I recently acquired a UDISCO model L-5 battery powered five valve TRF radio from 1927. Due to the age of this radio I would like to restore the cabinet on this radio using the original methods. I'm looking for advice or information on restoring the original finish for this radio. Normally for radios of this age I prefer to preserve the original finish but as you can see from the photos the original finish has gone after years of neglect. If anyone has restored a UDISCO radio I would like to know if the original finish was nitrocellulose laquer, shellac or beeswax.

The radio is complete inside minus the valves. It is an Australian made radio so I have written to the Historic Radio Society of Australia to find out if there is any information or possibly a circuit in their archives. I appreciate any help or information on this radio.
Regards, Sam

Hi Sam,

I'm not sure of the finish, but I do have one of these in good condition. I don't have a circuit, but not too hard to trace out. If you need any pictures etc please let me know. Also, what is the serial number of your set (bottom centre of the front panel). The number on my set is 'No. 754A'.

Robert

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Robert

I have a similar Udisco, much the same radio with a slightly different front panel layout. I am fairly sure it is finished with nitro. The finish is shiny so it is not beeswax, which has a more subdued finish.

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A valve a day keeps the transistor away...

Thanks for your help Robert and Brad. The serial number on this set is 890. I am in the process of cleaning and tracing the circuit for this set. May I kindly ask the valve line up and the battery voltages for your set Robert? The valves are missing from my set. I did find the Bakelite base of a B605 but the glass bulb had been broken. I can then look at obtaining valves and building a suitable power supply.
I will do some investigating and find out if Nitrocellulose lacquer is still available Brad. I read that guitar restorers still use it.

Nitro is still available. You may need to go to a specialist paint supplier. You are looking for Wattyl Stylwood. There are a few different gloss levels available (10, 30, 50, 70 and 95%). 70% looks the part.

Ben

I agree, not to use something that is too shiny. 70% is the go.

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A valve a day keeps the transistor away...

Hi Sam,

The valve line up in mine is B605, B615 (detector), B605, B605, and B609. This is what is in my set, but I have not actually had the set working. But I have other sets with this configuration that work well. I have seen the detector replaced with a B625. The A series valves, and 4volt series (B405 etc) would also have been options, as would the DEL series triodes.
Does it look like the 'Ideal' audio transformers have been replaced. My set uses 'Signal' transformers which I believe were made by United Distributors Co (Udisco), or at least sourced for their sets.

Robert

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Robert

I forgot to add that the voltages are the common 20's hook up - 120 volt HT to OP valve via the horn, a tap at 90 volts fed to the first audio anode, and 22 volts to the detector anode. The A voltage according to the valve type (B605 = 6V, B405 = 5V). A- usually connected to B-, but not always! And lastly, a C bias supply which is usually around 4.5 volts. Usually connected positive side to A- and B- and the negative to the grids of the audio valves - often directly to the 'grid' connection of the audio transformer - but you should be able to trace this from the actual connection / terminal posts of the set. Hope this all makes sense.

Robert.

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Robert

I rarely do anything with cabinets I had a customer that wanted a total refurbish of his Table HMV (it has been posted, albeit I will have photos).

There is an antique restorer In Mackay St, Wangaratta that was still using Nitrocellulose at the time, but it is I believe being phased out like anything else that works. This cabinet looked probably better than it did new, after he got through with it.

Nitrocellulose has the problem of self destructing, but the big thing with it is that each layer actually melts into the previous one and it levels really well.

Solvents such as Methylated Spirits (Principally Ethanol) will severely damage it.

Those valves are in the Philips book but I would believe also on Franks Electron Tube Pages. The plot is similar in all of them, some filament valves do have polarity on the filaments as they are part of their bias, the Grid leak is often different (& resistor failed most times) positive side of filament (UX201A RCA data)

Marc

Hi Robert, The audio transformers are DEAL transformers made by AWA. My 1930 AWA Radiola forty five contains very similar DEAL audio transformers. I have checked the continuity of the windings. The first transformer is good but the second audio transformer appears to have an open circuit on the secondary winding. I will check to see if the break is near the start of the winding and repairable. Thankyou for your help with the valve lineup and voltages. This is my first battery TRF set. Most of the information I find on battery voltages for 1920's TRF sets usually deal with American sets with RCA valves.

I have seen how Nitrocellulose can self destruct Marc. I used to operate a community cinema that dated back to 1912. I remember finding some old film cans containing shorts, cartoons and newsreels on 35mm Nitrate film. Some of the film had started to decompose into a sticky brown mess. Nitrate film is extremely flammable and becomes even more volatile as it decomposes. It has been known to self ignite when decomposing in high temperatures with poor ventilation. The projection room was still equipped with a steel fire door, steel fire shutters over the projector port windows and the floor, ceiling and walls were clad with metal and asbestos sheeting. The idea was that if the film ignited in the projector during a screening the fire and smoke were contained in the projection room while the audience were safely evacuated.

Mother used to work in a picture theatre in those days and a cousin was a projectionist. Some funny stories. They had a fireman, but there was no 000 you rang the RSL.

They used the off cuts in sinking ships etc at the movies: Once alight it was self sustaining and you could pour lots of things on it & it would just carry on regardless. That's why they created "Safety Film".

Even if the transformer is open they are often "gettable" I have bought new coupling transformers for 20's sets.

Marc