Strong tube or faulty TV?

[19Seventy7]

Hi All

I have a Rediffusion CU2213 with a Westinghouse CRT installed.

I noticed today when making an adjustment how low the brightness and contrast were to get the desired levels, so I turned them both right down, along with colour, and got this result.

I've never seen this before so wonder if it's normal or needs further investigation? I would expect that even with a strong tube turning them all right down should black the screen out to a large extent. Of course I'd love it to be a case of a very strong, hardly used tube, but this seems too strong to me...

The green tint is accentuated by my phone, but is caused by a dodgy pot on the convergence board which is waiting on its replacement, and the slightly low quality test card is due to it being on VHS

Would be interested to hear your thoughts on the matter though

Thanks
'77

[agardiner]

Hi,

From your initial findings and description, it sounds like the A1 adjustment is too high.

[1100 man]

Hi '77,

The range of the brightness control is determined by the settings of the A1 controls. These are the three 'background' controls and are in essence individual brightness controls for each gun. So if they are set too high, even at minimum brightness the overall brightness will be too high.

There is a set up procedure for the A1 controls to ensure each gun cuts off at the correct point. However, as a tube ages, the characteristics of each gun alters to the point where it becomes hard to achieve good tracking between all three guns over the full range of brightness. This shows as a change in background hue as the brightness is varied from min to max.

Setting up a worn tube is always a compromise to achieve the best black & white picture. This often means the A1 controls need to be set higher than they would have been when the tube was new. If the A1's are set too high, flyback lines will be visible.

Manufacturers often included a 'preset brightness' control to get the range of the customer control correct.

It's unlikely your tube is 'too good'! After all, you can't get more than the 100% emission it had when it was new! So it's going to be a case of setting it up correctly to get the best black & white picture you can over the full range of brightness. If that can be achieved with lower A1 settings, so much the better, but if not, there might be a preset brightness control that will help.

Hope that helps,
Cheers
Nick

[19Seventy7]

Hi all, thanks for the replies

I did wonder about the A1s myself, I only really queried it as naturally I've never seen what a really strong tube would look like as I wasn't around back then!

Once I replace that faulty pot I mentioned, I'll go through the set up procedure with it and see what kind of results I get. I'm still hopeful it's got a good tube in it, but we'll soon find out. I'm glad I noticed it this early on as I don't want to over-run the tube.

Will let you know how it goes

Thanks
'77

[agardiner]

From your first photo, the tube looks pretty good, albeit a bit green. I look forward to hearing your results when you have set it up.

[its ur aerial]

I agree with Adrian, it dont look bad for 40 year + Rediffusion MK 1.
I am not sure of the correct method of setting the grayscale on this particular set, but as a general rule, turn the colour of and contrast to minimum then turn up the brilliance to get a raster, then adjust the A1 pots in turn to get a Mono picture as close to black and white as possible, then adj all three customer controls back up to a viewable pic.
I recall the 2213`s being the best of the MK1 series, both for reliability and pic quality .
You've done well their.
PS. I nearly forgot, I recall the collector load resistors of the video O/P transistors being a common fault, I don't think its a problem with yours, but keep it in mind.
PPS. From the pic, it looks like the Purity may be a bit out, degauss the CRT and set that up first.
Ken G6HZG.

[Visualimage]

Wow 2213 Mk1 , this was one of my favourite chassis when I was at rediffusion - this got replaced by the 2217 version using the mk3 push button assembly.
These suffered from leaky A1 gun switches ( I would have thought 95% of these would have been bridged by now! - also the A1 screen pots ( one for each colour ) these tend to arc and bars that color a bit - might also be worth checking the A1 feed resistor - not to sure on Exact voltage but should have approx 1000v one side and 700ish the other ( cannot remember as it's also 40 years ago) - if you are having trouble getting the A1 down and the voltage is still high when adjusting - look for a common resistor to ground - may of gone high.
The Rgb board was fairly reliable with the odd dry joint on the BF337s and the collector load resistors - I also remember this board has drive presets on this too.
Best of luck - it's a pleasure to give advice on one of these and to here it's still working - maybe the tube is a bit soft in its old days -
Has the red reset button survived?? - these went oc and I remember it was a sod to replace - nainly due my soldering iron being a low wattage and the reser button was mounted on the metal chassis!

[19Seventy7]

Hi all

So I decided to have a look at it today before ordering a new pot as it did seem to have some function to it and thought it may be salvageable. I don't know if I adjusted the wrong thing or not (RV301 - green gain and as pictured) but I couldn't get anything to change on screen. I put it back to where it was originally. I then tried the background pots, all of which were fully turned, adjusting these made no difference to the picture either.

Wiggling the green background control can cause the green to cut out completely, leaving me with a magenta picture, this is the pot I mentioned replacing, but now I'm not so tired I realise it's probably not a problem.

