UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

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

View Poll Results: Will the radio work when turned on at 4PM?
YES 2 10.00%
NO 18 90.00%
Voters: 20. You may not vote on this poll

Closed Thread
 
Thread Tools
Old 14th Nov 2021, 5:49 pm   #161
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by FERNSEH View Post
Checked the AC voltages in my Little Maestro, Mains voltage today is 238V.
The voltage at the top of the heater chain is 65V, should 70volts so the valves are slightly under-run. The voltage measured across the heater dropper capacitor is 228V.
Nevertheless, the set is working perfectly and is receiving all five of the local medium waveband stations with no aerial. With 10 feet of wire the set is very lively.
The 4 microfarad RS Components capacitor has the stock number 388-7686.
Correction to the valve line-up: the output valve is a 25A6G and the rectifier an Osram U31.
Checked the value of an unused new stock RS capacitor and the figure is 3.94 microfarads.

DFWB.
Thanks for that, I get the 5 valve heaters and dial lamp coming out at 75 volts, Unless i'm missing something.

Frustrating having to wait on another dropper cap coming in the post Out of desperation i paid 50p extra for first class postage

Cheers
Jay
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 14th Nov 2021, 6:30 pm   #162
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: Pilot Little Maestro restoration project.

Hi Jay, if you can achieve 75volts at the top of the heater chain, then everything will be in order. In fact spot on if the dial light is a 6.3 volt bulb.
Assume the valve line-up is 6A8G alt 6K8G, 6K7G alt 6U7G, 6Q7G, 25A6 or alt 25L6 and 25Z6.
DFWB.

Last edited by FERNSEH; 14th Nov 2021 at 6:39 pm.
FERNSEH is offline  
Old 14th Nov 2021, 6:34 pm   #163
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by FERNSEH View Post
Hi Jay, if you have 75volts at the top of the heater chain, then everything is in order. In fact spot on if the dial light is a 6.3 volt bulb.

DFWB.
I don't have it yet, But adding the voltage of 5 x valves + dial lamp = 75v

If i get close i'll be happy


Cheers
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 14th Nov 2021, 6:56 pm   #164
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
Default Re: Pilot Little Maestro restoration project.

In reality, a few volts either way for the heater supply won't make a lot of difference. Remember when these sets were built, they didn't have a mains voltage tap and were rated 200 - 250V without adjustment. At the low end of mains, the valves would have been under run. At 240 - 250V, they would have been running normally. it's likely that for 90% of their use, the valves would have been slightly under run.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman.....
Sideband is offline  
Old 14th Nov 2021, 7:32 pm   #165
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Sideband View Post
In reality, a few volts either way for the heater supply won't make a lot of difference. Remember when these sets were built, they didn't have a mains voltage tap and were rated 200 - 250V without adjustment. At the low end of mains, the valves would have been under run. At 240 - 250V, they would have been running normally. it's likely that for 90% of their use, the valves would have been slightly under run.
Yeah i suppose running them slightly under voltage will prolong the life of the filaments.


Jay
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 14th Nov 2021, 7:57 pm   #166
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Does anybody think this will actually work first time when the heaters & HT Supply is sorted out ?
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 14th Nov 2021, 8:59 pm   #167
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,171
Default Re: Pilot Little Maestro restoration project.

Probably a very high chance of success; worst case it will only damage 1 valve but without one of us testing it we have no way of knowing.

You could try running on a lamp limiter or variac at reduced voltage.
Measure heater string volts and then volts into set. They should be in the proportion of
75/240 of whatever voltage you are applying

Ed
Ed_Dinning is offline  
Old 14th Nov 2021, 9:09 pm   #168
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Ed_Dinning View Post
Probably a very high chance of success; worst case it will only damage 1 valve but without one of us testing it we have no way of knowing.

You could try running on a lamp limiter
Ed
Thats the plan Ed if i can nick an incandescent light bulb from somewhere, Hardly see them these days, Maybe a 100 watt bulb ?

If the valves are good and theres no coils/inductors open or shorted, Then it should sing again.

Just found a red 60w bayonet bulb, The type for a log effect fire and a 100w screw in, But no socket for it.

