Watt Torino - Cadetto Repair

[Station X]

We have the correct cap at last then. Looks easy to replace.

[real0real]

Have just ordered new one, possibly take a week to arrive (the caps for the KB666 have arrived might start changing them).

[Station X]

If you're planning on restoring several radios it might be worth buying capacitors in bulk.

[real0real]

have noticed that capacitors are lot cheaper if purchased in bulk / assorted packs ,i am thinking of possibily restoring a few as enjoy doing ,but see how i get on with these as learning aswell

[real0real]

Update
Today have changed the the audio coupling capacitor , plus fitted new power lead as old one was bit dodgy ,
With reference to changing the smoothing capacitors, probably located in the dual can , is the dual can a metal cannister as in picture attached ?

Clive

[ms660]

That looks like a single capacitor, probably the reservoir capacitor, what value is printed on it?

Lawrence.

[real0real]

Little difficult to see whats written on it but looks like following any idea?

UF 3.2
?? 350
?? 450

Pictures attached

[ms660]

If it's the reservoir capacitor then 3.2uF would be too low and 32uF would be too high according to the schematic, is it connected to one of the rectifier's heater pins? What rectifier valve is fitted?

Lawrence.

[Graham G3ZVT]

On the schematic, why is the cathode of the rectifier connected to one side of the speaker?

[Station X]

There should be four electrolytic capacitors in this set. 2 X 6uF smoothers and 2 X 10uF cathode bypass capacitors. I can only see two and neither of them match those values.

I'm assuming that the 3.2uF is a smoother as it's close to the rectifier and mains transformer.

I'm also assuming that the speaker is of the energised type with the energising winding doubling as a smoothing choke.

Only way to be sure is to trace the wiring.

[real0real]

I have had a look to see which pin 3.2uF is attached to but noticed that the 80 Valve is listed as having 4 pins
https://www.radiomuseum.org/tubes/tube_80.html
where as the valve fitted has 5 pins ? so not sure which pin it is attached to have attached pictures , the pin it connects to does go to the transformer

[Station X]

That's not an 80 valve. What does it say on the label or perhaps on the envelope?

The valve and holder may have been changed either in production or as a modification.

The fact that the electrolytic cap is connected to the rectifier shows it's a smoothing capacitor.

Where does the other electrolytic cap (8uF?) connect to?

[real0real]

The valve fitted unable to decipher what it says / type have attached picture of

[ms660]

The connections shown in the photo's tally up with a 5Y3G rectifier amongst others, that capacitor is definitely the reservoir capacitor as it's connected to one of the rectifiers heater pins.

The 8uF capacitor is connected across the main HT rail.

Lawrence.

[real0real]

attached couple of pictures of 8uf attached to central grid and feeds of from the other end

[Station X]

As Lawrence says it's connected across the HT supply, so the 3.2uF will be the reservoir cap and the 8uF the smoother cap.

I'd replace them both with 10uF.

[ms660]

If a loudspeaker field coil is used in the receiver then ideally it would be good to know what the peak AC voltage is into the rectifier so as to be sure what the voltage rating of the replacement HT electrolytics should be.

Lawrence.

[Station X]

Power has been applied to this set and "that" capacitor has been changed.

The OP could measure the AC voltage from chassis to pins 4 and 6 of the rectifier, then multiply by 1.41.

[real0real]

can order 2 x 10uf as not have , both at 350v rating ? any others may need ordering ?

[ms660]

I would measure the AC HT voltage from the transformer with the rectifier removed, I don't like the look of that electrolytic.

Lawrence.