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25th Nov 2021, 4:58 pm | #241 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Pilot Little Maestro restoration project.
Well, you did ask a fairly experienced bunch for an opinion, and that opinion has been shaped by what usually happens.
Trying to pre-think everything that could be wrong falls at the hurdle of the size of 'everything' Sure, you can get the jump on the more probable problems, but though the less probable ones are less probable, their numbers add up. There are so many of them Which ever way the survey had gone, I can't see how you could have used the result to influence what you did after seeing it. So it couldn't contribute to any increased chance of success any way, and just acts as a distraction. Statistical generalisations can tell you about the average of things you can expect of a large population, but when you're handling an individual unit, you have a population of just one, and all bets are off. David
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25th Nov 2021, 4:58 pm | #242 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Pilot Little Maestro restoration project.
Cheers ken
Well with the lamp limiter in line the rectifier peaks at 20 volts DC, Like i said the dial lamp is very dim,. Jay
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Help!! I've been electrocuted by a glass thing that glows |
25th Nov 2021, 5:38 pm | #243 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
1.2 volts from the dropper limiter still in line. Make that 30v, (bad connection) Cant see the valves glowing, But slightly warm to the touch, Lamp limiter doesn't glow bright at turn on, Well not that i can notice anyhow, Lamp is constantly dim,
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Help!! I've been electrocuted by a glass thing that glows Last edited by Radio Scotland; 25th Nov 2021 at 5:51 pm. Reason: Additional info |
25th Nov 2021, 6:05 pm | #244 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
Anyhow no explosions yet.. Jay
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Help!! I've been electrocuted by a glass thing that glows |
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25th Nov 2021, 6:18 pm | #245 |
Moderator
Join Date: Jun 2003
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Re: Pilot Little Maestro restoration project.
The lamp will glow dimly just because of the valve heater chain. What wattage bulb are you using? Anything less than 100W will probably drop too much voltage to let the radio function. Lamp limiters are really only there to prevent disasters on initial switchon - you can't expect the radio to operate normally with it in circuit.
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25th Nov 2021, 6:19 pm | #246 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
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Help!! I've been electrocuted by a glass thing that glows |
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25th Nov 2021, 9:18 pm | #247 | ||
Heptode
Join Date: Jan 2008
Location: Durham, County Durham, UK.
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Re: Pilot Little Maestro restoration project.
Quote:
Anyway I have one of these too so I’m watching with interest, good luck. John |
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25th Nov 2021, 10:09 pm | #248 | ||
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
I changed all the wax bombs as the general opinion on here is to ''change them on sight'' Unless i get advised not too she's getting the full 240v tomorrow, Jay
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25th Nov 2021, 10:40 pm | #249 |
Octode
Join Date: Mar 2015
Location: Yorkshire, England.
Posts: 1,294
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Re: Pilot Little Maestro restoration project.
Go for it Jay! I'm gunning for you! Sometimes it's just s**t or bust. We learn from our mistakes. I once measured a capacitor and then put my fingers across the terminals as I manoevered the PCB back into place; it made me jump but I pressed on. Sometimes you just have to make a leap of faith.
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25th Nov 2021, 11:38 pm | #250 | |
Heptode
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Re: Pilot Little Maestro restoration project.
Quote:
Be back soon Cheers
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26th Nov 2021, 1:24 am | #251 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
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Re: Pilot Little Maestro restoration project.
Normally, I would expect a small radio with nothing wrong with it, just to work with a 100W lamp limiter in line, however the Little Maestro has a 300mA nominal heater load which is a significant proportion of the 420mA 100W lamp nominal running current, so there could well be nothing desperately wrong with the set except being starved of mains voltage.
The lamp is dim anyway so there's obviously no direct short downstream of the lamp. If the dc from the rectifier is only 30 odd volts, what is the ac voltage on the rectifier anode? Is it commensurate with that level of HT? A 200W bulb might be a more appropriate limiter but they haven't been common for many years now. I'd just switch it on direct to mains (use a 1A fuse if you've got one) and see what happens. If something expires, at least you'll know where to look for the problem!