Jay
__________________
Help!! I've been electrocuted by a glass thing that glows

Last edited by Radio Scotland; 14th Nov 2021 at 9:36 pm. Reason: Additional info
Radio Scotland is offline  
Old 14th Nov 2021, 9:45 pm   #169
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
Default Re: Pilot Little Maestro restoration project.

I've just been in the 'mancave' and tried the Pilot Model 10 that I converted to capacitor dropper around 12 years ago. All still good so I thought I'd show you how I did mine. I used a capacitor from an old florescent fitting which was a 2.6uF at 400Vac which was pretty much spot on for the value I needed. When I measured it however is was slightly low at 2.4uF. When fitted, the radio worked well but was a tad low on heater voltage so I fitted a couple of 0.1uF caps in parallel and put them in parallel with the 2.6uF to bring the value up and I was happy with the result. I subsequently replaced the two 0.1uF caps with a single 0.22uF cap at 300Vac which fitted much more neatly into the available space.

I used the original dropper mounting cage with some shrink-sleeving which made a snug fit into the space. Well it's been OK for the last 12 years with moderate use.

The last one just shows the mains voltage at the time which is a tad under 240V.
Attached Thumbnails
Click image for larger version

Name:	js1024_100_0465.jpg
Views:	74
Size:	85.6 KB
ID:	245792   Click image for larger version

Name:	js1024_100_0466.jpg
Views:	77
Size:	111.1 KB
ID:	245793   Click image for larger version

Name:	js1024_100_0467.jpg
Views:	64
Size:	91.9 KB
ID:	245794   Click image for larger version

Name:	js1024_100_0469.jpg
Views:	68
Size:	108.5 KB
ID:	245795  
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman.....

Last edited by Sideband; 14th Nov 2021 at 9:55 pm.
Sideband is offline  
Old 14th Nov 2021, 9:59 pm   #170
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Sideband View Post
I've just been in the 'mancave' and tried the Pilot Model 10 that I converted to capacitor dropper around 12 years ago. All still good so I thought I'd show you how I did mine. I used a capacitor from an old florescent fitting which was a 2.6uF at 300Vac which was pretty much spot on for the value I needed. When I measured it however is was slightly low at 2.4uF. When fitted, the radio worked well but was a tad low on heater voltage so I fitted a couple of 0.1uF caps in parallel and put them in parallel with the 2.6uF to bring the value up and I was happy with the result. I subsequently replaced the two 0.1uF caps with a single 0.22uF cap at 300Vac which fitted much more neatly into the available space.

I used the original dropper mounting cage with some shrink-sleeving which made a snug fit into the space. Well it's been OK for the last 12 years with moderate use.

The last one just shows the mains voltage at the time which is a tad under 240V.
Cheers sideband, Nice job The pilot i'm working on is a keeper, Always wanted a valve radio for the nice warm sound from them, But didn't wanna pay daft online prices, Nor did i want one the size of a headstone, So when i spotted the little pilot i had to have it.

Like i say iv'e never worked on a valve set before or really done any restoration work on a radio, But learning plenty from this thread,


Does anybody know the working wattage of this radio ? I'm thinking around 40 watts.


Cheers
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 14th Nov 2021, 11:12 pm   #171
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,548
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Radio Scotland View Post

Does anybody know the working wattage of this radio ? I'm thinking around 40 watts.


Cheers
Well unless it's stated in any of the service literature or (sometimes) printed on the back of the radio, then 40W is a fair guess. Your set uses 300mA valve heaters whereas mine uses 150mA heaters. According to my power meter mine is running at around 28W so I suppose if you were to double that to 56W it probably won't be far out.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman.....
Sideband is offline  
Old 14th Nov 2021, 11:17 pm   #172
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Sideband View Post
Quote:
Originally Posted by Radio Scotland View Post

Does anybody know the working wattage of this radio ? I'm thinking around 40 watts.


