MW22-17 and MW22-18 aluminised? - UK Vintage Radio Repair and Restoration Discussion Forum

yagosaga · 25th Aug 2008, 9:39 pm

Hello,

in the PYE LV30, I found a MW22-17 and in the B18t/LV20? I found a MW22-18. I assume, both picture tubes were later replacements.

Both picture tubes have a slight ion spot in the centre of the screen. Both picture tubes have no ion trap. At first glance, I assumed they are aluminised. But I can look from the back on the screen through a small band, and I see that the conus is not silvered like I would expect from an aluminised screen. Where these picture tubes produced with a straight gun and no aluminisation?

Kind regards,
Eckhard

Panrock · 25th Aug 2008, 9:55 pm

According to my data both the MW22-17 and MW22-18 are 'straight' tubes with no ion trap or aluminising. The MW22-18 is distinguished by having an external conducting coating.

Steve

yagosaga · 25th Aug 2008, 10:02 pm

Thank you very much. Do you have an information when the first picture tubes with an ion trap or with an aluminised screen appear?

Eckhard

Panrock · 25th Aug 2008, 10:19 pm

Well, the MW22-16 has an ion trap. I don't know of a 9-inch Mullard tube that is aluminised. Not until RACS that is - we've just had one back in this form.

peter_scott · 25th Aug 2008, 10:52 pm

Mullard MW series tubes with aluminising are:

MW6-2
MW43-69
MW43-80
MW53-20
MW53-80

They all have ion traps except the little MW6-2
I thnk MW22-16 and MW31-16 are the first Mullards with ion traps (and Al.).
Yes, the MW22-17 and MW22-18 are without traps or aluminising and the 18 is meant to have the external coating.

Peter

Duke_Nukem · 25th Aug 2008, 11:22 pm

Quote:

Do you have an information when the first picture tubes with an ion trap...

Well, you'd expect Mullard to be first, but it was actually Cossor. The Cossor 900 was basically their pre-war 1210 rushed out cos they had nothing else to offer after the war, so obviously they were a bit behind in TV. Yet in early 1947 they released the first British television utilising an ion trap, their model 902.

TTFN,
Jon

yagosaga · 26th Aug 2008, 1:39 pm

Hello,

thank you very much for your replies! This is really interesting that the MW22-17 and 18 are non aluminised. The ion spots are not so dark as I would have expected from prewar tv sets.

Is it correct that the MW43-69 and later CRTs were aluminised and have ion traps too?

Kind regards,
Eckhard

FERNSEH · 26th Aug 2008, 4:18 pm

The information in the Mullard Maintenance Manual informs us that the MW31-16 has a clear glass screen and ion trap. This tube is identical to the later MW31-74 except that the 74 has a grey glass filter screen.

The MW31-17 has a clear glass screen, no ion trap and no external coating.
The MW31-18 has a clear glass screen and no ion trap. Va2 max is 7KV

Other Mullard 12" CRTs:
The MW31-14 and 14C have no ion traps, the 14C version has no external aquadag coating. Va2 max 7KV.

The MW31-20 has no external coating and no ion trap. The MW31-21 is similar but has an external coating. Va2 is the the final anode and the max volts is 11KV. A much higher rating compared with other Mullard 12" CRTs

Two other tubes are listed. The MW31-22 and -23 have no ion trap. The MW31-23 has no external coating. Also 11KV for max Va2.

The suggested replacement for all these tubes is the MW31-74. Va2 max 9KV.

The ion trap magnet for so equipped tubes is the IT6.

For the larger tubes such as the MW36-24 and MW43-64 the recommended ion trap magnet is the IT9
There is no mention of any of these tubes having metal backed screens.

DFWB.

FERNSEH · 26th Aug 2008, 5:23 pm

A follow up to my essay about the twelve inch Mullard tubes.

The nine inch CRTs listed in the Mullard Maintenance Manual are the MW22-7, MW22-14 and 14C, the MW22-16, the MW22-17 and 18.

The only CRT to employ an ion trap magnet type IT6 is the MW22-16 which is the recommended replacement for all the other tubes. Final anode volts max is 9.0KV. The others are rated as Va2 max 7KV.

The MW22-14, 16 and 18 have an external coating M, the others are clear glass.

None of these tubes have metal backed screens.

The MW22-7, MW22-14, 14C, have the B8G base, the MW22-16 has the duodecal base. I'm not sure about the MW22-17 and 18, it could be the B12A duodecal base. The 12" versions MW31-17 and 18 have the B8G base.

DFWB.

Heatercathodeshort · 26th Aug 2008, 5:57 pm

Mullard were very late introducing metal backed screens. The first tube to do so [not counting the MW6-2] was the 70 degree 21" MW53-20 first employed around 1955. This was soon followed by the 14" AW36-20 [with electrostatic focus] and the 17" MW43-69.
J.

yagosaga · 27th Aug 2008, 8:28 am

Hello,

thank you all for this high valuable informations. Here in Germany, CRT production started in the early fifties, and most of the CRTs were ion trapped MW36-22 and successors.

With the ion spot, my experience is that the intensity of the ion spot depends on the E.H.T. level. With a low E.H.T. of 2.5 KV, the ion spot is dark and sharp limited. With 6.5 KV and more, the ion spot is only a dimmed slight blurry shadow. I assume that the electrons need a higher energy to penetrate into the phosphor through the ion-coroded layer.

