A new radio - UK Vintage Radio Repair and Restoration Discussion Forum

adibrook · 10th Apr 2006, 8:44 pm

A new addition to the collection has just arrived.

It was kindly donated by a member of the forum (thanks if youre reding this!).

It was in workign condition, so i just put a plastic bucket over the smoother cap (i allway do this just incase with equipment new to me) and fired it up. It worked nicely and gave good preformance.

I have no idea what it is, since i dotn have the case. Just a bare shassis. Also, there is no speaker.

1st of all i guess thers the question of what exactly is it? I have some reasonably bad mobile phone pics.

http://img.photobucket.com/albums/v4...ook/radio3.jpg

http://img.photobucket.com/albums/v4...ook/radio4.jpg

The valve lineup is: 6EB6 pentagrid, 6BA6 RF amp, 6AT6 Detector/AVC/af preamp and two 6BW6's for AF o/p. The rectifier is a 5V4G although this may not be original

What confuses me abit is the lack of phase splitter. Two power valves would suggest a p/p output, but there is no phase splitter, unless the single triode is being a phase splitter, but since cathodyn phase splitters have very low gain, i dont think that would work well?

I have herd of circuits where two power valves can be used without a phase splitter, but i allway thought they were very non-liniar, assymetrical, and only really exist as a novelty and a theoretical circuit in some books.

Or maybe the two valves are in paralell s/e?

Also, is it me, or is the valve lineup abit...umm...small? I cant work out weather this is a cheap set or an up-market expensive set? It seems to ahve fetures from both.

Any general info on it, or comments? Thanks.

Sideband · 10th Apr 2006, 10:36 pm

Hi Adi.

No idea what it is...possibly a radiogram chassis....not many domestic radio's with PP output. The 6AT6 is probably being used as a phase splitter...the grid of one 6BW6 being driven from the cathode, the grid of the other 6BW6 being driven from the anode. You can probably tell by looking at the anode and cathode load resistors of the 6AT6. They will probably both be the same value of the order of 100K (maybe anything from 47K to 120K). 6AT6 = EBC90 or DH77.

Rich.

Paul Stenning · 10th Apr 2006, 10:39 pm

Is that white patch on the right side of the tuning scale a logo? If so, perhaps a closer picture of that may be a clue for someone?

adibrook · 10th Apr 2006, 11:40 pm

The logo appears to say Dulci.

There are 4 scales on the tunign scale. The usual long medium and short wave, but also a LOG scale going from 0 to 100.

I thought about the single triode being used as a cathodyn phase splitter, but my own experiments with the idea showed that they have very low gain and usually a pream is needed to drive them from a dc player signal. A demodulated signal must be alot weaker than a cd players output.

ianj · 11th Apr 2006, 2:07 pm

Definately a Dulci replacement radiogram chassis---I have one with FM as well as an em84 magic eye...........................goes well................ianj

quantum · 11th Apr 2006, 2:53 pm

There are other ways of getting p-p working without the use of an extra valve for a phase splitter. Assuming that there isn't a small interstage p-p tranny or p-p choke hidden on the chassis, p-p working can be got in the output stages itself. One easy way is to have the output stage set up as normal for one valve, as if it was single ended output, and then the second valve is joined at the top of the cathode resistor (which is un-bypassed) and the signal grid of this second valve connects to chassis.

The p-p operates because the second valve has its grid negative to its cathode by the amount of the voltage across the cathode resistor, and any increase in the voltage makes its grid even more negative with respect to the cathode so the voltage drops. When a negative signal causes the first valve to lower its current, the associated drop in voltage across the cathode resistor causes the current in the second valve to rise so you get p-p working. The only drawback it that the valves are in class AB, so total output is only twice the normal for a single valve, but I have bulit an amp based on this idea and it does work surprisingly well. There are other ways of phase splitting in the output stages as well.

Of course, without looking at the chassis, it is of course possible that the two 6BW6s are connected in parallel rather than push pull, so no phase splitter would be required. I've only come across one set before which had parallel output valves before though so it is not common...

Nickthedentist · 11th Apr 2006, 10:42 pm

Quote:

Originally Posted by ianj

Definately a Dulci replacement radiogram chassis

So, were these sold without cabinets for people to upgrade their pre-war sets?

jay_oldstuff · 12th Apr 2006, 1:35 pm

A number on the advertizers in WP in the 50/60 sold them so you could upgrade that old pre war radiogram Just thing how many pre war chasis with px4's went in the bin due to these things

Jay

adibrook · 12th Apr 2006, 10:47 pm

wow...sounds like this is an evil shassis

I will probably turn it into an amp or something.

Hunts smoothing bomb · 13th Apr 2006, 2:50 pm

Strange,
I wouldn't have thought the 6bw6's will be in paralell, I think if I remember rightly that a 6bw6's charecteristics are identical to the old octal 6v6, just in a smaller envelope therefor if it is push-pull you should be looking for around 10w audio output.

Regards
Lee

dazzlevision · 13th Apr 2006, 9:46 pm

Hello,

Here's some background on Dulci.

The Dulci Co Ltd, Dulci Works, Tower Road, Pound Lane., Willesden, London (in 1947). In 1953 and 58, they were at 97-99 Villiers Road, London, NW2. They were makers of radios, amplifiers, tape recorders, Band 3 converters and tuner chassis.

In 1959, the company was taken over by Lee Products (Great Britain) Ltd. Lee Products used the "Elpico" brand.

