Pilot little maestro 444 mains dropper bother - UK Vintage Radio Repair and Restoration Discussion Forum

trabant · 12th Sep 2019, 7:54 pm

So as per usual went out to buy a DAC90a came home with that and a 38/39 pilot little maestro 444 now aware that these sets originally used the mains lead as the resistance to drop the voltage to the set obviously this has long since gone and been replaced with a dirty great big dropper resistor haphazardly bodged on to the chassis. Now I have a very nice Stewart Warner c151 obviously an American set and therefore US voltage this plugs straight in to our mains and uses a motor start capacitor as a dropper for the heaters can you do that to this pilot and if so how ? As the current set up is scorching the case .

Ed_Dinning · 12th Sep 2019, 7:59 pm

Hi Trabant, have a look on the forum and you should find a reference to capacitive droppers and how to calculate them. Typical values are in the 2 to 4uF range and motor run or X class caps work fine.
There has been discussions about how they will not work correctly, or damage your set if they fail; however, in my experience they present no problems.

Ed

Ambientnoise · 12th Sep 2019, 8:05 pm

Is this link any help (scroll down to near the bottom for a capacitive dropper in a little maestro)

http://www.pasttimesradio.co.uk/arti..._projects.html

If your set is different, the values will need changing.

https://www.vintage-radio.com/repair...per-calcs.html

Ken

trabant · 12th Sep 2019, 8:34 pm

Oh that's exactly what I needed Ed and Ken thanks very much

Sideband · 12th Sep 2019, 8:57 pm

Just for information, I replaced the failed dropper in my Pilot Little Maestro model 10 using a capacitor (2.5uF) retrieved from an old fluorescent light fitting. I trimmed the value by fitting a 0.1uF X class capacitor in parallel with it. It's been working for about 10 years with no problems at all.

Ideally you should use a motor run capacitor since these are designed for continuous use and usually rated at around 400V AC. You can trim the value by connecting an X class cap in parallel if necessary. X class caps also seem to work fine in this position....at least I've never had a problem with them.

The set will run much cooler with a capacitive dropper.

12th Sep 2019, 7:54 pm	#1
trabant Retired Dormant Member Join Date: Mar 2010 Location: Carlisle, UK. Posts: 164	Pilot little maestro 444 mains dropper bother So as per usual went out to buy a DAC90a came home with that and a 38/39 pilot little maestro 444 now aware that these sets originally used the mains lead as the resistance to drop the voltage to the set obviously this has long since gone and been replaced with a dirty great big dropper resistor haphazardly bodged on to the chassis. Now I have a very nice Stewart Warner c151 obviously an American set and therefore US voltage this plugs straight in to our mains and uses a motor start capacitor as a dropper for the heaters can you do that to this pilot and if so how ? As the current set up is scorching the case .

12th Sep 2019, 7:59 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Pilot little maestro 444 mains dropper bother Hi Trabant, have a look on the forum and you should find a reference to capacitive droppers and how to calculate them. Typical values are in the 2 to 4uF range and motor run or X class caps work fine. There has been discussions about how they will not work correctly, or damage your set if they fail; however, in my experience they present no problems. Ed

12th Sep 2019, 8:05 pm	#3
Ambientnoise Heptode Join Date: Feb 2006 Location: Marlborough, Wiltshire, UK. Posts: 915	Re: Pilot little maestro 444 mains dropper bother Is this link any help (scroll down to near the bottom for a capacitive dropper in a little maestro) http://www.pasttimesradio.co.uk/arti..._projects.html If your set is different, the values will need changing. https://www.vintage-radio.com/repair...per-calcs.html Ken

12th Sep 2019, 8:34 pm	#4
trabant Retired Dormant Member Join Date: Mar 2010 Location: Carlisle, UK. Posts: 164	Re: Pilot little maestro 444 mains dropper bother Oh that's exactly what I needed Ed and Ken thanks very much

12th Sep 2019, 8:57 pm	#5
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,567	Re: Pilot little maestro 444 mains dropper bother Just for information, I replaced the failed dropper in my Pilot Little Maestro model 10 using a capacitor (2.5uF) retrieved from an old fluorescent light fitting. I trimmed the value by fitting a 0.1uF X class capacitor in parallel with it. It's been working for about 10 years with no problems at all. Ideally you should use a motor run capacitor since these are designed for continuous use and usually rated at around 400V AC. You can trim the value by connecting an X class cap in parallel if necessary. X class caps also seem to work fine in this position....at least I've never had a problem with them. The set will run much cooler with a capacitive dropper. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....