I'll explore further tomorrow following the advice given by VisualImage and its ur aerial and let you know how I get on

VisualImage - The red cut out has indeed survived, as have 2 of the 3 A1 switches, though one of them arcs badly when switched off. In the name of originality I have left it in situ as it causes no problems when on. I've included some pictures that you might like to see

[Visualimage]

Lovely condition aswell - hope you get it sorted - like the ferguson 3v16 or 22 - forgot how these looked until I saw this
One other issue with these is the plastic convergence pots - they burn out and when you see a slight convergence error ( if memory works it was red lin) you would go to this pot and it would be stuck solid with no rotation!

[19Seventy7]

Well I thought I should give an update on this set. Unfortunately I've not yet had chance to take a look at it in depth as I've had to totally redo my analogue channel system, which has taken some time to perfect. I didn't want to make any adjustments on this TV with a less than perfect signal. It deserves better than that!

I have also realised it has another, slightly more urgent, fault. After an hour or so it'd start clicking from the back, with the screen jittering with each click, which I think is heat related, as I once had it running for a couple of hours with the back off without a problem.

I found out last night that it was SG807 conducting, which to me looks like the focus module has gone bad. I'm hopeful it's not the tripler, as other than the quick jitter on the bottom half of the picture with the clicks, the picture is solid and doesn't look like an EHT fault is present. R804 tests perfect at 100k.

I'm now keeping my eyes peeled for a focus module to hopefully cure the fault

Thanks
'77

[yampy187]

Originally Posted by 19Seventy7

I found out last night that it was SG807 conducting, which to me looks like the focus module has gone bad. I'm hopeful it's not the tripler, as other than the quick jitter on the bottom half of the picture with the clicks, the picture is solid and doesn't look like an EHT fault is present. R804 tests perfect at 100k.

It may just need the spark gaps cleaning. If there’s any gunk on there it will flash over.

[19Seventy7]

I'd originally dusted it all out with a brush and cotton buds, but maybe it may be better with some contact cleaner or something on a cotton bud?

[its ur aerial]

I would give it a good clean, back in the day many a dead spider was found in a spark gap.
You might also be able to widen the gap.

Ken G6HZG.

[19Seventy7]

I cleaned it again, this time with contact cleaner sprayed on the cotton bud, this seems to have done the trick thankfully! It ran for a couple of hours without sparking up! I clean spark gaps if/when I see them when I first get a set for this reason, but I think I'll be using contact cleaner on them next time. The cotton bud came out filthy! Says a lot for my cleaning.. I'm just thankful the tripler and focus module are okay!

I'm just waiting on another multimeter to turn up and I'll get to sorting this A1 fault. It'll be great to see this TV giving a well set up picture, as it's already got a fantastic picture on it

Thanks
'77

[HamishBoxer]

Just turn the Green A1 pot down to rectify the greyscale, no meter needed.

[19Seventy7]

Oh I should've said, this had little to no effect, so I was going to search out any potentially high value resistors, as mentioned by visualimage in post #7

Thanks
'77

[Vintage Engr]

Hello '77, I didn't realise that you had one of these, I've only just discovered this thread.

I'd left Rediffusion by the time the MK1 colour came out, but was working for Rank. We had a reciprocal engineering agreement with Rediffusion & had hundreds of the MK1 wired version colour in hotels.
At that time I was mainly in the workshop, & so I got lumbered with all the major repairs on these. Eventually, I turned a scruffy white-painted one into a workshop jig, with holes cut in the cabinet, and a Rank/Bush EHT meter screwed to the top of the cabinet! The whole unit was then mounted on a trolley (which is still in my workshop). I have a picture of the jig somewhere, which I will endeavour to find.

The jig made life a lot easier, as the unit was set up permanently, so that I could suddenly leave off repairing colour cameras & VTR's for example, & then go back to the MK 1 to catch up with the vast number of boards & EHT towers that the field engineers were bringing in on a daily basis. Later we switched to the Rank T20 series & modified them for the Rediffusion wired system.

Fond memories, it's all a long time ago.

David.

[Vintage Engr]

After some searching, I've found a rather blurred copy of the Rediffusion/home-made workshop jig. It was taken with an old Zenith, so the quality should have been better!
I've still got the negs somewhere, I will see if there's a close-up.
You've started me on a long memory journey.

I hope you get it fully set up o.k. Somewhere, I have a an original manual, but haven't been able to find it today,
David.

[Graham G3ZVT]

What does it say on the side. Looks like German.

[Vintage Engr]

Rough translation "Don't stick your fingers in here!" - It's pseudo-German, it was my idea of a joke at the time, & as I'd cut the cabinet about & moved things around, was meant as a deterrent.
You can see that the control panel has ben moved to the top of the cabinet, plus the EHT meter, which was permanently connected.

David.