Another Pilot Little Maestro restoration project. - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 24th Nov 2021, 12:49 pm

Arrived yesterday, this rather untidy Little Maestro radio set.
The attachments show the set will need a fair amount of work to restore it to an usable condition.
About the receiver: valve line-up is 6A7G, 6K7G, 6Q7G and 25A6G. The HT rectifier should be a 25Z6G or 25Z6G. However, this set has been fitted with an UX base Brimar 1D6.
The heater chain will be supplied through a capacitive dropper, the value has been determined to be 4.2mfd.
The loudspeaker is the type with a field coil which will also take care of the HT smoothing.
First task is remove that mains transformer. Other uses can be found for it.

DFWB.

Radio Scotland · 24th Nov 2021, 12:58 pm

Hey you can't start another maestro restoration thread till mine is finished

She's rough, Very rough!!. My rectifier valve is a 25Z4G. i'll find out soon whether it works or not, Be interesting to see how you get on with this set,

Cheers
Jay

FERNSEH · 24th Nov 2021, 2:11 pm

Hi Jay,
I'm sure your Little Maestro project will be completed by the time my restoration is finished. The difficult part of the restoration will be the cabinet.
Not too concerned about the electronics.

DFWB.

Radio Scotland · 24th Nov 2021, 3:03 pm

Quote:

Originally Posted by FERNSEH

Hi Jay,
I'm sure your Little Maestro project will be completed by the time my restoration is finished.

DFWB.

I hope your right, I'll be plugging it in later today

Jay

bobhowe · 24th Nov 2021, 7:23 pm

Hi David has the cabinet got any wee beasties

agardiner · 24th Nov 2021, 8:03 pm

Wow - you have taken on a beast of a restore there. Look forward to following your progress.

Radio Scotland · 24th Nov 2021, 8:11 pm

Quote:

Originally Posted by agardiner

Wow - you have taken on a beast of a restore there. Look forward to following your progress.

He hasn't half, Makes mine look brand new

FERNSEH · 24th Nov 2021, 9:52 pm

I knew what I was letting myself in for with this one. It's very rusty but still restorable.
All the components will have to be removed from the chassis to do a proper de-rusting job. Thankfully, it's a very simple receiver. Low component count.
Then there's the tatty cabinet to attend to. At least it's worm free.
The mains transformer has been removed from the chassis. It will be tested to find out if it will be any use in future projects.
The attachments show just how awful the condition of the chassis is in.
Not too bad underneath though.

DFWB.

Radio Scotland · 24th Nov 2021, 10:45 pm

The chassis should clean up ok, Not so sure about the tuning dial plate, Should keep you occupied for a wee while anyhow, Look forward to seeing how it progresses.

P.S Did you salvage it from the titanic ?

Cheers
Jay

FERNSEH · 24th Nov 2021, 11:10 pm

Sourced from eBay. Strangely, I was the only bidder.

DFWB.

murphyv310 · 24th Nov 2021, 11:27 pm

Hi David.
I'm really surprised why no one else would give it a go.
Like you I prefer rusty wrecks. My PYE V4 TV would fail its TV MOT if there was such a tester, its very rusty, the HMV 2807 was bad too. Bourne out by virtually every cap shot including low value Pf values. Corroded resistor leads and rust everywhere. Now works a treat and awaiting a watchable tube.
A Ferranti 146 I acquired came from a barn and you want to have seen the state it was in, mind boggling.
Good luck with the restore.

FERNSEH · 25th Nov 2021, 11:40 am

Quote:

Originally Posted by bobhowe

Hi David has the cabinet got any wee beasties

Have found a few holes in the top of the now detached to panel.

DFWB.

FERNSEH · 25th Nov 2021, 10:47 pm

The cabinet received some attention today. Despite this being a low cost set the detailing of the veneers is quite remarkable.
The top is properly book matched.
A Radiospares output transformer was fitted at one time long ago.
The 1D6 rectifier valve will be replaced with an octal base 25Z4G or 25Z6G. The Osram U31 can be used as an alternative.
For a temporary replacement a PY32 or PY33 can be used, 29volt heater.

DFWB.

Radio Scotland · 25th Nov 2021, 11:10 pm

Quote:

Originally Posted by FERNSEH

The cabinet received some attention today. Despite this being a low cost set the detailing of the veneers is quite remarkable.
The top is properly book matched.
A Radiospares output transformer was fitted at one time long ago.
The 1D6 rectifier valve will be replaced with an octal base 25Z4G or 25Z6G. The Osram U31 can be used as an alternative.
For a temporary replacement a PY32 or PY33 can be used, 29volt heater.

DFWB.

