The Jewel Radio. - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 22nd Jul 2017, 6:49 pm

Presenting a truly unusual radio set, the "Jewel Radio" I reckon this one will be an easy fix. The first job is to repair the cord drive which connects the tuning control to the small drum on the tuning capacitor.
I've never seen this type of variable capacitor before, it's most likely not a standard off the shelf item but was made in-house by the radio's manufacturer.
Another unusual feature is the choice of valves, certainly for a mains only receiver. The first three valves are battery types, DK92 as the frequency changer, good valve for short wave reception. The IF amplifier is a DF91 and the detector and AF amplifier a DAF91. The output valve is an UL41, the 45 volts for the heater comes from a tapping on the secondary of the mains transformer. The 4.5 volts for the filaments of the other valves is supplied from the cathode bias resistor of the UL41. The filaments check out OK but there's a possibility these could be overrun if the coupling capacitor between the AF amplifier and output valve is leaky.
HT rectification is by means of a SenTerCel RM2 metal rectifier. Another metal rectifier exists in the receiver so I'll have to find out what it is used for.
The appearance of my Jewel Radio is similar to the one that is shown in the Radiomuseum website.

http://www.radiomuseum.org/r/jewel_jewel.html

DFWB.

paulsherwin · 22nd Jul 2017, 6:53 pm

What a bizarre design!

Dickie · 22nd Jul 2017, 7:25 pm

There was an article in the BVWS bulletin about these:
http://www.bvws.org.uk/publications/...letin_27_2.pdf (page 20)

I purchased two chassis at the NVCF BVWS bring-and-buy stall this year, apparently after a Museum "clearout". The tuning cap. is a joy to behold.

Dave Moll · 22nd Jul 2017, 7:42 pm

Wan't the "Jewel" one of Gerry Wells' favourites for cloning?

Dickie · 22nd Jul 2017, 8:39 pm

I don't know about "cloning". Reading the article, I think he bought up a lot of redundant stock and finished them off for his friends, whether they wanted one or not (!).

Dave Moll · 22nd Jul 2017, 9:03 pm

Ah, so they weren't really part of the so-called Wells Coated range.

FERNSEH · 22nd Jul 2017, 11:01 pm

It's a weird design but it works surprisingly well, very lively on medium waves and acceptable on long waves. No results on short waves, this might be due to filament voltage supplied to the three 50mA valves being only 3.5V. Another 0,5 to 0.7 volts might start the local oscillator on SW.
That tuning capacitor is a strange thing and is a bit tricky to use.
The coupling capacitor between the DAF91 AF amplifier and the grid of the UL41 was replaced some time ago with a Mullard 0.01mfd polyester mustard.

DFWB.

peter_scott · 22nd Jul 2017, 11:13 pm

What form of aerial does it have? I don't see any signs of a rod or a frame.

Peter

FERNSEH · 23rd Jul 2017, 12:47 am

Hi Peter,
The aerial is nothing more than a piece of wire being only one metre long.
Since my previous post the short waveband has come to life. Romania Radio was coming through loud and clear.

DFWB.

22nd Jul 2017, 6:49 pm	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	The Jewel Radio. Presenting a truly unusual radio set, the "Jewel Radio" I reckon this one will be an easy fix. The first job is to repair the cord drive which connects the tuning control to the small drum on the tuning capacitor. I've never seen this type of variable capacitor before, it's most likely not a standard off the shelf item but was made in-house by the radio's manufacturer. Another unusual feature is the choice of valves, certainly for a mains only receiver. The first three valves are battery types, DK92 as the frequency changer, good valve for short wave reception. The IF amplifier is a DF91 and the detector and AF amplifier a DAF91. The output valve is an UL41, the 45 volts for the heater comes from a tapping on the secondary of the mains transformer. The 4.5 volts for the filaments of the other valves is supplied from the cathode bias resistor of the UL41. The filaments check out OK but there's a possibility these could be overrun if the coupling capacitor between the AF amplifier and output valve is leaky. HT rectification is by means of a SenTerCel RM2 metal rectifier. Another metal rectifier exists in the receiver so I'll have to find out what it is used for. The appearance of my Jewel Radio is similar to the one that is shown in the Radiomuseum website. http://www.radiomuseum.org/r/jewel_jewel.html DFWB. Attached Thumbnails

22nd Jul 2017, 6:53 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,965	Re: The Jewel Radio. What a bizarre design!

22nd Jul 2017, 7:25 pm	#3
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: The Jewel Radio. There was an article in the BVWS bulletin about these: http://www.bvws.org.uk/publications/...letin_27_2.pdf (page 20) I purchased two chassis at the NVCF BVWS bring-and-buy stall this year, apparently after a Museum "clearout". The tuning cap. is a joy to behold. __________________ Regards, Richard, BVWS member

22nd Jul 2017, 7:42 pm	#4
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: The Jewel Radio. Wan't the "Jewel" one of Gerry Wells' favourites for cloning? __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

22nd Jul 2017, 8:39 pm	#5
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: The Jewel Radio. I don't know about "cloning". Reading the article, I think he bought up a lot of redundant stock and finished them off for his friends, whether they wanted one or not (!). __________________ Regards, Richard, BVWS member

22nd Jul 2017, 9:03 pm	#6
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: The Jewel Radio. Ah, so they weren't really part of the so-called Wells Coated range. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

22nd Jul 2017, 11:01 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: The Jewel Radio. It's a weird design but it works surprisingly well, very lively on medium waves and acceptable on long waves. No results on short waves, this might be due to filament voltage supplied to the three 50mA valves being only 3.5V. Another 0,5 to 0.7 volts might start the local oscillator on SW. That tuning capacitor is a strange thing and is a bit tricky to use. The coupling capacitor between the DAF91 AF amplifier and the grid of the UL41 was replaced some time ago with a Mullard 0.01mfd polyester mustard. DFWB.

22nd Jul 2017, 11:13 pm	#8
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: The Jewel Radio. What form of aerial does it have? I don't see any signs of a rod or a frame. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

23rd Jul 2017, 12:47 am	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: The Jewel Radio. Hi Peter, The aerial is nothing more than a piece of wire being only one metre long. Since my previous post the short waveband has come to life. Romania Radio was coming through loud and clear. DFWB.