13-09-2018, 06:51 PM
(This post was last modified: 13-09-2018, 06:55 PM by Murphyv310.)
Hi.
This thread is not so much about the little MW6-2 illustrious history but how it really performed in real life and its possible uses now.
As many here will know I have been the very proud owner of a Decca 1000 projection set for many years. It can display a 4 foot by 3 foot picture onto a remote screen, its a 60 inch display in other words, the very rare Decca 2000 can display a 120 inch picture.
So lets look at this in real terms, the MW6-2 has a 2.5 inch diameter screen, it runs at 25Kv EHT and its illumination is reflected and projected onto an aluminium coated hardboard screen. So the 2.5 inch screen has to have sufficient brightness to fill a 60 inch screen.
If we compare this to the 80's projection sets this is really quite a feat for the time. The offerings from the 80's used three tubes and lenses for each of the primary colours, the tubes had a larger screen area and the luminance was greater due to the use of three tubes, larger surface area and far improved EHT stability. There were big downsides with these projection sets, registration of the three light sources was never perfect, electronic set up was a compromise at best as was electronic and mechanical geometry. Obviously a single tube was by far an easier task.
The downside of the MW6-2 of course projecting was its light output, although the picture on its screen was intensely bright to project onto a 60 inch screen meant that to watch a program it had to be in darkness. In the Decca the CRT faceplate gets blisteringly hot at full pelt and there is no cooling as the Schmitt unit is sealed to stop dust ingress.
This was the systems biggest shortcoming exacerbated by poor EHT regulation. Everyone and their brother ran these sets flat out but that caused picture size changes and focus variations.
I have run my Decca's MW6-2 from a very stable 25kv and it is really good, there is more brightness and no picture size and focus variations.
In comparison to a 80's projection set the Decca has far better focus and geometry but of course we are only using one CRT.
Some of the back projection sets that had a 16 or 20 inch screen were very bright and sharp and of course didn't need to be run flat out so the EHT unit was actually quite stable.
The MW6-2 though can operate at only 6Kv and will focus perfectly, it requires very little scan power and around 65v on the focus coil to give a minute spot. I have decided to give this a try as a monitor, I did have a go before but abandoned the idea at the time as it was around the time of my heart op so I am resurrecting the idea. I've done some tests today and have found that 3v P-P drive to the line coils is enough for full scan.
So these little tubes could well be good for a simple monitor or even a simple LF scope or other monitoring device.
This thread is not so much about the little MW6-2 illustrious history but how it really performed in real life and its possible uses now.
As many here will know I have been the very proud owner of a Decca 1000 projection set for many years. It can display a 4 foot by 3 foot picture onto a remote screen, its a 60 inch display in other words, the very rare Decca 2000 can display a 120 inch picture.
So lets look at this in real terms, the MW6-2 has a 2.5 inch diameter screen, it runs at 25Kv EHT and its illumination is reflected and projected onto an aluminium coated hardboard screen. So the 2.5 inch screen has to have sufficient brightness to fill a 60 inch screen.
If we compare this to the 80's projection sets this is really quite a feat for the time. The offerings from the 80's used three tubes and lenses for each of the primary colours, the tubes had a larger screen area and the luminance was greater due to the use of three tubes, larger surface area and far improved EHT stability. There were big downsides with these projection sets, registration of the three light sources was never perfect, electronic set up was a compromise at best as was electronic and mechanical geometry. Obviously a single tube was by far an easier task.
The downside of the MW6-2 of course projecting was its light output, although the picture on its screen was intensely bright to project onto a 60 inch screen meant that to watch a program it had to be in darkness. In the Decca the CRT faceplate gets blisteringly hot at full pelt and there is no cooling as the Schmitt unit is sealed to stop dust ingress.
This was the systems biggest shortcoming exacerbated by poor EHT regulation. Everyone and their brother ran these sets flat out but that caused picture size changes and focus variations.
I have run my Decca's MW6-2 from a very stable 25kv and it is really good, there is more brightness and no picture size and focus variations.
In comparison to a 80's projection set the Decca has far better focus and geometry but of course we are only using one CRT.
Some of the back projection sets that had a 16 or 20 inch screen were very bright and sharp and of course didn't need to be run flat out so the EHT unit was actually quite stable.
The MW6-2 though can operate at only 6Kv and will focus perfectly, it requires very little scan power and around 65v on the focus coil to give a minute spot. I have decided to give this a try as a monitor, I did have a go before but abandoned the idea at the time as it was around the time of my heart op so I am resurrecting the idea. I've done some tests today and have found that 3v P-P drive to the line coils is enough for full scan.
So these little tubes could well be good for a simple monitor or even a simple LF scope or other monitoring device.
