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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 8th Dec 2021, 6:01 pm   #301
Herald1360
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Nice pic, but it would look a bit more "in use" if the pointer were vertical (tuned to Droitwich)
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Old 8th Dec 2021, 6:24 pm   #302
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Video of the radio in action.

Thread can now be wrapped up mods..


Thanks again to all who helped out.

https://www.youtube.com/watch?v=0W_ybqPj7zA
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Old 8th Dec 2021, 7:30 pm   #303
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Great to see [and hear] it working after all your efforts!
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Old 8th Dec 2021, 7:31 pm   #304
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Great to see [and hear] it working after all your efforts!
Cheers
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Old 8th Dec 2021, 8:19 pm   #305
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Video of the radio in action.

Thread can now be wrapped up mods..


Thanks again to all who helped out.

https://www.youtube.com/watch?v=0W_ybqPj7zA
Thread wrapped up as requested.
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Old 9th Jan 2022, 3:10 pm   #306
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Default Enough is Enough

It's that pesky little maestro again, In total it owes me around £70, Plugged it in today and the rectifier went pop And to make matters worse i just went and bought an audio output valve for it as the old one was giving a bit of distortion after warm up.

Time to retire it to the back of my wardrobe till i win the lottery
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Old 9th Jan 2022, 3:34 pm   #307
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

What rectifier is fitted? I have a few that might be suitable
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Old 9th Jan 2022, 3:37 pm   #308
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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What rectifier is fitted? I have a few that might be suitable
25Z4G

Cheers for the offer sideband but its hit the limit of my cash outlay.



Jay
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Old 9th Jan 2022, 3:39 pm   #309
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Ok looking back through the threads, it has a 25Z4 fitted? I think I have a good one which I can check first. Yours f.o.c if any good to you.
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Old 9th Jan 2022, 3:45 pm   #310
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Ok it's a 25Z4G. I'll check when next in the W/S. Before you change it, make sure nothing has failed that might cause the rec to fail. They don't normally just go pop! Failure mode is usually low emission but that takes time. They can go heater-cathode short which can be spectacular (in terms of what happens inside the rectifier).
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Old 9th Jan 2022, 3:47 pm   #311
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Ok it's a 25Z4G. I'll check when next in the W/S. Before you change it, make sure nothing has failed that might cause the rec to fail. They don't normally just go pop! Failure mode is usually low emission but that takes time. They can go heater-cathode short which can be spectacular (in terms of what happens inside the rectifier).
The heater has gone open
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Old 9th Jan 2022, 4:48 pm   #312
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Dropper checks ok, So it must have been the heaters time to expire
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Old 9th Jan 2022, 5:05 pm   #313
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Yes, the heater may have just expired.

However, the two 2uF capacitors in parallel that you used were Class X types and I think it was pointed out at some point in this thread that they can break down for very short periods and then self heal. This just might have caused the problem.

Others have used a 4uF motor run (not motor start) capacitor in this application.
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Old 9th Jan 2022, 6:19 pm   #314
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Yes, the heater may have just expired.

However, the two 2uF capacitors in parallel that you used were Class X types and I think it was pointed out at some point in this thread that they can break down for very short periods and then self heal. This just might have caused the problem.

Others have used a 4uF motor run (not motor start) capacitor in this application.
I was under the impression they temporarily shorted before going open and kaput.

I've put a lot of hours on it recently, So think it might have just reached the end of the line
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Old 9th Jan 2022, 6:25 pm   #315
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Anyhow I was just having a moan about the money and problems it's cost me If sideband can supply a rectifier then that would be very much appreciated

Can lock this thread for good now mods.

Jay
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Old 29th Jan 2022, 2:41 pm   #316
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Default Little maestro distortion

Been hesitant about posting this as everybody is probably sick hearing about it after the lengthy restoration thread

Anyhow a problem has developed and that is distortion after it's been on for a few hours. The distortion gets worse as the volume is decreased and better as the volume is increased, Iv'e tried swapping the audio output valve for a known good one but no improvement.


My theory is the speaker as its not in the best nick and the voice coil is rubbing, Maybe its warping as the speaker heats up due to heat from the field coil. But i don't have another speaker so can't test my theory,

Any ideas ?




Cheers
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Old 29th Jan 2022, 7:23 pm   #317
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Well....if you keep the field coil in circuit and just disconnect the actual speaker connections, you can connect an ordinary speaker to the output transformer. When an energized speaker fails, it's quite normal to remove the field winding thus maintaining the HT and fit an ordinary PM speaker.
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Old 29th Jan 2022, 8:06 pm   #318
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Well... When an energized speaker fails, it's quite normal to remove the field winding thus maintaining the HT and fit an ordinary PM speaker.
Was under the impression the field coil formed part of the mains filtering circuit, Or is that done by a hum bucking winding in the output transformer ? Also not sure of the speaker impedance.
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Old 29th Jan 2022, 8:17 pm   #319
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

Just unhook the wiring from the actual speaker's voice-coil and wire an external speaker in its place; you don't need to fret about the original speaker's impedance for a test - anything between 3 and 15 Ohms will work well-enough to show if the problem is with the speaker itself.

I'd check the standing current in the output-valve too - you could have some sort of leakage going on which is upsetting the bias; in times-past I have had the cheap-and-nasty paxolin-sheet valve-sockets start to break-down after 70-odd years and this can really confuse the valve's bias.
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Old 29th Jan 2022, 9:02 pm   #320
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Default Re: Pilot Little Maestro pre war AC/DC 1939 restoration project.

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Was under the impression the field coil formed part of the mains filtering circuit, Or is that done by a hum bucking winding in the output transformer ? Also not sure of the speaker impedance.
Don't think they would ever put mains through a field coil.....50Hz buzz! Some coils form part of the DC smoothing, others are connected across the HT. Either way, just follow the instructions by G6 above.....
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