Cheers
Well unless it's stated in any of the service literature or (sometimes) printed on the back of the radio, then 40W is a fair guess. Your set uses 300mA valve heaters whereas mine uses 150mA heaters. According to my power meter mine is running at around 28W so I suppose if you were to double that to 56W it probably won't be far out.
Cheers. Can't find any reference in the service info or on the radio itself, I reckon my 100w dim bulb tester should be ok,


Jay
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 2:51 pm   #173
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Trying to find small enough bolts to mount the HT Resistor isn't easy

Its a job for the dremel
Attached Thumbnails
Click image for larger version

Name:	IMAG0063.jpg
Views:	56
Size:	29.7 KB
ID:	245868  
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 5:50 pm   #174
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

''Bodged in''
Attached Thumbnails
Click image for larger version

Name:	IMAG0065.jpg
Views:	64
Size:	65.7 KB
ID:	245872  
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 7:26 pm   #175
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

I'm confused. In the pic below is the way the rectifier socket is wired, White wire is the anodes, Piece of solder is the cathodes. I Have a 25Z4G Rectifier, Radio calls for a 25Z6G.

But the socket doesn't looked as if its wired for either of them, I'm probably missing the obvious, Been a long day.


Jay
Attached Thumbnails
Click image for larger version

Name:	Screenshot from 2021-11-15 17-52-13.jpg
Views:	49
Size:	82.3 KB
ID:	245891   Click image for larger version

Name:	Screenshot 2021-11-15 at 18-00-23 25Z6, Tube 25Z6; Röhre 25Z6 ID1993, High-vacuum Rectifier.png
Views:	37
Size:	2.4 KB
ID:	245892   Click image for larger version

Name:	Screenshot 2021-11-15 at 18-00-57 25Z4, Tube 25Z4; Röhre 25Z4 ID5707, Half-Wave Vacuum Rectifi.png
Views:	35
Size:	5.4 KB
ID:	245893  
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 7:35 pm   #176
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Pilot Little Maestro restoration project.

The socket in the photo is wired for either so far as I can make out, 3&5 are connected together (anode(s)) and 8&4 are connected together (cathode(s)) Numbered anticlockwise in the socket photo starting with number 1 which is the first to the right of the keyway for the spigot, the first to the left of the keyway being number 8.

Lawrence.

Last edited by ms660; 15th Nov 2021 at 7:46 pm. Reason: extra info
ms660 is offline  
Old 15th Nov 2021, 7:48 pm   #177
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by ms660 View Post
The socket in the photo is wired for either so far as I can make out, 3&5 are connected together (anode(s)) and 8&4 are connected together (cathode(s)) Numbered anticlockwise in the socket photo starting with number 1 which is the first to the right of the keyway for the spigot, the first to the left of the keyway being number 8.

Lawrence.
Yup. The valve diagrams are a bottom view, And thats what was throwing me, Not used to working with valves, Better safe than sorry,,


Thanks
Jay
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 8:08 pm   #178
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Pilot Little Maestro restoration project.

Some of the side contact valves were numbered anticlockwise as viewed from underneath, eg:

https://frank.pocnet.net/sheets/030/e/ECH3.pdf

Lawrence.
ms660 is offline  
Old 15th Nov 2021, 8:41 pm   #179
Radio Scotland
Heptode
 
Radio Scotland's Avatar
 
Join Date: Jul 2020
Location: Larkhall, South Lanarkshire, Scotland.
Posts: 671
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by ms660 View Post
Some of the side contact valves were numbered anticlockwise as viewed from underneath, eg:

https://frank.pocnet.net/sheets/030/e/ECH3.pdf

Lawrence.
Cheers lawrence, Learning more each day.

I have a metal temperature probe on my DMM,Was wondering if i could use it to monitor the temp of the HT resistor ? Keeping in mind chassis is hooked to neutral..


Jay
__________________
Help!! I've been electrocuted by a glass thing that glows
Radio Scotland is offline  
Old 15th Nov 2021, 8:51 pm   #180
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Pilot Little Maestro restoration project.

Quote:
Originally Posted by Radio Scotland View Post
I have a metal temperature probe on my DMM,Was wondering if i could use it to monitor the temp of the HT resistor ? Keeping in mind chassis is hooked to neutral..
I've no idea, DMM gizmo's were after my time, 'twas an Avo and spit back in my day.

Lawrence.
ms660 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:32 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.