Pilot Little Maestro. AC/DC.

[longneck90]

Hello to everyone. I had a bit of a misfortune last week, when I put this radio up on the bench/worktop to have a look at it, and... it promptly fell off, making bits of the cabinet and 6K8G as well. My problem is; This chassis has a selenium rectifier and, while I have accessed circuit diagrams of the 'Little Maestro' and the 'Mighty Maestro', none of these circuit diagrams cover a chassis with a selenium rectifier. While the workings of the selenium rectifier may not pose any great problem, the wiring/connections around valve 1 (6K8G) does present a problem, as it seems different from what is displayed in any of the circuit diagrams that I have. I was therefore wondering, and hoping, that some kind Forum Member might have a circuit diagram of Pilot Little Maestro, whose chassis included a selenium rectifier. Of course, any costs incurred in this transaction will be fully refunded. All the best. John.

[Cobaltblue]

I think that's been modified and not by Pilot.

It looks as if a transformer has been fitted where the 25Z4 was fitted.

This allows the use of a 6V6 instead of the 25A6 and the mains dropper lead can be replaced by a standard lead.

The Metal Rectifier replaces the 25Z4 I doubt that the HT is on the transformer only the filaments which are probably now in parallel since the other valves are already 6.3V types, but its still a live chassis set.

Cheers

Mike T

[usradcoll1]

The Pilot sets still were built with a lot of US influence. It looks like a Micamold mica capacitor and those generic knobs, so common to many US makes.
Naturally, the heater circuit has been changed to parallel, which is interesting. So, it would be just a heater transformer to furnish the valve heaters and the selenium rectifier to furnish the HT.
Dave, USradcoll1,

[Sideband]

I agree about the mod....its not standard. The underside view shows the rectifier valveholder. It's been modified for parallel valves rather than series. Probably OK BUT I would change that selenium for a silicon diode and series resistor to bring the HT down to normal....and do something with the wiring to it. Alternatively wire it back for series valves, fit the correct rectifier and use a capacitive dropper.

[PJL]

In principle, using a 6.3V transformer for the heater rather than a dropper is a good solution as it substantially reduces the heat dissipation inside the case. I would stick with it and do as Sideband suggested, replace the rectifier with a diode and resistor, and tidy up the wiring.

[Hartley118]

Your set is probably now similar to the Premier Radio and Barton kits. They had parallel heaters, a heater transformer and a selenium rectifier. Good performers. The circuit for these is ‘up top’.

Martin

[cathoderay57]

Hi John, you also said that the wiring around the 6k8g was different to that shown in the circuit you have. I'm curious to know what the difference is (apart from the heater connections as already noted). There should not have been any need to change the other connections to this valve. Cheers, Jerry

[longneck90]

Hello to all. Thanks for all the information from respondents, which I will make use of, as I try to resurrect this 'lovable' radio. As I presume, this radio was once working, I am left wondering about the Cathode connection on V1 being directly connected to earth. In all the circuit diagrams I have, there is a resister (200/220 ohms) connected between cathode and earth. Thanks to all. John.

[stevehertz]

It's too late now, but you can mix Araldite with bakelite filings to make the correct colour. A tip for next time I suppose.

[Cobaltblue]

This is the 1939 Maestro and the Cathode is directly connected to Chassis See snip attached.

Cheers

Mike T

[longneck90]

Hello to all. Thanks to stevehertz the cabinet repair advice. I have only repaired ? this cabinet temporarily, to keep it together, in case I cause further damage. Thanks to Mike T for the circuit snippet of V1. I now believe I have that circuit diagram, but it is not from a Pilot radio. I'll look tomorrow. All the best. John.

[Herald1360]

Originally Posted by Cobaltblue

This is the 1939 Maestro and the Cathode is directly connected to Chassis See snip attached.

That's not a 6K8 valve, though.....

[PJL]

The snippet is from Trader 444 and the valve is a 6A8G heptode.

[longneck90]

Hello to all. Thanks for all the information on this radio. To Herald 1360; Well spotted (6K8G). What it is; I have inserted this different (from 6K8G) valve to balance chassis while examining it, and while I am waiting to save up for the price of a 6K8G. Also thanks to PJL for information about 'Trader' circuit diagram number. I thought I had correct circuit diagram, but... not so. All the best. John.

[Top Cap]

Look out for a Premier Radio to use for cabinet only, there must be many around, some only TRF models. I think other kit suppliers around that time used the same case too.

[longneck90]

Hello to all. To Top Cap; If I can't locate a cabinet, I may try to make a wooden one. I tried a ECH35 and the radio is going loud, sensitive and clear now. I'll install a 6K8G when I get one. Thanks to all. John.

[Sideband]

The original circuit for your radio is in the Radio and TV servicing books Vol 1 and designated as Model 2 (that's not the actual model number, just the publishers way of identifying it). If you click on the Service Data panel at the top of the screen, select P (for Pilot) then 'Little Maestro' and then select 'All to 1953', there are ten models shown there and yours will be number 2. It was originally fitted with a line cord so that has been removed and replaced with a transformer to effectively convert it to Model 3 which is the AC only equivalent. At least having the circuit will enable you to check voltages.

[PJL]

This appears to be the pre-war chassis as it has an energised speaker (Trader 444, model 1 in R&TVS) and would have had a 6A8G but a 6K8G should work too. I have one and it was a mix & match having a PM speaker but the rest of it was the pre-war chassis design.