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26th Nov 2021, 10:24 am | #252 | |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Quote:
173 Volts DC on the rectifier, No bangs or smoke, Or burning smells, So thats something i suppose. Jay
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Help!! I've been electrocuted by a glass thing that glows |
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26th Nov 2021, 10:39 am | #253 | |||
Heptode
Join Date: Jan 2008
Location: Durham, County Durham, UK.
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Re: Pilot Little Maestro restoration project.
Quote:
But fixing is the best bit so you’ll have fun fault finding John |
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26th Nov 2021, 10:40 am | #254 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
On the original test i had the volume up full, When i turned it down to less than half way there was a buzz/hum and it seemed to be receiving with the capacitor fully unmeshed, So i connected an aerial then the fuse in the plug blew, No bangs or flashes.
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Help!! I've been electrocuted by a glass thing that glows |
26th Nov 2021, 11:23 am | #255 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Could one of the valves have developed an internal short ? Yea john now the fun begins, Especially with no valve tester..Anyhow time for a wee break from it..
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Help!! I've been electrocuted by a glass thing that glows |
26th Nov 2021, 12:37 pm | #256 |
Nonode
Join Date: Aug 2015
Location: Cambridge, Cambs. UK.
Posts: 2,196
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Re: Pilot Little Maestro restoration project.
Well at least it was making noise, which is promising.
If connecting an aerial caused the mains fuse to blow, it's a jolly good thing that you didn't interpose yourself between the set and the aerial! Three things to do now 1. Replace the capacitor that is internally connected between the aerial socket and the set input. It seems that it's no longer safely isolating the aerial from live mains. 2. Change over your mains connections in the plug so that the chassis is connected to mains neutral instead of mains live. 3. Check out your aerial. It sounds as though it's shorting to earth somewhere. Then you can safely try out the Little Maestro again. Don't be surprised if the reception seems to consist mainly of hums and buzzes. Thanks to LED lamps and switched-mode power supplies, there's usually a huge amount of intereference on AM radio these days. Martin PS It's most unlikely that your symptoms are caused by a faulty valve
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26th Nov 2021, 6:56 pm | #257 |
Heptode
Join Date: Jan 2006
Location: Cornwall, UK.
Posts: 501
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Re: Pilot Little Maestro restoration project.
The aerial should be a permanently attached length of wire (about 10 feet long) that can be stretched out but is not intended to be connected to anything else (insulation tape can be wrapped around the end). However, C1 should be a safety Class Y type just in case someone makes contact with it.
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2nd Dec 2021, 3:54 pm | #258 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
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Re: Pilot Little Maestro restoration project.
Back again after being busy with other things, Iv'e not been near the radio since it blew a fuse last week.
As for the aerial coupling capacitor thats been changed along with the rest of the wax bombs, It still has a few of those domino / postage stamp type capacitors, Maybe one of them is leaking hence the blown fuse, As for the mains lead, Chassis is neutral and the live is switched, Rectifier was putting out 173 volts, It didn't fuse instantly, So something packed in after running it for a few minutes. Buzzing and humming with the volume control below the half way setting, Silence with it set above the half way point. P.S Aerial coupling cap is 1nf, .X2 Safety caps don't seem to go that low in value, So fitted a standard polypropylene type,
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2nd Dec 2021, 4:39 pm | #259 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
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Re: Pilot Little Maestro restoration project.
You need a 'Y' cap for the aerial coupling! They definitely go that low! X caps are for 'across the mains'..easy to remember X is a cross (across).
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2nd Dec 2021, 6:09 pm | #260 |
Heptode
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
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Re: Pilot Little Maestro restoration project.
Cheers sideband i'll have another look online,
I ''Think'' i might have traced the problem. When i hook my meter across the two outside pins of the volume control i'm getting 680k, my volume control has a centre notch at the half way position, When i put it in the notch position and wiggle the volume pot shaft every now and again it goes from 680k to 44 ohms, That can't be right, Iv'e bypassed the volume pot but iv'e not tried plugging the radio in yet.
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