Kind regards,
Eckhard

25th Aug 2008, 9:39 pm	#1
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	MW22-17 and MW22-18 aluminised? Hello, in the PYE LV30, I found a MW22-17 and in the B18t/LV20? I found a MW22-18. I assume, both picture tubes were later replacements. Both picture tubes have a slight ion spot in the centre of the screen. Both picture tubes have no ion trap. At first glance, I assumed they are aluminised. But I can look from the back on the screen through a small band, and I see that the conus is not silvered like I would expect from an aluminised screen. Where these picture tubes produced with a straight gun and no aluminisation? Kind regards, Eckhard

25th Aug 2008, 9:55 pm	#2
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,535	Re: MW22-17 and MW22-18 aluminised? According to my data both the MW22-17 and MW22-18 are 'straight' tubes with no ion trap or aluminising. The MW22-18 is distinguished by having an external conducting coating. Steve __________________ https://www.radiocraft.co.uk

25th Aug 2008, 10:02 pm	#3
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	Re: MW22-17 and MW22-18 aluminised? Thank you very much. Do you have an information when the first picture tubes with an ion trap or with an aluminised screen appear? Eckhard

25th Aug 2008, 10:19 pm	#4
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,535	Re: MW22-17 and MW22-18 aluminised? Well, the MW22-16 has an ion trap. I don't know of a 9-inch Mullard tube that is aluminised. Not until RACS that is - we've just had one back in this form. __________________ https://www.radiocraft.co.uk

25th Aug 2008, 10:52 pm	#5
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: MW22-17 and MW22-18 aluminised? Mullard MW series tubes with aluminising are: MW6-2 MW43-69 MW43-80 MW53-20 MW53-80 They all have ion traps except the little MW6-2 I thnk MW22-16 and MW31-16 are the first Mullards with ion traps (and Al.). Yes, the MW22-17 and MW22-18 are without traps or aluminising and the 18 is meant to have the external coating. Peter

26th Aug 2008, 1:39 pm	#7
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	Re: MW22-17 and MW22-18 aluminised? Hello, thank you very much for your replies! This is really interesting that the MW22-17 and 18 are non aluminised. The ion spots are not so dark as I would have expected from prewar tv sets. Is it correct that the MW43-69 and later CRTs were aluminised and have ion traps too? Kind regards, Eckhard

26th Aug 2008, 4:18 pm	#8
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: MW22-17 and MW22-18 aluminised? The information in the Mullard Maintenance Manual informs us that the MW31-16 has a clear glass screen and ion trap. This tube is identical to the later MW31-74 except that the 74 has a grey glass filter screen. The MW31-17 has a clear glass screen, no ion trap and no external coating. The MW31-18 has a clear glass screen and no ion trap. Va2 max is 7KV Other Mullard 12" CRTs: The MW31-14 and 14C have no ion traps, the 14C version has no external aquadag coating. Va2 max 7KV. The MW31-20 has no external coating and no ion trap. The MW31-21 is similar but has an external coating. Va2 is the the final anode and the max volts is 11KV. A much higher rating compared with other Mullard 12" CRTs Two other tubes are listed. The MW31-22 and -23 have no ion trap. The MW31-23 has no external coating. Also 11KV for max Va2. The suggested replacement for all these tubes is the MW31-74. Va2 max 9KV. The ion trap magnet for so equipped tubes is the IT6. For the larger tubes such as the MW36-24 and MW43-64 the recommended ion trap magnet is the IT9 There is no mention of any of these tubes having metal backed screens. DFWB.

26th Aug 2008, 5:23 pm	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: MW22-17 and MW22-18 aluminised? A follow up to my essay about the twelve inch Mullard tubes. The nine inch CRTs listed in the Mullard Maintenance Manual are the MW22-7, MW22-14 and 14C, the MW22-16, the MW22-17 and 18. The only CRT to employ an ion trap magnet type IT6 is the MW22-16 which is the recommended replacement for all the other tubes. Final anode volts max is 9.0KV. The others are rated as Va2 max 7KV. The MW22-14, 16 and 18 have an external coating M, the others are clear glass. None of these tubes have metal backed screens. The MW22-7, MW22-14, 14C, have the B8G base, the MW22-16 has the duodecal base. I'm not sure about the MW22-17 and 18, it could be the B12A duodecal base. The 12" versions MW31-17 and 18 have the B8G base. DFWB.

26th Aug 2008, 5:57 pm	#10
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: MW22-17 and MW22-18 aluminised? Mullard were very late introducing metal backed screens. The first tube to do so [not counting the MW6-2] was the 70 degree 21" MW53-20 first employed around 1955. This was soon followed by the 14" AW36-20 [with electrostatic focus] and the 17" MW43-69. J.

27th Aug 2008, 8:28 am	#11
yagosaga Retired Dormant Member Join Date: Mar 2005 Location: Braunschweig, Germany Posts: 208	Re: MW22-17 and MW22-18 aluminised? Hello, thank you all for this high valuable informations. Here in Germany, CRT production started in the early fifties, and most of the CRTs were ion trapped MW36-22 and successors. With the ion spot, my experience is that the intensity of the ion spot depends on the E.H.T. level. With a low E.H.T. of 2.5 KV, the ion spot is dark and sharp limited. With 6.5 KV and more, the ion spot is only a dimmed slight blurry shadow. I assume that the electrons need a higher energy to penetrate into the phosphor through the ion-coroded layer. Kind regards, Eckhard