains live and neutral.

DFWB.