Regards,

Dazzlevision

10th Apr 2006, 8:44 pm	#1
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	A new radio A new addition to the collection has just arrived. It was kindly donated by a member of the forum (thanks if youre reding this!). It was in workign condition, so i just put a plastic bucket over the smoother cap (i allway do this just incase with equipment new to me) and fired it up. It worked nicely and gave good preformance. I have no idea what it is, since i dotn have the case. Just a bare shassis. Also, there is no speaker. 1st of all i guess thers the question of what exactly is it? I have some reasonably bad mobile phone pics. http://img.photobucket.com/albums/v4...ook/radio3.jpg http://img.photobucket.com/albums/v4...ook/radio4.jpg The valve lineup is: 6EB6 pentagrid, 6BA6 RF amp, 6AT6 Detector/AVC/af preamp and two 6BW6's for AF o/p. The rectifier is a 5V4G although this may not be original What confuses me abit is the lack of phase splitter. Two power valves would suggest a p/p output, but there is no phase splitter, unless the single triode is being a phase splitter, but since cathodyn phase splitters have very low gain, i dont think that would work well? I have herd of circuits where two power valves can be used without a phase splitter, but i allway thought they were very non-liniar, assymetrical, and only really exist as a novelty and a theoretical circuit in some books. Or maybe the two valves are in paralell s/e? Also, is it me, or is the valve lineup abit...umm...small? I cant work out weather this is a cheap set or an up-market expensive set? It seems to ahve fetures from both. Any general info on it, or comments? Thanks.

10th Apr 2006, 10:36 pm	#2
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,577	Re: A new radio Hi Adi. No idea what it is...possibly a radiogram chassis....not many domestic radio's with PP output. The 6AT6 is probably being used as a phase splitter...the grid of one 6BW6 being driven from the cathode, the grid of the other 6BW6 being driven from the anode. You can probably tell by looking at the anode and cathode load resistors of the 6AT6. They will probably both be the same value of the order of 100K (maybe anything from 47K to 120K). 6AT6 = EBC90 or DH77. Rich. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

10th Apr 2006, 10:39 pm	#3
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,072	Re: A new radio Is that white patch on the right side of the tuning scale a logo? If so, perhaps a closer picture of that may be a clue for someone? __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

10th Apr 2006, 11:40 pm	#4
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	Re: A new radio The logo appears to say Dulci. There are 4 scales on the tunign scale. The usual long medium and short wave, but also a LOG scale going from 0 to 100. I thought about the single triode being used as a cathodyn phase splitter, but my own experiments with the idea showed that they have very low gain and usually a pream is needed to drive them from a dc player signal. A demodulated signal must be alot weaker than a cd players output.

11th Apr 2006, 2:07 pm	#5
ianj Heptode Join Date: Mar 2003 Location: Cheltenham Spa, Gloucestershire, UK. Posts: 525	Re: A new radio Definately a Dulci replacement radiogram chassis---I have one with FM as well as an em84 magic eye...........................goes well................ianj

11th Apr 2006, 2:53 pm	#6
quantum Retired Dormant Member Join Date: Mar 2003 Location: Birmingham, West Midlands, UK. Posts: 785	Re: A new radio There are other ways of getting p-p working without the use of an extra valve for a phase splitter. Assuming that there isn't a small interstage p-p tranny or p-p choke hidden on the chassis, p-p working can be got in the output stages itself. One easy way is to have the output stage set up as normal for one valve, as if it was single ended output, and then the second valve is joined at the top of the cathode resistor (which is un-bypassed) and the signal grid of this second valve connects to chassis. The p-p operates because the second valve has its grid negative to its cathode by the amount of the voltage across the cathode resistor, and any increase in the voltage makes its grid even more negative with respect to the cathode so the voltage drops. When a negative signal causes the first valve to lower its current, the associated drop in voltage across the cathode resistor causes the current in the second valve to rise so you get p-p working. The only drawback it that the valves are in class AB, so total output is only twice the normal for a single valve, but I have bulit an amp based on this idea and it does work surprisingly well. There are other ways of phase splitting in the output stages as well. Of course, without looking at the chassis, it is of course possible that the two 6BW6s are connected in parallel rather than push pull, so no phase splitter would be required. I've only come across one set before which had parallel output valves before though so it is not common...

12th Apr 2006, 1:35 pm	#8
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: A new radio A number on the advertizers in WP in the 50/60 sold them so you could upgrade that old pre war radiogram Just thing how many pre war chasis with px4's went in the bin due to these things Jay

12th Apr 2006, 10:47 pm	#9
adibrook Retired Dormant Member Join Date: Dec 2004 Location: Weymouth, Dorset, UK. Posts: 377	Re: A new radio wow...sounds like this is an evil shassis I will probably turn it into an amp or something.

13th Apr 2006, 2:50 pm	#10
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: A new radio Strange, I wouldn't have thought the 6bw6's will be in paralell, I think if I remember rightly that a 6bw6's charecteristics are identical to the old octal 6v6, just in a smaller envelope therefor if it is push-pull you should be looking for around 10w audio output. Regards Lee __________________ Lee

13th Apr 2006, 9:46 pm	#11
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: A new radio Hello, Here's some background on Dulci. The Dulci Co Ltd, Dulci Works, Tower Road, Pound Lane., Willesden, London (in 1947). In 1953 and 58, they were at 97-99 Villiers Road, London, NW2. They were makers of radios, amplifiers, tape recorders, Band 3 converters and tuner chassis. In 1959, the company was taken over by Lee Products (Great Britain) Ltd. Lee Products used the "Elpico" brand. Regards, Dazzlevision