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Old 26th Jun 2012, 7:06 pm   #1
howard
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Default 1955 Ultra R906 Twin De Luxe mains/battery 4 valve MW/LW portable in crocodile skin c

Hello again,

While I was at the Friedrichshafen HAM radio event last year I saw several German built 1950s portable valve radios in crocodile and snake skin covered cabinets but such radios are a relatively rare sight in the UK, and the Ultra Twin De Luxe is probably the best known UK built model. The cabinet design is almost certainly inspired by the German Akkord Offenbach series of sets first released in 1951 as they are all but identical in appearance. I do like this design, particularly in a snake skin cabinet and as I already have the snake skin version of the Twin De Luxe, I snapped up this crocodile version from a table at the last Harpenden swapmeet for £50 to keep it company. That's quite a lot for a 1950s portable valve radio but this one is mint and original (apart from one valve replaced in 1958, receipt for it included in the sale) and most importantly it has its original lead and plug, but then these do fetch good prices on Ebay, particularly in Germany. Sadly it didn't work on arrival, but it does now. The Ultra service manual for the R906 is available here .....

http://www.service-data.com/section.php/8330/1

I replaced the 0.1uF mains filter wax capacitor on the top of the chassis with a Class X2 and the torpedo shaped 0.001uf coupling capacitor with a Vishay polyester, checked all the dropper resistances, cleaned the volume potentiometer, valve pins/sockets, mains/battery switch and waveband switch with DeoxiT, put a plug on the lead and powered up the set, and nothing. There was no current reaching the set and I discovered that there was no continuity through one of the wires in the mains lead. That's unusual for a 1950s set but then the lead is very thin. I tried fitting a brand new 3 amp two core flex to the plug but without success as the wires were not flexible enough to bend into shape inside the plug so I pinched the lead from a scrap R786 Coronation Twin and fitted that, powered up and the droppers started to warm up, but no sound though even after allowing time for the smoothing capacitors to reform. Both HT and LT voltages measured OK.

Unlike my snake skin R906 this example was full of horrible Hunts mouldseals and little torpedo shaped capacitors so I replaced the lot with Vishay polyesters and then checked all the resistors and replaced a couple which were over 20% high, but the set still didn't work, not a peep. I swapped all the valves, checked the output transformer (primary measured 605 ohms (spec 570 ohms) and secondary 1.5 ohms (spec 0.5 ohms approx)) which was OK, speaker showed correct impedance, LT spot on, HT very good, so what was up ? I eventually found a tag on the output transformer was just touching the metal brace under it, I spotted it sparking, a few seconds later after sorting that out the set sprang into life working extremely well. I tested the now reformed smoothing capacitors and the voltage from the metal rectifier and all were good.

I noticed that when the plug was pushed into its socket that the battery connections were not disconnecting in the switch, so the two screws securing the metal piece onto the end of the paxolin push rod were loosened and the metal piece moved forward a touch so that it pushed the sliding brass connectors clear of the battery connections, and the screws retightened.

The IF was still fine at 471 kHz, RF was then checked and amazingly that was still spot on too ! The set was reassembled, the original valves (all good) put back in, the outer case and trim cleaned with upholstery cleaner and the brass handle ends/vents polished with Brasso, job done.

I like the 1950s Ultra Twin and Troubadour series of radios, they are attractive designs and usually work well after a straightforward overhaul. This one certainly does, it is sensitive on both bands and plays louder than most valve portables of its time. It is a very fiddly set to work on though and one needs to be very careful when handling it when powered up out of its cabinet, make sure that the plug it fitted the right way round so that the chassis isn't live and bear in mind that the chassis is still connected to the mains even when switched off.

Howard
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Old 26th Jun 2012, 9:59 pm   #2
Andy - G8MNM
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Default Re: 1955 Ultra R906 Twin De Luxe mains/battery 4 valve MW/LW portable in crocodile sk

Another nice restoration Howard.
I am part way through the restoration of the snakeskin version.
I have recapped it and cleaned the mains and wave change switches.
It had some woodworm so I have made a new inner panel to replace the eaten one. The case has been treated with woodworm killer and the few holes filled with wax.
I have two crocodile skin ones too but both have damaged case covering.

Andy
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Old 26th Jun 2012, 11:03 pm   #3
bobbyball
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Default Re: 1955 Ultra R906 Twin De Luxe mains/battery 4 valve MW/LW portable in crocodile sk

Well done again Howard, looks like it just came out of the maker's box!

Robert
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Old 27th Jun 2012, 10:01 am   #4
JoshWard
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Default Re: 1955 Ultra R906 Twin De Luxe mains/battery 4 valve MW/LW portable in crocodile sk

Very nice work Howard, I'd love to get hold of the snakeskin version some day, they're just so damn stylish

Josh.
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Old 27th Jun 2012, 1:06 pm   #5
howard
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Default Re: 1955 Ultra R906 Twin De Luxe mains/battery 4 valve MW/LW portable in crocodile sk

Quote:
Originally Posted by Andy - G8MNM View Post
..............
It had some woodworm so I have made a new inner panel to replace the eaten one. The case has been treated with woodworm killer and the few holes filled with wax. I have two crocodile skin ones too but both have damaged case covering.
Andy
Hello Andy,

I hope you eventually manage to get your Twins looking good as they are rather nice, if not to everyone's taste.

The other thing to watch out for with Twins and Troubadours is print peeling off the dials.

Quote:
Originally Posted by bobbyball View Post
Well done again Howard, looks like it just came out of the maker's box!
Robert
Nearly !

Quote:
Originally Posted by JoshWard View Post
Very nice work Howard, I'd love to get hold of the snakeskin version some day, they're just so damn stylish
Josh.
Hello Josh,

The snake skin version is certainly eye catching and I keep mine right next to my computer and it has proved to be very reliable too. I hope you find one, maybe put an ad in the sets wanted column and see if you can acquire one at a sensible price.

Howard
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