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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 6th Feb 2018, 1:27 pm   #1
DigitalNoMore
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Default Pilot Little Maestro T105

I acquired this set about a year ago and thought it was about time to see if I could get it going. The case was in very good condition but the electronics a complete unknown.

A prod around with my DVM showed that all the valve heaters were okay but the pilot bulb (10V, 0.2A), connected in series with the heaters, was open circuit. The smoothing electrolytics and the output valve cathode bypass electrolytic were all leaky. In addition, six of the resistors had gone high and out of spec. Most notably, the mains dropper wirewound resistor was way out of spec.

First of all I decided to try and reform the two 47uF smoothing capacitors in situ after first disconnecting them. I picked up the mains supply in the radio and fed it to each capacitor in turn via a 1N4007 diode in series with a 10k current limiting resistor. I fed the mains supply to the radio via a variac which I gradually ramped up to give the max working voltage on the capacitors. Fortunately the leakage current to each smoother dropped to about 0.1mA after around 8 hours so reforming was deemed to be a success.

Next job was the dropper resistor. I removed this and completely dismantled it. The taps of the winding are made by means of copper collars which loop round the coil and are then bolted in place. I cleaned up the winding and copper collars (all very grimy) and then replaced the collars on the winding in order that the correct resistance values were obtained on the tappings.

The output valve cathode bypass electrolytic and all the faulty resistors were then replaced. The pilot bulb was replaced with a 12V 0.2A which was the nearest I could find. For good measure, a squirt of Servisol was applied to the wavechange switch and volume pot.

I then took the plunge and powered up the radio through my variac and lamp limiter and monitored the current with a current clamp.
Thankfully all seemed okay and the voltages around the valves looked good. Stations on both wavebands could be received with reasonable volume too.

The only problem was a fairly loud hum even with the volume control down at zero. This caused a nasty modulation with the volume turned up.
One resistor I hadn't replaced was the grid leak bias to the audio preamp valve. This had read 13M as against the 10M it should have but I'd thought it was probably okay.
Shorting it to ground though pretty much got rid of the hum so I decided to connect a 1.5M resistor across the 10M. This did the trick and brought the hum down to a reasonable level as well as getting rid of the modulation. It was also high enough to not roll off the low frequencies significantly.

Finally I did a quick alignment on both wavebands and that was it finished. Quite a nice sounding little radio considering it was a budget offering when it came out. A time consuming repair but very satisfying.
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Old 6th Feb 2018, 1:31 pm   #2
DigitalNoMore
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Default Re: Pilot Little Maestro T105

Also forgot to mention, I replaced all the waxies as the majority of them were found to be leaky!
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Old 6th Feb 2018, 4:19 pm   #3
David G4EBT
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Default Re: Pilot Little Maestro T105

An interesting write-up on a methodical restoration of what - to my eye - is a pretty little set, but beauty is in the eye of the beholder, and the colour won't be to everyone's taste, nor would it have been when it went on sale in 1956. I've trodden a similar path with the same model, which I acquired about five years ago at a Golborne Swapmeet in quite a sorry state. Given that the cabinet is actually brown Bakelite, sprayed 'sky blue' and trimmed with gold, I'd mistakenly assumed that someone had done a not very good DIY spray job on it, but I discovered that they left the factory in that.

It's not perhaps appreciated today, but back in the postwar era, Bakelite was looked upon as inferior and cheapskate alternative to wood as well as being sombre, (some radios were offered with either a Bakelite cabinet or wood, with the wooden ones being more expensive). I wonder if Pilot painted it blue to make it look more cheerful and attractive? 1956 was the year that F.J. Camm launched 'Practical Householder' and the term 'contemporary' came into vogue - down came curtain rails, doors were flushed with hardboard and painted bright yellow, with chrome and plastic doorknobs replacing Bakelite ones. A bright blue radio would sit well with that trend.

It's remarkable when looking back, to realise just how expensive small table radios were. The 'T105' retailed at 12.19s. 6d, which in today's terms equate to 315.

A decent wage for a skilled working man back then would be no more than 10.00. (I was a second year apprentice in 1956 on 2.75 a week).

Pilot certainly made full use of the 'Little Maestro' name from the pre-war and post-war woodies, and several Bakelite sets.

The dials were beautifully designed and made whatever the model, and the T105 was no exception.

A couple of before/after pics of mine are attached.

The extent to which the paint had faded over time will be evident in the first pic. For the re-spray, I colour matched the aerosol to the original brighter blue.
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Old 6th Feb 2018, 7:41 pm   #4
DigitalNoMore
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Default Re: Pilot Little Maestro T105

That's an excellent paint job David.
I was fortunate in that the case paint was in very good condition.

Interesting points you made about the real terms original cost of the T105. Particularly when it was probably sold as a low end set at the time.

Jerry
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