Little Maestro (Bakelite) back panel info please

[David G4EBT]

I have a Little Maestro Bakelite radio which I picked up at the Nov 2015 Golborne Swapmeet and hope to get around to restoring sometime this year. It doesn't have a back and initially I'd appreciate some information about the slot dimensions. I do have a picture of what the back should look like, which I've attached below. I've also attached a sketch showing what slot dimensions I need to enable me to make a back panel. If anyone has a Little Maestro with this cabinet type and could kindly let me know that this missing dimension on my sketch are, I'd be most grateful. A picture including the text on the panel would be an added bonus.

From the sets appearance, initially I thought it was the Post-War AC only version (Trader Sheet 809). However, on closer examination the rear chassis apron is stamped AC/DC so there's no main transformer. That said, it isn't pre-war because the dial shows the Light Programme on 1,500M Long Wave and that wasn't introduced until July 29 1945. However, there is no Third Programme on the dial, (which went on air on 29 Sept 1946), so that pretty much pins the set down to 1945. It also has a permanent magnet speaker - not a mains energised one.

It seems to have been 'got at' in that there's a multi section dropper, with none of the taps used, and with a total resistance of 390R, mounted on what appears to be a DIY aluminium bracket, quite neatly done, above the speaker.

The valves, as found are:

V1 6K8G
V2 6K7G
V3 6Q7G
V4 VT201A (Equiv 25L6GT)
V5 25Z4

All of those valves have 0.3A heaters. V1, V2, V3 are 6.3V, V4 & V5 are 25V each, so the total heater chain amounts to 68.9V. The 25Z4 has an indirectly heated cathode, so can share the heater chain with the other four valves. Looking at the Radio Servicing Data - which outlines the ten models in the Little Maestro range - the valve line-up and general layout seems to correspond to the post-war AC/DC model, ('Model 2'), though that had a mains energised speaker and line cord dropper, whereas the speaker in this set is PM, looks factory fitted, and there's a 5A two-pin plug on the ends of the mains lead (non-original).

No doubt when I have a closer look at the DIY dropper arrangement, things will come clearer - leastways, I hope so!

The first pic is of a back for the same cabinet style. Second pic shows the two dimensions I'm seeking for the slots in the back, which I've referred to as 'Dimension A' & Dimension B': Firstly, the length of the slots, and secondly, the distance between the top of one slot, and the top of the slot in the next row down. The third pic is an end view of the 'DIY' aluminium support shield, with the end stud of the dropper. The fourth pic shows the dropper from the rear of the set, and the last pic is of the underside of the chassis as found. Clearly, scope for a jolly good fettle up!

[Gridiron]

Hello David,
I've had a look at the set I've got, the slot length is 28 mm, the other dimension 39.5 mm. I've attached a photo of the back showing the legends on it.
Best Regards,
Mike (Gridiron).

[David G4EBT]

Thanks for taking the trouble to take the pic and measure the slots Mike - that's very helpful!

The lengths of slots used by various manufacturers that I've encountered to date have ranged from 18, 25 & 28mm, and the spacing from one row to the next row down have varied from 35, 38, 40 & 42. Obviously when there are several rows of slots it can make an appreciable difference to the overall appearance if the length and spacing aren't as per the original. The slot width and horizontal spacing between slots seems to be pretty much standard, with 6mm slots at 13mm centres. (I guess that's 1/4" slots at 1/2" intervals in 'old money').

(I see that there's a little 'bay' at the LH end of the back to stow the 'throw-out' aerial - or is it a 'window' of clear plastic? The wire aerial lead seems to emerge from a hollow rivet to the left of the 'window).

I'll post a pic when I've made a replica back.

[kenneth]

A few pics, Ken.

[David G4EBT]

Thanks Ken - really helpful info and pics to add to Mike's.

Is the slot for the 'throw out' aerial please, and what are the 'flaps' in the slot made of?

