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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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21st May 2020, 8:29 am | #1 |
Pentode
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Watt Torino - Cadetto Repair
Hi
Have a Watt Torino - Cadetto When switched on display light illuminates , but just getting a load Humming noise from speaker ,wonder what possible fault/cause maybe |
21st May 2020, 9:39 am | #2 |
Dekatron
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Re: Watt Torino - Cadetto Repair
Dried out main smoothing capacitors?
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21st May 2020, 10:29 am | #3 |
Pentode
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Re: Watt Torino - Cadetto Repair
i thought my self possibly capicitor fault, will take out of case later today, take a few pictures of under chassis and upload.
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21st May 2020, 5:17 pm | #4 |
Pentode
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Re: Watt Torino - Cadetto Repair
Have attached some pictures of ,couple of the capacitors do look bit frazzled
Last edited by real0real; 21st May 2020 at 5:25 pm. |
21st May 2020, 10:25 pm | #5 |
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Re: Watt Torino - Cadetto Repair
Circuit available from radio museum. I won't post it here for obvious reasons. There are no component designations shown, only values.
Change the audio coupling capacitor which is connected to the control grid of the 6V6 output valve before it causes any damage. To get rid of the hum, change the smoothing capacitors, probably located in the dual can on the left of picture 4.
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23rd May 2020, 3:41 pm | #6 |
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Re: Watt Torino - Cadetto Repair
Hi ,
Have downloaed Radio circuit , as mentioned no component designations shown ,so bit confusing , but as far as i can make out as shown in picture attached pointed out what think is audio coupling capacitor could anyone please possibly know if its correct one Clive Last edited by real0real; 23rd May 2020 at 3:49 pm. |
23rd May 2020, 3:54 pm | #7 |
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Re: Watt Torino - Cadetto Repair
You'll have to trace the wiring from pin 5 (control grid) of the 6V6 output valve and see which cap it goes to.
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23rd May 2020, 7:49 pm | #8 |
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Re: Watt Torino - Cadetto Repair
not sure if this corresponds correctly to wiring schemetic , Tried tracing from pin 5 but found a wire leads to grid , not directly to a capicitor , and found there is restance between where wire soldered and to capicitor across 2 points points there are wires from these 2 points that feed to speaker ,
Clive Last edited by real0real; 23rd May 2020 at 8:09 pm. |
23rd May 2020, 8:47 pm | #9 |
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Re: Watt Torino - Cadetto Repair
The audio coupling capacitor won't necessarily be connected directly to pin 5 of the 6V6. There may be a wire on pin 5 which goes to a tag strip to which the coupling cap is connected. The other end of the coupling capacitor should be connected to a 5000 Ohm resistor.
Also connected directly or indirectly to pin 5 should be a 250,000 Ohm resistor.
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23rd May 2020, 9:03 pm | #10 |
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Re: Watt Torino - Cadetto Repair
Neat reflex job.
Lawrence. |
24th May 2020, 5:14 pm | #11 |
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Re: Watt Torino - Cadetto Repair
Have had another look at 6V6 Valve socket , noticed there is a melal wire attached to one of pins of 6v6, this runs along length of radio and ends next to 6A7 Socket where it is connected to a capacitor , capacitor appears to have written on it 0.1 Uf and 1000V ,the capacitor is coupled together to a resistor and has a resistance of 0.281 at 20k on vault meter , pictures attached ,could this be audio coupling capicitor ?
Clive |
24th May 2020, 6:58 pm | #12 |
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Re: Watt Torino - Cadetto Repair
Looks like you're using paint to view the image. Could you try saving the picture as a jpg and uploading it directly to the forums. It'd save you having to photograph the screen, download the image from the camera and then upload it to the forums. The picture would be clearer too.
I'll check on your query.
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24th May 2020, 7:16 pm | #13 |
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Re: Watt Torino - Cadetto Repair
Looking at your picture the wire you refer to appears to connect to pin 7 ie the seventh pin clockwise counting from the spigot. Pin 7 is one side of the heaters. In this set one side of the heaters is earthed and there'll be any number of components connected to it.
You need to trace the wiring from pin 5 the control grid. If it's difficult to trace visually, connect one lead of your meter to pin 5 and probe around component leads until you find those which show a full short circuit to pin 5.
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24th May 2020, 9:45 pm | #14 |
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Re: Watt Torino - Cadetto Repair
counting back from pin 7 two pins to pin 5 , just noticed somethink not see before . there are 2 wires connected here , 1 wire easy to see goes into a small hole in chassis and disapears ,but thing not notice before as very hard to see theres a very short wire going to a resistor (meter set on 2m getting .260 ohms resistance) on the end of cetral grid ,attached picture of
Clive Last edited by real0real; 24th May 2020 at 9:52 pm. |
24th May 2020, 10:09 pm | #15 |
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Re: Watt Torino - Cadetto Repair
When was this set last used? I appreciate that it's been turned 'on' recently - because you have been rewarded with a hum ..... but do the electrolytics require re-forming or changing? Equally, there are quite a few wax-paper axial's in there too - and they are hardly [visually] pristine .... indeed, one of two look as though the end seals are no longer air-tight and ergo moisture-resistant.
Finally, the staining in the area of the mains transformer would be of concern to me too. It's a nice looking set - if it were me, I'd give it a re-cap and full service ...............
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24th May 2020, 11:31 pm | #16 | |
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Re: Watt Torino - Cadetto Repair
Quote:
The other wire from pin 5 should go to the coupling capacitor. As I said previously, if a visual check is difficult, use you meter to find which component leads show a dead short to pin 5.
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25th May 2020, 12:07 am | #17 | |
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Re: Watt Torino - Cadetto Repair
Quote:
Having said that the smoothers in this set look relatively easy to replace given that they're in a wire ended can. Replace those along with the coupling capacitor and it should be safe to apply power after checking the mains lead etc. The remaining caps can then be replaced one at a time.
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25th May 2020, 9:57 am | #18 |
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Re: Watt Torino - Cadetto Repair
Believe i may have found the capicitor
0.01uF / MFD 10nF 10000pF (MMFD) RATED AT 1500 V Attached pictures of Clive |
25th May 2020, 10:06 am | #19 |
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Re: Watt Torino - Cadetto Repair
Is that inside one of the IF Transformers?
Is the resistance from one end of that cap to 6V6 pin 5 close to zero ohms? If so it's the correct cap.
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25th May 2020, 10:21 am | #20 |
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Re: Watt Torino - Cadetto Repair
Yes found hidden inside the IF transformer , the wire from pin 5 goes directly to capacitor checked is zero ohms ,
Did also check from pin 5 to measure the resistor 0.25 Megohms to ground - o.k Last edited by real0real; 25th May 2020 at 10:27 am. |