Good to know the U31 Can be used as a replacement, Theres a few NOS ones online, And i thought the transformer didn't look original, Look forward to more updates on the auld lady

Jay

FERNSEH · 26th Nov 2021, 1:34 pm

Details of alternative HT rectifier valves for the Little Maestro.
Marconi-Osram U31: https://www.radiomuseum.org/tubes/tube_u31.html Note the circuit includes a barretter to serve as the voltage dropper.
Mullard PY32 or PY33: https://www.radiomuseum.org/tubes/tube_py32.html
Early PY32 valves with the ST shape bulb had two separate anodes.
All the tubular shape valves have a single anode.

DFWB.

FERNSEH · 27th Nov 2021, 11:31 am

Yesterday, a number of tests were performed on the chassis.
the overly large HT smoothing capacitor has values of 16 + 24mfd and is certainly the type used in the Bush DAC90.
The output transformer has a primary resistance of 560ohms and secondary resistance of 1.8ohms. The loudspeaker speech coil resistance is 4.2ohms.
The loudspeaker field coil has a low? resistance of 330ohms.
The UX type valveholder will be replaced with an octal type which will allow the fitment of different types of rectifier valve. 25Z4G, 26Z6G etc.
The fact that this set employs the 6A8G heptode as the frequency changer indicates that the set is the series 1 pre-war model.
Post-war models employ the 6K8G triode-hexode as the frequency changer.
The cabinet received some attention. Cabinet top is now glued into position.

DFWB

FERNSEH · 2nd Dec 2021, 11:38 am

For the time being the UX base 1D6 HT rectifier valve will remain in place.
Yesterday, almost all the waxie capacitors were tested and as expected all were found to be useless. Temporary replacements fitted. A smaller HT smoothing capacitor fitted in order to make space for the heater chain voltage dropper capacitor.
Resistors found to be within tolerance, well only just. +/- 20% was the norm at the time the set was made. Resistance between the HT rail and chassis is >1Megohms.
The 4mfd motor start capacitor connected between the top of the heater chain and mains live. The single pole on-off switch has a contact resistance of 1.3 ohms. Attach a mains lead with plug to the chassis.
Ready to apply full mains. Switch on. After the valves have warmed the big surprise is that the set actually works. Peaking up the IF transformers improved matters further.
Having proved the set is a viable proposition work can continue tidying up the chassis metalwork.

DFWB.

Station X · 2nd Dec 2021, 11:46 am

Well done. Only 17 posts in the thread and the set is working!

Radio Scotland · 2nd Dec 2021, 6:19 pm

Quote:

Originally Posted by Station X

Well done. Only 17 posts in the thread and the set is working!

Wish i could say the same

bobhowe · 2nd Dec 2021, 7:23 pm

Hi David set looks great if it was mine I would leave the chassis's as is as it has took over 50 years to look like that just a thought kind regards Bob

24th Nov 2021, 12:49 pm	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Another Pilot Little Maestro restoration project. Arrived yesterday, this rather untidy Little Maestro radio set. The attachments show the set will need a fair amount of work to restore it to an usable condition. About the receiver: valve line-up is 6A7G, 6K7G, 6Q7G and 25A6G. The HT rectifier should be a 25Z6G or 25Z6G. However, this set has been fitted with an UX base Brimar 1D6. The heater chain will be supplied through a capacitive dropper, the value has been determined to be 4.2mfd. The loudspeaker is the type with a field coil which will also take care of the HT smoothing. First task is remove that mains transformer. Other uses can be found for it. DFWB. Attached Thumbnails

24th Nov 2021, 12:58 pm	#2
Radio Scotland Heptode Join Date: Jul 2020 Location: Larkhall, South Lanarkshire, Scotland. Posts: 671	Re: Another Pilot Little Maestro restoration project. Hey you can't start another maestro restoration thread till mine is finished She's rough, Very rough!!. My rectifier valve is a 25Z4G. i'll find out soon whether it works or not, Be interesting to see how you get on with this set, Cheers Jay __________________ Help!! I've been electrocuted by a glass thing that glows

24th Nov 2021, 2:11 pm	#3
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. Hi Jay, I'm sure your Little Maestro project will be completed by the time my restoration is finished. The difficult part of the restoration will be the cabinet. Not too concerned about the electronics. DFWB.

24th Nov 2021, 7:23 pm	#5
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Another Pilot Little Maestro restoration project. Hi David has the cabinet got any wee beasties __________________ Kind regards, Bob.

24th Nov 2021, 8:03 pm	#6
agardiner Octode Join Date: Sep 2020 Location: Thetford, Norfolk, UK. Posts: 1,741	Re: Another Pilot Little Maestro restoration project. Wow - you have taken on a beast of a restore there. Look forward to following your progress.