[kenneth]

David, I do not know a lot about the Little Maestro - my example has been heavily modded and remains in my pending tray! I can think of no other purpose for the slot and its attached pouch other than for use as storage for the fixed wire aerial. Mike's pic shows the wire aerial being fed through one of the pouches six rivet holes - my pic below shows that that hole was not intended to hold a rivet so its proper purpose was surely the exit hole for the fixed wire aerial. The pouch is made from a stiff, crisp thin (guessing about .3mm) material which must obviously be heat-proof but have no idea what. Sorry I cannot be more precise. Ken.

[David G4EBT]

Thanks Ken - that's really helpful.

It confirms what is shown in pic one of my post, which is an image I found which shows the throw out aerial wound on a card and pushed into the slot in the back. Your picture confirms that it's not simply a slot, but a pouch. The Little Maestro 'woodie' - one of which I restored a little while ago - has a throw out aerial stowed in the top in two wooden slides. When I got the set the aerial was missing and the back was damaged, but enough of it was left to enable me to use as a template, so I made a new back and an aerial for it. I've attached a few pics of the old and new back, and the aerial that I made, which you'll see tucked into the LH slot at the back.

With the help and the pics from you and Mike, I've been able to draw an outline for a replica back, which is below, so as soon as I'm able I'll set up my router and knock up a back.

Many thanks to both you and Mike for pointing me in the right direction.

[Gridiron]

David,
I have had another look at the back of the set I have, the pouch material appears to be made of something like cartridge paper or the type of paper sometimes used for packaging, I would think the 6K8 valve next to it does not get very hot so it wouldn't need to be very heat resistant.
Mike.

[David G4EBT]

Thanks Mike.

It looks rather like the thick card that I've occasionally seen on transformer bobbins, such as those made by Elstone. Also, rather like the tough paper that suspension files are made of, but the aerial pocket is thicker - more like card. I've got some thin Paxolin, so might make up a 'box', open at the front end. I managed to make a new back panel yesterday, which I've carefully trimmed to accurately fit the cabinet. I've drawn round the outline in case it's of use to anyone else with a 'backless' Bakelite Little Maestro. Just need to make and fit the aerial pocket, paint the panel matt brown and stick on a label that I've made.

Then I'll turn my attention to the electronics, which at the moment are a bit puzzling!

The Radio Servicing data lists ten variations in the Little Maestro series, some of which use an auto transformer - others had a line cord dropper. Some had mains energised speakers with a field coil - others, such as mine, had a PM speaker. As far as I can tell at this stage, mine seems to be the 'Type 2', - PM speaker and originally a line cord dropper. I know some restorers have used a capacitive dropper, which is perhaps the route I may have to take, but at the moment - not having closely examined the set - it only seems to have a (non-original) 390R wire-wound dropper I mentioned in my first post, which I'd estimate from its appearance is capable of dissipating no more than 15 - 20 Watts. However, given that the heater chain is rated at 0.3 Amps, and drops 69V, that leaves another 171V to drop for the heater chain, tapped off for the HT and dial bulb. 171V at 0.3A = 51 Watts, so it would need a hefty wire-wound resistor, well beyond the capability of the existing one, and would generate a lot of heat in a small cabinet.

I'll know a bit more when I start to look closer at the chassis.

Thanks once more for your help Mike, and Ken too. When I've made the aerial pocket and finished the back, I'll post a pic.

(The factory-finished cream on Bakelite cabinet is going to need a re-spray too - I'd prefer that to taking it back to Brown).

[David G4EBT]

Just a little update on this thread.

I did finish the back - I made a little aerial pocket from leatherette turned inside out. I fitted it to the back with 6BA screws, and made a little throw-out aerial along the lines of the 'woodie' Maestro that I restored a while ago. Won't get round to restoring the radio for a little while as it needs rather more than simply changing a few caps. Once more, I'd like to reiterate my thanks to Mike and Ken for their help in enabling me to get on with the back.

Yet another radio restoration of mine that's 'work in progress', though to use the term 'progress' is perhaps stretching it a bit!

Oh well, in three weeks, the nights get longer and the days shorter, so looking ahead, maybe it can be a 'winter project'?

[kenneth]

Got to give you 10+ out of 10 for that David. Super job. Ken.

[David G4EBT]

Thanks for our kind words Ken.

Really, I posted the pics so you'd know that the trouble you and Mike went to in providing info and pics, did produce an end result.