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Old 17th Apr 2007, 12:02 am   #1
petertheorgan
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Default Bush TV32 poor focus

Hi Everbody

I have got a Bush TV32 ( the grown up version of the Bush TV22 ) which works perfectly apart from one thing.
If I turn the brightness / contrast down to give a picture that is just too dark to watch, the focus is perfect but as soon as I turn either of them up to give normal brightness / contrast , the picture jumps badly out of focus.
Gerry Wells (who got it going for me) thinks that it might be the tube; I believe it should be a Mullard NW 36-24
Has anybody had symptoms like this on a similar tv, and where should I go to attempt to get a replacement tube?
The rest of the television is super, and it would be great to have it in perfect working order.

Look forward to your help
peter

Last edited by Mike Phelan; 1st Feb 2008 at 3:59 pm. Reason: Readability
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Old 17th Apr 2007, 12:29 am   #2
Steve_P
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Default Re: Bush tv 32 focus

Well, if Mr Wells thinks it's the tube, who am I to argue? I did a thing on here a while back that might work. But run it with the brightness and contrast up for a couple of days to see if it comes up by itself first.

https://www.vintage-radio.net/forum/...ad.php?t=15913

It either works or it doesn't!!!

Cheers,

Steve P
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Old 17th Apr 2007, 1:14 am   #3
Duke_Nukem
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Default Re: Bush tv 32 focus

If Gerry thinks it may be the tube then good chance it is.

When adjusting the brightness/contrast, what happens to the picture size ?

TTFN,
Jon
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Old 17th Apr 2007, 8:55 am   #4
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Default Re: Bush tv 32 focus

Hello Peter,
It certainly sounds like the tube especially if the focus 'jumps' out as you turn the brightness up. More a case of very slight 'softness' [microscopic quntity of air in the bulb] as opposed to low emission.
The MW36-24 as with all Mullard tubes is an excellent tube, but we are talking more than 50 years ago. It's a wonder they work at all!

You should be able to find a 14" rectangular tube that will work ok. Mullard MW36-44 Mazda CRM144 and Brimar C14FM are numbers back in my distant past. Generally if it's rectangular, and has a .3amp heater, it can be fitted with a few simple mods. Regards John.
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Old 17th Apr 2007, 9:52 am   #5
peter_scott
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Default Re: Bush tv 32 focus

There have been various threads on re-firing the getter. I wonder if this might help in this case.

https://www.vintage-radio.net/forum/...ghlight=getter

Peter
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Old 17th Apr 2007, 10:23 am   #6
Sean Williams
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Default Re: Bush tv 32 focus

Might have a 14" rect tube here - cant tell the type number though - no labels!

Might be worth a go.....
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Old 17th Apr 2007, 11:27 am   #7
petertheorgan
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Default Re: Bush tv 32 focus

Hi Everbody

Thank you for all your helpful comments, I have had the set running for a couple of hours this am and already it appears to be improving.

I will keep it on for most of today and see what happens; I will try and place a photo on here later but they can be misleading as I have found that to take the best photographs, you need to turn brightness and contrast down.

thank you for all your help so far; will report in later

cheers

peter

Last edited by Mike Phelan; 1st Feb 2008 at 4:02 pm. Reason: Extra commas removed
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Old 17th Apr 2007, 9:58 pm   #8
plumbweiss
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Default Re: Bush tv 32 focus

Sounds like a similar thread about my TV12. I have a TV11 somewhere ( TV12 in wood cab) and I'm tempted to get it going so I can 'compare notes' as it were..and possibly swap bits to prove things. I think my poor focus is shown up particularly by the modern trend of broadcasters to swamp every image in annoying graphics, idents and captions.
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Old 18th Apr 2007, 11:08 pm   #9
petertheorgan
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Default Re: Bush tv 32 focus

Hi

I had the tv running for about 6 hours on and off yesterday, and it appeared to improve. I could turn the brightness and contrast up and the picture stayed in focus.

When I turned the set on today, it was back to square one again ( good dark picture but when brightness turned up, jumped out of focus;
after an hour or so this effect went again, and it has been fine all day.

However I turned it on this evening after a couple of hours rest, and we were back to square one again
When you move the brightness control it does appear to affect the sise of the picture, in particular the width.
The other thing I have noticed when I tried to take a photo of the out of focus screen is when I looked at the photo it appears as if there are two pictures on the screen, one above the other ( like an old colour tv with bad convergence ), which makes me wonder if something is unstable.
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Old 19th Apr 2007, 8:40 am   #10
BassoonBloke
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Smile Re: Bush tv 32 focus

Hi Petertheorgan,

Looking at your pictures, the first as you say appears to be a double picture vertically, but not double horizontally. It just occurs to me that this could be a smoothing cap (hum) problem (which may improve as the cap warms up?) or maybe a bit of ac is sneaking into the frame circuit and causing the blurring effect.
The tube may be dim in the last picture but the quality looks pretty good to me.
I'm not so sure that this is a tube problem, but as you say pictures can be deceiving, so i reserve the right to be wrong !!

Keep up the good work,

Alan.
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Old 19th Apr 2007, 2:51 pm   #11
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Default Re: Bush tv 32 focus

Hi Peter,
have you checked whether it is something silly like a noisy brightness control? Check if the A1 voltage changes, check the EHT rectifier and the line output valve...

Cheers
Andy
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