24th Nov 2021, 9:52 pm	#8
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. I knew what I was letting myself in for with this one. It's very rusty but still restorable. All the components will have to be removed from the chassis to do a proper de-rusting job. Thankfully, it's a very simple receiver. Low component count. Then there's the tatty cabinet to attend to. At least it's worm free. The mains transformer has been removed from the chassis. It will be tested to find out if it will be any use in future projects. The attachments show just how awful the condition of the chassis is in. Not too bad underneath though. DFWB. Attached Thumbnails Last edited by FERNSEH; 24th Nov 2021 at 9:57 pm.

24th Nov 2021, 10:45 pm	#9
Radio Scotland Heptode Join Date: Jul 2020 Location: Larkhall, South Lanarkshire, Scotland. Posts: 671	Re: Another Pilot Little Maestro restoration project. The chassis should clean up ok, Not so sure about the tuning dial plate, Should keep you occupied for a wee while anyhow, Look forward to seeing how it progresses. P.S Did you salvage it from the titanic ? Cheers Jay __________________ Help!! I've been electrocuted by a glass thing that glows

24th Nov 2021, 11:10 pm	#10
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. Sourced from eBay. Strangely, I was the only bidder. DFWB.

24th Nov 2021, 11:27 pm	#11
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Another Pilot Little Maestro restoration project. Hi David. I'm really surprised why no one else would give it a go. Like you I prefer rusty wrecks. My PYE V4 TV would fail its TV MOT if there was such a tester, its very rusty, the HMV 2807 was bad too. Bourne out by virtually every cap shot including low value Pf values. Corroded resistor leads and rust everywhere. Now works a treat and awaiting a watchable tube. A Ferranti 146 I acquired came from a barn and you want to have seen the state it was in, mind boggling. Good luck with the restore. __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

25th Nov 2021, 10:47 pm	#13
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. The cabinet received some attention today. Despite this being a low cost set the detailing of the veneers is quite remarkable. The top is properly book matched. A Radiospares output transformer was fitted at one time long ago. The 1D6 rectifier valve will be replaced with an octal base 25Z4G or 25Z6G. The Osram U31 can be used as an alternative. For a temporary replacement a PY32 or PY33 can be used, 29volt heater. DFWB. Attached Thumbnails

26th Nov 2021, 1:34 pm	#15
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. Details of alternative HT rectifier valves for the Little Maestro. Marconi-Osram U31: https://www.radiomuseum.org/tubes/tube_u31.html Note the circuit includes a barretter to serve as the voltage dropper. Mullard PY32 or PY33: https://www.radiomuseum.org/tubes/tube_py32.html Early PY32 valves with the ST shape bulb had two separate anodes. All the tubular shape valves have a single anode. DFWB.

27th Nov 2021, 11:31 am	#16
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. Yesterday, a number of tests were performed on the chassis. the overly large HT smoothing capacitor has values of 16 + 24mfd and is certainly the type used in the Bush DAC90. The output transformer has a primary resistance of 560ohms and secondary resistance of 1.8ohms. The loudspeaker speech coil resistance is 4.2ohms. The loudspeaker field coil has a low? resistance of 330ohms. The UX type valveholder will be replaced with an octal type which will allow the fitment of different types of rectifier valve. 25Z4G, 26Z6G etc. The fact that this set employs the 6A8G heptode as the frequency changer indicates that the set is the series 1 pre-war model. Post-war models employ the 6K8G triode-hexode as the frequency changer. The cabinet received some attention. Cabinet top is now glued into position. DFWB Attached Thumbnails

2nd Dec 2021, 11:38 am	#17
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Another Pilot Little Maestro restoration project. For the time being the UX base 1D6 HT rectifier valve will remain in place. Yesterday, almost all the waxie capacitors were tested and as expected all were found to be useless. Temporary replacements fitted. A smaller HT smoothing capacitor fitted in order to make space for the heater chain voltage dropper capacitor. Resistors found to be within tolerance, well only just. +/- 20% was the norm at the time the set was made. Resistance between the HT rail and chassis is >1Megohms. The 4mfd motor start capacitor connected between the top of the heater chain and mains live. The single pole on-off switch has a contact resistance of 1.3 ohms. Attach a mains lead with plug to the chassis. Ready to apply full mains. Switch on. After the valves have warmed the big surprise is that the set actually works. Peaking up the IF transformers improved matters further. Having proved the set is a viable proposition work can continue tidying up the chassis metalwork. DFWB. Attached Thumbnails

2nd Dec 2021, 11:46 am	#18
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Another Pilot Little Maestro restoration project. Well done. Only 17 posts in the thread and the set is working! __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

2nd Dec 2021, 7:23 pm	#20
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Another Pilot Little Maestro restoration project. Hi David set looks great if it was mine I would leave the chassis's as is as it has took over 50 years to look like that just a thought kind regards Bob __________________ Kind regards, Bob.